AAC Codec Leaderboard (FAAC 2.2.0) #90

nschimme · 2026-09-29T19:30:15Z

nschimme
Sep 29, 2026
Maintainer

🎛️ Audio Codec Leaderboard

Run on a Macbook Pro M1 32GB

FAAC 2.2.0
fdk-aac 2.0.3
ffmpeg 9.1 (g3fc4f99a79) with NMR
Apple AAC 27.0 (26A428)

🎙️ Encoder Rankings | 🔊 Decoder Rankings | 📋 Encoder Breakdowns | 📋 Decoder Breakdowns

🎙️ Encoder Leaderboard

Quality scores are objective proxy estimates (Zimtohrli/ViSQOL), not blind ABX listening test results.

Overall Encoder Rankings

Methodology & Ranking Note: Encoders are ranked primarily by 1st Percentile MOS ($P_1$) / 99% Floor MOS (the score threshold that 99% of tested audio clips equal or exceed) to penalize systemic artifacts on difficult audio, with Overall MOS (averaging all scenarios) as tiebreaker. Per-scenario curves (e.g., 48 kHz Average MOS) display average performance on specific subsets and may show different relative standings than the overall floor resilience metric.

Rank	Encoder	Status	1st Percentile MOS	Overall MOS	Scenarios	Stereo Fidelity	Transient Fidelity	Speed (xRT)	Bitrate Error	Peak RAM	ROM (Flash)
🥇 1	FAAC 2.2.0 (6acbe23a)	OK	2.953	4.452	27/33	0.9722	0.9301	506.9x	1.7%	2.3 MB	73.4 KB
🥈 2	fdkaac 1.0.9	OK	2.809	4.424	27/33	0.9825	0.9219	152.9x	1.7%	3.2 MB	940.5 KB
🥉 3	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)	OK	2.121	4.192	27/33	0.9858	0.9020	40.4x	13.8%	17.4 MB	274.5 KB
4	Apple AAC 27.0	OK	1.541	4.380	27/33	0.9801	0.9157	112.1x	6.8%	8.9 MB	100.3 KB

📊 View Per-Scenario Breakdowns & Visualizations

Per-Scenario Breakdown & Visualizations

16 kHz Mono Speech Quality Across Bitrates

xychart-beta
    title "16 kHz Mono Speech Quality across Bitrates (Average MOS)"
    x-axis ["20k", "24k", "voip_24k"]
    y-axis "MOS Score" 3.639 --> 4.159
    line "FAAC 2.2.0" [4.0297, 4.0792, 4.0245]
    line "fdkaac 1.0.9" [3.8448, 3.9409, 3.9438]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [3.7191, 3.8258, 3.7874]
    line "Apple AAC 27.0" [3.7709, 3.9047, 3.8940]

View Detailed 16 kHz Mono Speech Average & Worst MOS Tables

Per-Scenario Average MOS (16 kHz Mono Speech)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
16k_mono_20k	3.771 ██████░░	4.030 ██████░░	3.845 ██████░░	3.719 ██████░░
16k_mono_24k	3.905 ██████░░	4.079 ███████░	3.941 ██████░░	3.826 ██████░░
16k_mono_voip_24k	3.894 ██████░░	4.025 ██████░░	3.944 ██████░░	3.787 ██████░░

Per-Scenario 1st Percentile MOS ($P_1$) (16 kHz Mono Speech)

Note: 1st percentile MOS ($P_1$) score threshold observed across clips in the scenario. Highlights edge-case clip degradation. A 🐛 names the clip when every other encoder scored ≥0.75 MOS higher on that exact clip -- likely a defect specific to this encoder; see Quality Outliers under Issues Worth Investigating below.

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
16k_mono_20k	3.053 █████░░░	3.368 █████░░░	3.164 █████░░░	3.008 █████░░░
16k_mono_24k	3.169 █████░░░	3.446 ██████░░	3.206 █████░░░	3.088 █████░░░
16k_mono_voip_24k	3.270 █████░░░	3.299 █████░░░	3.296 █████░░░	2.923 █████░░░ 🐛

Transient Fidelity (16 kHz Mono Speech)

Note: Measured as 1 / (1 + mean |attack-centroid-shift| ms) across onsets. Higher is truer (attack timing closer to reference).

xychart-beta
    title "Transient Fidelity across Bitrates - 16 kHz Mono Speech (Higher is Better)"
    x-axis ["20k", "24k", "voip_24k"]
    y-axis "Transient Fidelity" 0.8492 --> 0.9638
    line "FAAC 2.2.0" [0.9369, 0.9438, 0.9364]
    line "fdkaac 1.0.9" [0.8692, 0.8977, 0.8921]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [0.8771, 0.9121, 0.9046]
    line "Apple AAC 27.0" [0.8984, 0.9267, 0.9214]

View Detailed Transient Fidelity Table (16 kHz Mono Speech)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
16k_mono_20k	0.8984 ███████░	0.9369 ███████░	0.8692 ███████░	0.8771 ███████░
16k_mono_24k	0.9267 ███████░	0.9438 ████████	0.8977 ███████░	0.9121 ███████░
16k_mono_voip_24k	0.9214 ███████░	0.9364 ███████░	0.8921 ███████░	0.9046 ███████░

Encoding Speed (16 kHz Mono Speech)

Note: Encoding throughput measured in xRealtime. Higher is Better.

xychart-beta
    title "Encoding Speed across Bitrates - 16 kHz Mono Speech (Higher is Better)"
    x-axis ["20k", "24k", "voip_24k"]
    y-axis "Speed (xRT)" 21.35 --> 100
    line "FAAC 2.2.0" [639.0591, 591.3193, 644.4214]
    line "fdkaac 1.0.9" [394.7191, 404.9186, 381.9877]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [77.9885, 80.4293, 78.7161]
    line "Apple AAC 27.0" [142.0263, 145.9709, 147.2673]

Bitrate Accuracy (16 kHz Mono Speech)

Note: Deviation from target bitrate calculated from pure elementary stream audio bytes. Lower is Better.

xychart-beta
    title "Bitrate Accuracy across Bitrates - 16 kHz Mono Speech (Lower is Better)"
    x-axis ["20k", "24k", "voip_24k"]
    y-axis "Bitrate Error (%)" 0 --> 20
    line "FAAC 2.2.0" [7.7665, 3.8011, 2.7304]
    line "fdkaac 1.0.9" [1.9730, 1.9722, 2.0620]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [44.2973, 44.7540, 35.4356]
    line "Apple AAC 27.0" [21.5205, 22.2912, 17.4535]

View Detailed Bitrate Accuracy Table (16 kHz Mono Speech)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
16k_mono_20k	21.5%	7.8%	2.0%	44.3%
16k_mono_24k	22.3%	3.8%	2.0%	44.8%
16k_mono_voip_24k	17.5%	2.7%	2.1%	35.4%

24 kHz Mono Speech Quality Across Bitrates

xychart-beta
    title "24 kHz Mono Speech Quality across Bitrates (Average MOS)"
    x-axis ["28k", "32k"]
    y-axis "MOS Score" 4.195 --> 4.849
    line "FAAC 2.2.0" [4.7341, 4.7695]
    line "fdkaac 1.0.9" [4.3315, 4.3927]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [4.3739, 4.4860]
    line "Apple AAC 27.0" [4.2749, 4.4075]

View Detailed 24 kHz Mono Speech Average & Worst MOS Tables

Per-Scenario Average MOS (24 kHz Mono Speech)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
24k_mono_28k	4.275 ███████░	4.734 ████████	4.331 ███████░	4.374 ███████░
24k_mono_32k	4.408 ███████░	4.769 ████████	4.393 ███████░	4.486 ███████░

Per-Scenario 1st Percentile MOS ($P_1$) (24 kHz Mono Speech)

Note: 1st percentile MOS ($P_1$) score threshold observed across clips in the scenario. Highlights edge-case clip degradation. A 🐛 names the clip when every other encoder scored ≥0.75 MOS higher on that exact clip -- likely a defect specific to this encoder; see Quality Outliers under Issues Worth Investigating below.

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
24k_mono_28k	3.999 ██████░░	4.583 ███████░	4.097 ███████░	4.084 ███████░
24k_mono_32k	4.241 ███████░	4.634 ███████░	4.195 ███████░	4.221 ███████░

Transient Fidelity (24 kHz Mono Speech)

Note: Measured as 1 / (1 + mean |attack-centroid-shift| ms) across onsets. Higher is truer (attack timing closer to reference).

xychart-beta
    title "Transient Fidelity across Bitrates - 24 kHz Mono Speech (Higher is Better)"
    x-axis ["28k", "32k"]
    y-axis "Transient Fidelity" 0.8601 --> 0.9727
    line "FAAC 2.2.0" [0.9464, 0.9527]
    line "fdkaac 1.0.9" [0.8801, 0.8990]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [0.9044, 0.9263]
    line "Apple AAC 27.0" [0.9029, 0.9239]

View Detailed Transient Fidelity Table (24 kHz Mono Speech)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
24k_mono_28k	0.9029 ███████░	0.9464 ████████	0.8801 ███████░	0.9044 ███████░
24k_mono_32k	0.9239 ███████░	0.9527 ████████	0.8990 ███████░	0.9263 ███████░

Encoding Speed (24 kHz Mono Speech)

Note: Encoding throughput measured in xRealtime. Higher is Better.

xychart-beta
    title "Encoding Speed across Bitrates - 24 kHz Mono Speech (Higher is Better)"
    x-axis ["28k", "32k"]
    y-axis "Speed (xRT)" 13.67 --> 100
    line "FAAC 2.2.0" [652.8743, 638.8968]
    line "fdkaac 1.0.9" [367.9668, 358.3244]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [73.4564, 71.7775]
    line "Apple AAC 27.0" [141.4343, 140.7851]

Bitrate Accuracy (24 kHz Mono Speech)

Note: Deviation from target bitrate calculated from pure elementary stream audio bytes. Lower is Better.

xychart-beta
    title "Bitrate Accuracy across Bitrates - 24 kHz Mono Speech (Lower is Better)"
    x-axis ["28k", "32k"]
    y-axis "Bitrate Error (%)" 0 --> 20
    line "FAAC 2.2.0" [2.5820, 8.3479]
    line "fdkaac 1.0.9" [1.3142, 1.3148]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [45.3130, 45.3293]
    line "Apple AAC 27.0" [26.3808, 26.6170]

View Detailed Bitrate Accuracy Table (24 kHz Mono Speech)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
24k_mono_28k	26.4%	2.6%	1.3%	45.3%
24k_mono_32k	26.6%	8.3%	1.3%	45.3%

32 kHz Stereo Quality Across Bitrates

xychart-beta
    title "32 kHz Stereo Quality across Bitrates (Average MOS)"
    x-axis ["16k", "48k", "64k", "80k", "96k"]
    y-axis "MOS Score" 1.227 --> 5
    line "FAAC 2.2.0" [2.9828, 4.2220, 4.4615, 4.6062, 4.7139]
    line "fdkaac 1.0.9" [2.8274, 4.2448, 4.4726, 4.6513, 4.7536]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [2.4491, 4.0133, 4.3685, 4.5473, 4.6837]
    line "Apple AAC 27.0" [1.5498, 4.2250, 4.4663, 4.6803, 4.7782]

View Detailed 32 kHz Stereo Average & Worst MOS Tables

Per-Scenario Average MOS (32 kHz Stereo)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
32k_stereo_16k	1.550 ██░░░░░░	2.125 ███░░░░░ *	2.012 ███░░░░░ *	2.449 ████░░░░
32k_stereo_48k	2.962 █████░░░ *	4.222 ███████░	3.137 █████░░░ *	4.013 ██████░░
32k_stereo_64k	4.076 ███████░ *	4.462 ███████░	4.381 ███████░ *	4.369 ███████░
32k_stereo_80k	4.680 ███████░	4.606 ███████░	4.651 ███████░	4.547 ███████░
32k_stereo_96k	4.778 ████████	4.714 ████████	4.754 ████████	4.684 ███████░

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
32k_stereo_16k	N/A	2.983 █████░░░	2.451 ████░░░░ *
32k_stereo_48k	4.225 ███████░	4.061 ██████░░ *	4.245 ███████░
32k_stereo_64k	4.466 ███████░	4.274 ███████░ *	4.473 ███████░
32k_stereo_80k	N/A	4.376 ███████░ *	4.547 ███████░ *
32k_stereo_96k	N/A	4.439 ███████░ *	4.587 ███████░ *

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
32k_stereo_16k	N/A	2.827 █████░░░
32k_stereo_48k	3.605 ██████░░ *	3.584 ██████░░ *
32k_stereo_64k	N/A	3.615 ██████░░ *
32k_stereo_80k	N/A	3.619 ██████░░ *
32k_stereo_96k	N/A	3.623 ██████░░ *

Per-Scenario 1st Percentile MOS ($P_1$) (32 kHz Stereo)

Note: 1st percentile MOS ($P_1$) score threshold observed across clips in the scenario. Highlights edge-case clip degradation. A 🐛 names the clip when every other encoder scored ≥0.75 MOS higher on that exact clip -- likely a defect specific to this encoder; see Quality Outliers under Issues Worth Investigating below.

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
32k_stereo_16k	1.049 ██░░░░░░ 🐛	1.667 ███░░░░░	1.539 ██░░░░░░	1.826 ███░░░░░
32k_stereo_48k	2.354 ████░░░░ 🐛	3.833 ██████░░	2.550 ████░░░░ 🐛	3.075 █████░░░
32k_stereo_64k	3.572 ██████░░	4.052 ██████░░	4.077 ███████░	3.465 ██████░░ 🐛
32k_stereo_80k	4.306 ███████░	4.277 ███████░	4.423 ███████░	3.637 ██████░░ 🐛
32k_stereo_96k	4.440 ███████░	4.456 ███████░	4.586 ███████░	3.893 ██████░░

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
32k_stereo_16k	N/A	2.138 ███░░░░░	1.901 ███░░░░░
32k_stereo_48k	3.449 ██████░░	3.492 ██████░░	3.657 ██████░░
32k_stereo_64k	3.863 ██████░░	3.745 ██████░░	4.134 ███████░
32k_stereo_80k	N/A	3.855 ██████░░	4.248 ███████░
32k_stereo_96k	N/A	3.906 ██████░░	4.291 ███████░

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
32k_stereo_16k	N/A	1.798 ███░░░░░
32k_stereo_48k	2.301 ████░░░░ 🐛	2.196 ████░░░░ 🐛
32k_stereo_64k	N/A	2.199 ████░░░░ 🐛
32k_stereo_80k	N/A	2.199 ████░░░░ 🐛
32k_stereo_96k	N/A	2.201 ████░░░░ 🐛

* Italicized scores indicate sub-optimal profile performance superseded by another profile from the same encoder at this bitrate.

Stereo Image Fidelity (32 kHz Stereo)

Note: Measured as 1.0 - |Coherence(Ref) - Coherence(Deg)|. Higher is truer (closer to reference stereo image).

xychart-beta
    title "Stereo Image Fidelity across Bitrates - 32 kHz Stereo (Higher is Better)"
    x-axis ["16k", "48k", "64k", "80k", "96k"]
    y-axis "Stereo Fidelity" 0.8206 --> 1
    line "FAAC 2.2.0" [0.8558, 0.9477, 0.9857, 0.9845, 0.9872]
    line "fdkaac 1.0.9" [0.8406, 0.9878, 0.9900, 0.9898, 0.9926]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [0.9616, 0.9827, 0.9901, 0.9929, 0.9945]
    line "Apple AAC 27.0" [0.9386, 0.9823, 0.9877, 0.9880, 0.9911]

View Detailed Stereo Fidelity Table (32 kHz Stereo)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
32k_stereo_16k	0.9386 ████████	0.6209 █████░░░	0.9279 ███████░	0.9616 ████████
32k_stereo_48k	0.9822 ████████	0.9477 ████████	0.9860 ████████	0.9827 ████████
32k_stereo_64k	0.9843 ████████	0.9857 ████████	0.9881 ████████	0.9901 ████████
32k_stereo_80k	0.9880 ████████	0.9845 ████████	0.9898 ████████	0.9929 ████████
32k_stereo_96k	0.9911 ████████	0.9872 ████████	0.9926 ████████	0.9945 ████████

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
32k_stereo_16k	N/A	0.8558 ███████░	0.9417 ████████
32k_stereo_48k	0.9823 ████████	0.9800 ████████	0.9878 ████████
32k_stereo_64k	0.9877 ████████	0.9856 ████████	0.9900 ████████
32k_stereo_80k	N/A	0.9793 ████████	0.9910 ████████
32k_stereo_96k	N/A	0.9849 ████████	0.9917 ████████

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
32k_stereo_16k	N/A	0.8406 ███████░
32k_stereo_48k	0.8645 ███████░	0.8440 ███████░
32k_stereo_64k	N/A	0.8440 ███████░
32k_stereo_80k	N/A	0.8440 ███████░
32k_stereo_96k	N/A	0.8441 ███████░

Transient Fidelity (32 kHz Stereo)

Note: Measured as 1 / (1 + mean |attack-centroid-shift| ms) across onsets. Higher is truer (attack timing closer to reference).

xychart-beta
    title "Transient Fidelity across Bitrates - 32 kHz Stereo (Higher is Better)"
    x-axis ["16k", "48k", "64k", "80k", "96k"]
    y-axis "Transient Fidelity" 0.6947 --> 0.9878
    line "FAAC 2.2.0" [0.7325, 0.9045, 0.9353, 0.9505, 0.9587]
    line "fdkaac 1.0.9" [0.8117, 0.9087, 0.9259, 0.9390, 0.9534]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [0.7191, 0.8710, 0.9318, 0.9503, 0.9633]
    line "Apple AAC 27.0" [0.7773, 0.8932, 0.9254, 0.9094, 0.9314]

View Detailed Transient Fidelity Table (32 kHz Stereo)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
32k_stereo_16k	0.7773 ██████░░	0.5621 ████░░░░	0.7586 ██████░░	0.7191 ██████░░
32k_stereo_48k	0.8774 ███████░	0.9045 ███████░	0.8962 ███████░	0.8710 ███████░
32k_stereo_64k	0.8891 ███████░	0.9353 ███████░	0.9190 ███████░	0.9318 ███████░
32k_stereo_80k	0.9094 ███████░	0.9505 ████████	0.9390 ████████	0.9503 ████████
32k_stereo_96k	0.9314 ███████░	0.9587 ████████	0.9534 ████████	0.9633 ████████

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
32k_stereo_16k	N/A	0.7325 ██████░░	0.7695 ██████░░
32k_stereo_48k	0.8932 ███████░	0.9039 ███████░	0.9087 ███████░
32k_stereo_64k	0.9254 ███████░	0.9221 ███████░	0.9259 ███████░
32k_stereo_80k	N/A	0.9255 ███████░	0.9343 ███████░
32k_stereo_96k	N/A	0.9322 ███████░	0.9386 ████████

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
32k_stereo_16k	N/A	0.8117 ██████░░
32k_stereo_48k	0.8801 ███████░	0.8768 ███████░
32k_stereo_64k	N/A	0.8774 ███████░
32k_stereo_80k	N/A	0.8789 ███████░
32k_stereo_96k	N/A	0.8810 ███████░

Encoding Speed (32 kHz Stereo)

Note: Encoding throughput measured in xRealtime. Higher is Better.

xychart-beta
    title "Encoding Speed across Bitrates - 32 kHz Stereo (Higher is Better)"
    x-axis ["16k", "48k", "64k", "80k", "96k"]
    y-axis "Speed (xRT)" 0 --> 100
    line "FAAC 2.2.0" [600.7091, 583.5982, 528.4411, 557.0522, 544.0627]
    line "fdkaac 1.0.9" [190.4136, 113.4672, 113.8784, 120.8199, 117.7563]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [40.9346, 38.3646, 37.8319, 35.6218, 34.2138]
    line "Apple AAC 27.0" [171.1924, 118.1539, 121.5872, 112.2117, 110.3071]

Bitrate Accuracy (32 kHz Stereo)

Note: Deviation from target bitrate calculated from pure elementary stream audio bytes. Lower is Better.

xychart-beta
    title "Bitrate Accuracy across Bitrates - 32 kHz Stereo (Lower is Better)"
    x-axis ["16k", "48k", "64k", "80k", "96k"]
    y-axis "Bitrate Error (%)" 0 --> 20
    line "FAAC 2.2.0" [4.5095, 0.7511, 0.6437, 0.6545, 0.6169]
    line "fdkaac 1.0.9" [3.7843, 2.3146, 2.1370, 1.4331, 1.2178]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [80.0111, 1.6726, 1.3434, 1.1255, 1.0194]
    line "Apple AAC 27.0" [3.5376, 3.6652, 3.3690, 3.9045, 2.4709]

View Detailed Bitrate Accuracy Table (32 kHz Stereo)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
32k_stereo_16k	3.5%	6.6%	8.1%	80.0%
32k_stereo_48k	1.9%	0.8%	1.9%	1.7%
32k_stereo_64k	2.2%	0.6%	1.7%	1.3%
32k_stereo_80k	3.9%	0.7%	1.4%	1.1%
32k_stereo_96k	2.5%	0.6%	1.2%	1.0%

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
32k_stereo_16k	N/A	4.5%	6.4%
32k_stereo_48k	3.7%	1.1%	2.3%
32k_stereo_64k	3.4%	0.5%	2.1%
32k_stereo_80k	N/A	0.3%	2.0%
32k_stereo_96k	N/A	0.3%	1.9%

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
32k_stereo_16k	N/A	3.8%
32k_stereo_48k	3.3%	2.6%
32k_stereo_64k	N/A	2.6%
32k_stereo_80k	N/A	2.6%
32k_stereo_96k	N/A	2.6%

44.1 kHz Stereo Quality Across Bitrates

xychart-beta
    title "44.1 kHz Stereo Quality across Bitrates (Average MOS)"
    x-axis ["64k", "128k", "160k", "192k", "256k"]
    y-axis "MOS Score" 4.228 --> 5
    line "FAAC 2.2.0" [4.4150, 4.8386, 4.9096, 4.9470, 4.9798]
    line "fdkaac 1.0.9" [4.5208, 4.8357, 4.8875, 4.9319, 4.9571]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [4.3078, 4.7905, 4.8734, 4.9239, 4.9594]
    line "Apple AAC 27.0" [4.5269, 4.8699, 4.9319, 4.9645, 4.9853]

View Detailed 44.1 kHz Stereo Average & Worst MOS Tables

Per-Scenario Average MOS (44.1 kHz Stereo)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
44k1_stereo_64k	4.033 ██████░░ *	4.398 ███████░ *	4.306 ███████░ *	4.308 ███████░
44k1_stereo_128k	4.870 ████████	4.839 ████████	4.836 ████████	4.791 ████████
44k1_stereo_160k	4.932 ████████	4.910 ████████	4.887 ████████	4.873 ████████
44k1_stereo_192k	4.964 ████████	4.947 ████████	4.932 ████████	4.924 ████████
44k1_stereo_256k	4.985 ████████	4.980 ████████	4.957 ████████	4.959 ████████

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
44k1_stereo_64k	4.527 ███████░	4.415 ███████░	4.521 ███████░
44k1_stereo_128k	N/A	4.784 ████████ *	4.770 ████████ *
44k1_stereo_160k	N/A	4.844 ████████ *	4.791 ████████ *
44k1_stereo_192k	N/A	4.865 ████████ *	4.799 ████████ *
44k1_stereo_256k	N/A	4.875 ████████ *	4.803 ████████ *

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
44k1_stereo_64k	N/A	3.744 ██████░░ *
44k1_stereo_128k	N/A	3.766 ██████░░ *
44k1_stereo_160k	N/A	3.766 ██████░░ *
44k1_stereo_192k	N/A	3.766 ██████░░ *
44k1_stereo_256k	N/A	3.766 ██████░░ *

Per-Scenario 1st Percentile MOS ($P_1$) (44.1 kHz Stereo)

Note: 1st percentile MOS ($P_1$) score threshold observed across clips in the scenario. Highlights edge-case clip degradation. A 🐛 names the clip when every other encoder scored ≥0.75 MOS higher on that exact clip -- likely a defect specific to this encoder; see Quality Outliers under Issues Worth Investigating below.

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
44k1_stereo_64k	3.490 ██████░░ 🐛	3.841 ██████░░	3.874 ██████░░	3.555 ██████░░
44k1_stereo_128k	4.723 ████████	4.662 ███████░	4.648 ███████░	4.130 ███████░
44k1_stereo_160k	4.837 ████████	4.806 ████████	4.717 ████████	4.409 ███████░
44k1_stereo_192k	4.917 ████████	4.874 ████████	4.828 ████████	4.639 ███████░
44k1_stereo_256k	4.962 ████████	4.951 ████████	4.884 ████████	4.824 ████████

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
44k1_stereo_64k	3.973 ██████░░	4.064 ███████░	4.187 ███████░
44k1_stereo_128k	N/A	4.606 ███████░	4.594 ███████░
44k1_stereo_160k	N/A	4.655 ███████░	4.617 ███████░
44k1_stereo_192k	N/A	4.682 ███████░	4.624 ███████░
44k1_stereo_256k	N/A	4.697 ████████	4.630 ███████░

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
44k1_stereo_64k	N/A	2.366 ████░░░░ 🐛
44k1_stereo_128k	N/A	2.372 ████░░░░ 🐛
44k1_stereo_160k	N/A	2.371 ████░░░░ 🐛
44k1_stereo_192k	N/A	2.371 ████░░░░ 🐛
44k1_stereo_256k	N/A	2.371 ████░░░░ 🐛

* Italicized scores indicate sub-optimal profile performance superseded by another profile from the same encoder at this bitrate.

Stereo Image Fidelity (44.1 kHz Stereo)

Note: Measured as 1.0 - |Coherence(Ref) - Coherence(Deg)|. Higher is truer (closer to reference stereo image).

xychart-beta
    title "Stereo Image Fidelity across Bitrates - 44.1 kHz Stereo (Higher is Better)"
    x-axis ["64k", "128k", "160k", "192k", "256k"]
    y-axis "Stereo Fidelity" 0.9629 --> 1
    line "FAAC 2.2.0" [0.9829, 0.9922, 0.9953, 0.9959, 0.9971]
    line "fdkaac 1.0.9" [0.9899, 0.9949, 0.9955, 0.9962, 0.9965]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [0.9863, 0.9947, 0.9962, 0.9969, 0.9976]
    line "Apple AAC 27.0" [0.9857, 0.9934, 0.9950, 0.9960, 0.9970]

View Detailed Stereo Fidelity Table (44.1 kHz Stereo)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
44k1_stereo_64k	0.9816 ████████	0.9829 ████████	0.9859 ████████	0.9863 ████████
44k1_stereo_128k	0.9934 ████████	0.9922 ████████	0.9949 ████████	0.9947 ████████
44k1_stereo_160k	0.9950 ████████	0.9953 ████████	0.9955 ████████	0.9962 ████████
44k1_stereo_192k	0.9960 ████████	0.9959 ████████	0.9962 ████████	0.9969 ████████
44k1_stereo_256k	0.9970 ████████	0.9971 ████████	0.9965 ████████	0.9976 ████████

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
44k1_stereo_64k	0.9857 ████████	0.9829 ████████	0.9899 ████████
44k1_stereo_128k	N/A	0.9930 ████████	0.9941 ████████
44k1_stereo_160k	N/A	0.9958 ████████	0.9945 ████████
44k1_stereo_192k	N/A	0.9962 ████████	0.9948 ████████
44k1_stereo_256k	N/A	0.9965 ████████	0.9951 ████████

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
44k1_stereo_64k	N/A	0.8398 ███████░
44k1_stereo_128k	N/A	0.8399 ███████░
44k1_stereo_160k	N/A	0.8399 ███████░
44k1_stereo_192k	N/A	0.8399 ███████░
44k1_stereo_256k	N/A	0.8399 ███████░

Transient Fidelity (44.1 kHz Stereo)

Note: Measured as 1 / (1 + mean |attack-centroid-shift| ms) across onsets. Higher is truer (attack timing closer to reference).

xychart-beta
    title "Transient Fidelity across Bitrates - 44.1 kHz Stereo (Higher is Better)"
    x-axis ["64k", "128k", "160k", "192k", "256k"]
    y-axis "Transient Fidelity" 0.8818 --> 1
    line "FAAC 2.2.0" [0.9342, 0.9743, 0.9819, 0.9854, 0.9902]
    line "fdkaac 1.0.9" [0.9298, 0.9672, 0.9731, 0.9781, 0.9817]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [0.9175, 0.9728, 0.9799, 0.9846, 0.9903]
    line "Apple AAC 27.0" [0.9018, 0.9556, 0.9683, 0.9799, 0.9881]

View Detailed Transient Fidelity Table (44.1 kHz Stereo)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
44k1_stereo_64k	0.8856 ███████░	0.9239 ███████░	0.9102 ███████░	0.9175 ███████░
44k1_stereo_128k	0.9556 ████████	0.9743 ████████	0.9672 ████████	0.9728 ████████
44k1_stereo_160k	0.9683 ████████	0.9819 ████████	0.9731 ████████	0.9799 ████████
44k1_stereo_192k	0.9799 ████████	0.9854 ████████	0.9781 ████████	0.9846 ████████
44k1_stereo_256k	0.9881 ████████	0.9902 ████████	0.9817 ████████	0.9903 ████████

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
44k1_stereo_64k	0.9018 ███████░	0.9342 ███████░	0.9298 ███████░
44k1_stereo_128k	N/A	0.9653 ████████	0.9581 ████████
44k1_stereo_160k	N/A	0.9713 ████████	0.9617 ████████
44k1_stereo_192k	N/A	0.9746 ████████	0.9638 ████████
44k1_stereo_256k	N/A	0.9771 ████████	0.9668 ████████

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
44k1_stereo_64k	N/A	0.8880 ███████░
44k1_stereo_128k	N/A	0.8921 ███████░
44k1_stereo_160k	N/A	0.8920 ███████░
44k1_stereo_192k	N/A	0.8920 ███████░
44k1_stereo_256k	N/A	0.8920 ███████░

Encoding Speed (44.1 kHz Stereo)

Note: Encoding throughput measured in xRealtime. Higher is Better.

xychart-beta
    title "Encoding Speed across Bitrates - 44.1 kHz Stereo (Higher is Better)"
    x-axis ["64k", "128k", "160k", "192k", "256k"]
    y-axis "Speed (xRT)" 0 --> 100
    line "FAAC 2.2.0" [481.1670, 473.9142, 437.5758, 418.8853, 424.4584]
    line "fdkaac 1.0.9" [88.9688, 103.9320, 94.9915, 96.3698, 90.0045]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [34.8688, 27.3080, 25.9953, 27.8717, 27.2397]
    line "Apple AAC 27.0" [106.2185, 91.2387, 94.4879, 93.3297, 90.6960]

Bitrate Accuracy (44.1 kHz Stereo)

Note: Deviation from target bitrate calculated from pure elementary stream audio bytes. Lower is Better.

xychart-beta
    title "Bitrate Accuracy across Bitrates - 44.1 kHz Stereo (Lower is Better)"
    x-axis ["64k", "128k", "160k", "192k", "256k"]
    y-axis "Bitrate Error (%)" 0.1868 --> 3.508
    line "FAAC 2.2.0" [0.5972, 0.7164, 0.7474, 0.7565, 0.7779]
    line "fdkaac 1.0.9" [1.7074, 0.8097, 0.7077, 0.6446, 0.5868]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [1.1193, 0.8389, 0.7414, 0.7925, 0.6735]
    line "Apple AAC 27.0" [3.1011, 2.3146, 2.7496, 3.1075, 2.6353]

View Detailed Bitrate Accuracy Table (44.1 kHz Stereo)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
44k1_stereo_64k	2.3%	0.7%	1.7%	1.1%
44k1_stereo_128k	2.3%	0.7%	0.8%	0.8%
44k1_stereo_160k	2.7%	0.7%	0.7%	0.7%
44k1_stereo_192k	3.1%	0.8%	0.6%	0.8%
44k1_stereo_256k	2.6%	0.8%	0.6%	0.7%

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
44k1_stereo_64k	3.1%	0.6%	1.7%
44k1_stereo_128k	N/A	0.4%	1.4%
44k1_stereo_160k	N/A	0.5%	1.4%
44k1_stereo_192k	N/A	0.8%	1.4%
44k1_stereo_256k	N/A	8.2%	1.4%

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
44k1_stereo_64k	N/A	1.9%
44k1_stereo_128k	N/A	1.9%
44k1_stereo_160k	N/A	15.8%
44k1_stereo_192k	N/A	29.8%
44k1_stereo_256k	N/A	47.4%

48 kHz Stereo Quality Across Bitrates

xychart-beta
    title "48 kHz Stereo Quality across Bitrates (Average MOS)"
    x-axis ["24k", "32k", "40k", "48k", "56k", "64k", "96k", "128k", "160k", "192k", "256k", "320k"]
    y-axis "MOS Score" 2.259 --> 5
    line "FAAC 2.2.0" [3.4271, 3.8117, 4.0201, 4.1719, 4.3089, 4.4137, 4.6872, 4.8336, 4.9053, 4.9427, 4.9761, 4.9889]
    line "fdkaac 1.0.9" [3.3620, 3.8615, 4.1457, 4.2650, 4.4403, 4.5249, 4.7366, 4.8331, 4.8856, 4.9300, 4.9553, 4.9624]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [2.5145, 2.5077, 2.6667, 3.8327, 4.1293, 4.2786, 4.6262, 4.7918, 4.8745, 4.9241, 4.9626, 4.9749]
    line "Apple AAC 27.0" [3.3777, 3.8166, 4.1353, 4.2713, 4.4168, 4.5446, 4.7338, 4.8670, 4.9304, 4.9635, 4.9833, 4.9932]

View Detailed 48 kHz Stereo Average & Worst MOS Tables

Per-Scenario Average MOS (48 kHz Stereo)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
48k_stereo_24k	1.626 ███░░░░░ *	2.715 ████░░░░ *	2.255 ████░░░░ *	2.515 ████░░░░
48k_stereo_32k	2.581 ████░░░░ *	3.454 ██████░░ *	2.660 ████░░░░ *	2.508 ████░░░░
48k_stereo_40k	2.966 █████░░░ *	3.868 ██████░░ *	2.856 █████░░░ *	2.667 ████░░░░
48k_stereo_48k	2.949 █████░░░ *	4.110 ███████░ *	3.046 █████░░░ *	3.833 ██████░░
48k_stereo_56k	3.465 ██████░░ *	4.258 ███████░ *	4.113 ███████░ *	4.129 ███████░
48k_stereo_64k	4.029 ██████░░ *	4.379 ███████░ *	4.250 ███████░ *	4.279 ███████░
48k_stereo_96k	4.734 ████████	4.687 ███████░	4.728 ████████	4.626 ███████░
48k_stereo_128k	4.867 ████████	4.834 ████████	4.833 ████████	4.792 ████████
48k_stereo_160k	4.930 ████████	4.905 ████████	4.886 ████████	4.874 ████████
48k_stereo_192k	4.964 ████████	4.943 ████████	4.930 ████████	4.924 ████████
48k_stereo_256k	4.983 ████████	4.976 ████████	4.955 ████████	4.963 ████████
48k_stereo_320k	4.993 ████████	4.989 ████████	4.962 ████████	4.975 ████████

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
48k_stereo_24k	2.675 ████░░░░ *	3.427 █████░░░	3.362 █████░░░
48k_stereo_32k	3.817 ██████░░	3.812 ██████░░	3.862 ██████░░
48k_stereo_40k	4.135 ███████░	4.020 ██████░░	4.146 ███████░
48k_stereo_48k	4.271 ███████░	4.172 ███████░	4.265 ███████░
48k_stereo_56k	4.417 ███████░	4.309 ███████░	4.440 ███████░
48k_stereo_64k	4.545 ███████░	4.414 ███████░	4.525 ███████░
48k_stereo_96k	N/A	4.675 ███████░ *	4.737 ████████
48k_stereo_128k	N/A	4.805 ████████ *	4.809 ████████ *
48k_stereo_160k	N/A	4.870 ████████ *	4.837 ████████ *
48k_stereo_192k	N/A	4.897 ████████ *	4.847 ████████ *
48k_stereo_256k	N/A	4.913 ████████ *	4.850 ████████ *
48k_stereo_320k	N/A	4.914 ████████ *	4.853 ████████ *

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
48k_stereo_24k	3.378 █████░░░	3.326 █████░░░ *
48k_stereo_32k	3.584 ██████░░ *	3.544 ██████░░ *
48k_stereo_40k	3.699 ██████░░ *	3.666 ██████░░ *
48k_stereo_48k	3.768 ██████░░ *	3.707 ██████░░ *
48k_stereo_56k	N/A	3.739 ██████░░ *
48k_stereo_64k	N/A	3.754 ██████░░ *
48k_stereo_96k	N/A	3.779 ██████░░ *
48k_stereo_128k	N/A	3.779 ██████░░ *
48k_stereo_160k	N/A	3.781 ██████░░ *
48k_stereo_192k	N/A	3.781 ██████░░ *
48k_stereo_256k	N/A	3.781 ██████░░ *
48k_stereo_320k	N/A	3.781 ██████░░ *

Per-Scenario 1st Percentile MOS ($P_1$) (48 kHz Stereo)

Note: 1st percentile MOS ($P_1$) score threshold observed across clips in the scenario. Highlights edge-case clip degradation. A 🐛 names the clip when every other encoder scored ≥0.75 MOS higher on that exact clip -- likely a defect specific to this encoder; see Quality Outliers under Issues Worth Investigating below.

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
48k_stereo_24k	1.067 ██░░░░░░ 🐛	1.806 ███░░░░░	1.721 ███░░░░░ 🐛	1.921 ███░░░░░
48k_stereo_32k	1.850 ███░░░░░ 🐛	2.225 ████░░░░	2.047 ███░░░░░ 🐛	1.895 ███░░░░░ 🐛
48k_stereo_40k	2.180 ███░░░░░ 🐛	2.796 ████░░░░ 🐛	2.163 ███░░░░░ 🐛	2.066 ███░░░░░ 🐛
48k_stereo_48k	2.321 ████░░░░ 🐛	3.353 █████░░░	2.361 ████░░░░ 🐛	3.068 █████░░░
48k_stereo_56k	2.790 ████░░░░ 🐛	3.689 ██████░░	3.668 ██████░░	3.328 █████░░░ 🐛
48k_stereo_64k	3.515 ██████░░ 🐛	3.782 ██████░░	3.797 ██████░░	3.526 ██████░░
48k_stereo_96k	4.458 ███████░	4.409 ███████░	4.524 ███████░	3.889 ██████░░ 🐛
48k_stereo_128k	4.722 ████████	4.657 ███████░	4.641 ███████░	4.184 ███████░
48k_stereo_160k	4.857 ████████	4.789 ████████	4.712 ████████	4.412 ███████░
48k_stereo_192k	4.918 ████████	4.858 ████████	4.823 ████████	4.611 ███████░
48k_stereo_256k	4.961 ████████	4.934 ████████	4.880 ████████	4.830 ████████
48k_stereo_320k	4.985 ████████	4.973 ████████	4.896 ████████	4.880 ████████

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
48k_stereo_24k	1.863 ███░░░░░ 🐛	2.543 ████░░░░	2.758 ████░░░░
48k_stereo_32k	2.752 ████░░░░	3.119 █████░░░	3.041 █████░░░
48k_stereo_40k	3.488 ██████░░	3.446 ██████░░	3.512 ██████░░
48k_stereo_48k	3.716 ██████░░	3.706 ██████░░	3.842 ██████░░
48k_stereo_56k	3.721 ██████░░	3.878 ██████░░	4.168 ███████░
48k_stereo_64k	3.947 ██████░░	4.023 ██████░░	4.262 ███████░
48k_stereo_96k	N/A	4.477 ███████░	4.533 ███████░
48k_stereo_128k	N/A	4.613 ███████░	4.645 ███████░
48k_stereo_160k	N/A	4.675 ███████░	4.674 ███████░
48k_stereo_192k	N/A	4.722 ████████	4.684 ███████░
48k_stereo_256k	N/A	4.746 ████████	4.688 ████████
48k_stereo_320k	N/A	4.747 ████████	4.690 ████████

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
48k_stereo_24k	2.279 ████░░░░	2.142 ███░░░░░
48k_stereo_32k	2.394 ████░░░░	2.290 ████░░░░ 🐛
48k_stereo_40k	2.465 ████░░░░ 🐛	2.346 ████░░░░ 🐛
48k_stereo_48k	2.492 ████░░░░ 🐛	2.344 ████░░░░ 🐛
48k_stereo_56k	N/A	2.352 ████░░░░ 🐛
48k_stereo_64k	N/A	2.365 ████░░░░ 🐛
48k_stereo_96k	N/A	2.369 ████░░░░ 🐛
48k_stereo_128k	N/A	2.371 ████░░░░ 🐛
48k_stereo_160k	N/A	2.372 ████░░░░ 🐛
48k_stereo_192k	N/A	2.372 ████░░░░ 🐛
48k_stereo_256k	N/A	2.372 ████░░░░ 🐛
48k_stereo_320k	N/A	2.372 ████░░░░ 🐛

* Italicized scores indicate sub-optimal profile performance superseded by another profile from the same encoder at this bitrate.

Stereo Image Fidelity (48 kHz Stereo)

Note: Measured as 1.0 - |Coherence(Ref) - Coherence(Deg)|. Higher is truer (closer to reference stereo image).

xychart-beta
    title "Stereo Image Fidelity across Bitrates - 48 kHz Stereo (Higher is Better)"
    x-axis ["24k", "32k", "40k", "48k", "56k", "64k", "96k", "128k", "160k", "192k", "256k", "320k"]
    y-axis "Stereo Fidelity" 0.8366 --> 1
    line "FAAC 2.2.0" [0.8844, 0.9173, 0.9598, 0.9778, 0.9804, 0.9826, 0.9851, 0.9914, 0.9946, 0.9954, 0.9966, 0.9973]
    line "fdkaac 1.0.9" [0.9532, 0.9721, 0.9817, 0.9849, 0.9872, 0.9894, 0.9929, 0.9947, 0.9953, 0.9959, 0.9963, 0.9966]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [0.9592, 0.9569, 0.9706, 0.9695, 0.9802, 0.9850, 0.9921, 0.9944, 0.9957, 0.9964, 0.9973, 0.9977]
    line "Apple AAC 27.0" [0.8566, 0.9672, 0.9733, 0.9780, 0.9798, 0.9838, 0.9892, 0.9932, 0.9949, 0.9959, 0.9970, 0.9978]

View Detailed Stereo Fidelity Table (48 kHz Stereo)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
48k_stereo_24k	0.9644 ████████	0.6473 █████░░░	0.9336 ███████░	0.9592 ████████
48k_stereo_32k	0.9714 ████████	0.8932 ███████░	0.9573 ████████	0.9569 ████████
48k_stereo_40k	0.9753 ████████	0.9393 ████████	0.9532 ████████	0.9706 ████████
48k_stereo_48k	0.9782 ████████	0.9531 ████████	0.9762 ████████	0.9695 ████████
48k_stereo_56k	0.9780 ████████	0.9553 ████████	0.9772 ████████	0.9802 ████████
48k_stereo_64k	0.9807 ████████	0.9822 ████████	0.9848 ████████	0.9850 ████████
48k_stereo_96k	0.9892 ████████	0.9851 ████████	0.9914 ████████	0.9921 ████████
48k_stereo_128k	0.9932 ████████	0.9914 ████████	0.9947 ████████	0.9944 ████████
48k_stereo_160k	0.9949 ████████	0.9946 ████████	0.9953 ████████	0.9957 ████████
48k_stereo_192k	0.9959 ████████	0.9954 ████████	0.9959 ████████	0.9964 ████████
48k_stereo_256k	0.9970 ████████	0.9966 ████████	0.9963 ████████	0.9973 ████████
48k_stereo_320k	0.9978 ████████	0.9973 ████████	0.9966 ████████	0.9977 ████████

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
48k_stereo_24k	0.9617 ████████	0.8844 ███████░	0.9532 ████████
48k_stereo_32k	0.9672 ████████	0.9173 ███████░	0.9721 ████████
48k_stereo_40k	0.9733 ████████	0.9598 ████████	0.9817 ████████
48k_stereo_48k	0.9780 ████████	0.9778 ████████	0.9849 ████████
48k_stereo_56k	0.9798 ████████	0.9804 ████████	0.9872 ████████
48k_stereo_64k	0.9838 ████████	0.9826 ████████	0.9894 ████████
48k_stereo_96k	N/A	0.9806 ████████	0.9929 ████████
48k_stereo_128k	N/A	0.9926 ████████	0.9941 ████████
48k_stereo_160k	N/A	0.9960 ████████	0.9944 ████████
48k_stereo_192k	N/A	0.9964 ████████	0.9949 ████████
48k_stereo_256k	N/A	0.9967 ████████	0.9950 ████████
48k_stereo_320k	N/A	0.9968 ████████	0.9952 ████████

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
48k_stereo_24k	0.8566 ███████░	0.8392 ███████░
48k_stereo_32k	0.8573 ███████░	0.8396 ███████░
48k_stereo_40k	0.8575 ███████░	0.8410 ███████░
48k_stereo_48k	0.8573 ███████░	0.8411 ███████░
48k_stereo_56k	N/A	0.8411 ███████░
48k_stereo_64k	N/A	0.8411 ███████░
48k_stereo_96k	N/A	0.8412 ███████░
48k_stereo_128k	N/A	0.8412 ███████░
48k_stereo_160k	N/A	0.8412 ███████░
48k_stereo_192k	N/A	0.8412 ███████░
48k_stereo_256k	N/A	0.8412 ███████░
48k_stereo_320k	N/A	0.8412 ███████░

Transient Fidelity (48 kHz Stereo)

Note: Measured as 1 / (1 + mean |attack-centroid-shift| ms) across onsets. Higher is truer (attack timing closer to reference).

xychart-beta
    title "Transient Fidelity across Bitrates - 48 kHz Stereo (Higher is Better)"
    x-axis ["24k", "32k", "40k", "48k", "56k", "64k", "96k", "128k", "160k", "192k", "256k", "320k"]
    y-axis "Transient Fidelity" 0.703 --> 1
    line "FAAC 2.2.0" [0.7987, 0.8526, 0.8840, 0.9043, 0.9235, 0.9312, 0.9533, 0.9732, 0.9804, 0.9836, 0.9889, 0.9921]
    line "fdkaac 1.0.9" [0.8176, 0.8616, 0.8905, 0.9030, 0.9164, 0.9292, 0.9532, 0.9679, 0.9735, 0.9780, 0.9822, 0.9845]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [0.7407, 0.7294, 0.8131, 0.8159, 0.8828, 0.9082, 0.9561, 0.9715, 0.9788, 0.9850, 0.9900, 0.9934]
    line "Apple AAC 27.0" [0.8177, 0.8458, 0.8620, 0.8805, 0.8841, 0.9053, 0.9253, 0.9570, 0.9684, 0.9806, 0.9870, 0.9916]

View Detailed Transient Fidelity Table (48 kHz Stereo)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
48k_stereo_24k	0.8195 ███████░	0.5789 █████░░░	0.7780 ██████░░	0.7407 ██████░░
48k_stereo_32k	0.8485 ███████░	0.7655 ██████░░	0.8205 ███████░	0.7294 ██████░░
48k_stereo_40k	0.8636 ███████░	0.8528 ███████░	0.8477 ███████░	0.8131 ███████░
48k_stereo_48k	0.8714 ███████░	0.8914 ███████░	0.8750 ███████░	0.8159 ███████░
48k_stereo_56k	0.8700 ███████░	0.9072 ███████░	0.8805 ███████░	0.8828 ███████░
48k_stereo_64k	0.8864 ███████░	0.9242 ███████░	0.9055 ███████░	0.9082 ███████░
48k_stereo_96k	0.9253 ███████░	0.9533 ████████	0.9505 ████████	0.9561 ████████
48k_stereo_128k	0.9570 ████████	0.9732 ████████	0.9679 ████████	0.9715 ████████
48k_stereo_160k	0.9684 ████████	0.9804 ████████	0.9735 ████████	0.9788 ████████
48k_stereo_192k	0.9806 ████████	0.9836 ████████	0.9780 ████████	0.9850 ████████
48k_stereo_256k	0.9870 ████████	0.9889 ████████	0.9822 ████████	0.9900 ████████
48k_stereo_320k	0.9916 ████████	0.9921 ████████	0.9845 ████████	0.9934 ████████

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
48k_stereo_24k	0.8279 ███████░	0.7987 ██████░░	0.8176 ███████░
48k_stereo_32k	0.8458 ███████░	0.8526 ███████░	0.8616 ███████░
48k_stereo_40k	0.8620 ███████░	0.8840 ███████░	0.8905 ███████░
48k_stereo_48k	0.8805 ███████░	0.9043 ███████░	0.9030 ███████░
48k_stereo_56k	0.8841 ███████░	0.9235 ███████░	0.9164 ███████░
48k_stereo_64k	0.9053 ███████░	0.9312 ███████░	0.9292 ███████░
48k_stereo_96k	N/A	0.9488 ████████	0.9532 ████████
48k_stereo_128k	N/A	0.9658 ████████	0.9619 ████████
48k_stereo_160k	N/A	0.9721 ████████	0.9646 ████████
48k_stereo_192k	N/A	0.9752 ████████	0.9670 ████████
48k_stereo_256k	N/A	0.9789 ████████	0.9676 ████████
48k_stereo_320k	N/A	0.9790 ████████	0.9712 ████████

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
48k_stereo_24k	0.8177 ███████░	0.8469 ███████░
48k_stereo_32k	0.8407 ███████░	0.8663 ███████░
48k_stereo_40k	0.8705 ███████░	0.8767 ███████░
48k_stereo_48k	0.8844 ███████░	0.8832 ███████░
48k_stereo_56k	N/A	0.8875 ███████░
48k_stereo_64k	N/A	0.8893 ███████░
48k_stereo_96k	N/A	0.8924 ███████░
48k_stereo_128k	N/A	0.8926 ███████░
48k_stereo_160k	N/A	0.8935 ███████░
48k_stereo_192k	N/A	0.8935 ███████░
48k_stereo_256k	N/A	0.8935 ███████░
48k_stereo_320k	N/A	0.8935 ███████░

Encoding Speed (48 kHz Stereo)

Note: Encoding throughput measured in xRealtime. Higher is Better.

xychart-beta
    title "Encoding Speed across Bitrates - 48 kHz Stereo (Higher is Better)"
    x-axis ["24k", "32k", "40k", "48k", "56k", "64k", "96k", "128k", "160k", "192k", "256k", "320k"]
    y-axis "Speed (xRT)" 0 --> 100
    line "FAAC 2.2.0" [556.4206, 496.2043, 447.3488, 461.9080, 450.1110, 463.5571, 452.1696, 450.7135, 436.2091, 421.4500, 420.1831, 412.7508]
    line "fdkaac 1.0.9" [105.5134, 98.3042, 87.8397, 86.6946, 85.1273, 80.8475, 79.8988, 101.4018, 97.7557, 91.9415, 87.8466, 86.9848]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [38.2334, 41.8192, 42.4630, 34.2619, 34.1417, 33.8743, 28.1730, 26.3011, 25.6980, 25.7443, 24.3340, 23.3411]
    line "Apple AAC 27.0" [132.7693, 118.6260, 102.2218, 99.1033, 98.8741, 101.3922, 95.6270, 94.0303, 93.8463, 89.1232, 86.4465, 87.1568]

Bitrate Accuracy (48 kHz Stereo)

Note: Deviation from target bitrate calculated from pure elementary stream audio bytes. Lower is Better.

xychart-beta
    title "Bitrate Accuracy across Bitrates - 48 kHz Stereo (Lower is Better)"
    x-axis ["24k", "32k", "40k", "48k", "56k", "64k", "96k", "128k", "160k", "192k", "256k", "320k"]
    y-axis "Bitrate Error (%)" 0 --> 20
    line "FAAC 2.2.0" [0.8801, 0.9141, 1.0476, 0.9866, 0.7708, 0.5918, 0.6982, 0.7640, 0.7694, 0.7549, 0.7839, 0.9755]
    line "fdkaac 1.0.9" [4.8780, 3.3031, 2.5186, 2.0334, 1.8047, 1.6546, 1.4416, 0.7833, 0.6782, 0.6109, 0.5375, 0.5299]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [47.6914, 11.4666, 1.0217, 1.3205, 1.0591, 0.9347, 0.9423, 0.8166, 0.7169, 0.7384, 0.6176, 0.6718]
    line "Apple AAC 27.0" [5.1999, 3.0197, 3.3766, 3.0904, 3.7109, 4.5492, 2.0993, 2.2681, 2.7256, 3.0356, 2.2989, 2.4241]

View Detailed Bitrate Accuracy Table (48 kHz Stereo)

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
48k_stereo_24k	4.7%	6.0%	5.6%	47.7%
48k_stereo_32k	4.3%	1.5%	4.0%	11.5%
48k_stereo_40k	3.6%	1.0%	2.6%	1.0%
48k_stereo_48k	2.1%	0.9%	1.9%	1.3%
48k_stereo_56k	2.4%	0.8%	2.0%	1.1%
48k_stereo_64k	2.2%	0.7%	1.7%	0.9%
48k_stereo_96k	2.1%	0.7%	1.1%	0.9%
48k_stereo_128k	2.3%	0.8%	0.8%	0.8%
48k_stereo_160k	2.7%	0.8%	0.7%	0.7%
48k_stereo_192k	3.0%	0.8%	0.6%	0.7%
48k_stereo_256k	2.3%	0.8%	0.5%	0.6%
48k_stereo_320k	2.4%	1.0%	0.5%	0.7%

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
48k_stereo_24k	6.2%	0.9%	4.9%
48k_stereo_32k	3.0%	0.9%	3.3%
48k_stereo_40k	3.4%	1.0%	2.5%
48k_stereo_48k	3.1%	1.0%	2.0%
48k_stereo_56k	3.7%	0.8%	1.8%
48k_stereo_64k	4.5%	0.6%	1.7%
48k_stereo_96k	N/A	0.4%	1.4%
48k_stereo_128k	N/A	0.5%	1.3%
48k_stereo_160k	N/A	0.5%	1.2%
48k_stereo_192k	N/A	0.6%	1.2%
48k_stereo_256k	N/A	3.8%	1.2%
48k_stereo_320k	N/A	20.4%	8.9%

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
48k_stereo_24k	5.2%	2.7%
48k_stereo_32k	8.4%	2.2%
48k_stereo_40k	6.1%	2.1%
48k_stereo_48k	5.6%	1.9%
48k_stereo_56k	N/A	1.8%
48k_stereo_64k	N/A	1.8%
48k_stereo_96k	N/A	1.7%
48k_stereo_128k	N/A	1.7%
48k_stereo_160k	N/A	8.5%
48k_stereo_192k	N/A	23.7%
48k_stereo_256k	N/A	42.8%
48k_stereo_320k	N/A	54.2%

44.1 kHz 5.1 Surround Quality Across Bitrates

View Detailed 44.1 kHz 5.1 Surround Average & Worst MOS Tables

Per-Scenario Average MOS (44.1 kHz 5.1 Surround)

Per-Scenario 1st Percentile MOS ($P_1$) (44.1 kHz 5.1 Surround)

Note: 1st percentile MOS ($P_1$) score threshold observed across clips in the scenario. Highlights edge-case clip degradation. A 🐛 names the clip when every other encoder scored ≥0.75 MOS higher on that exact clip -- likely a defect specific to this encoder; see Quality Outliers under Issues Worth Investigating below.

Stereo Image Fidelity (44.1 kHz 5.1 Surround)

Note: Measured as 1.0 - |Coherence(Ref) - Coherence(Deg)|. Higher is truer (closer to reference stereo image).

View Detailed Stereo Fidelity Table (44.1 kHz 5.1 Surround)

Transient Fidelity (44.1 kHz 5.1 Surround)

Note: Measured as 1 / (1 + mean |attack-centroid-shift| ms) across onsets. Higher is truer (attack timing closer to reference).

View Detailed Transient Fidelity Table (44.1 kHz 5.1 Surround)

Encoding Speed (44.1 kHz 5.1 Surround)

Note: Encoding throughput measured in xRealtime. Higher is Better.

Bitrate Accuracy (44.1 kHz 5.1 Surround)

Note: Deviation from target bitrate calculated from pure elementary stream audio bytes. Lower is Better.

View Detailed Bitrate Accuracy Table (44.1 kHz 5.1 Surround)

BD-Rate Relative Efficiency (vs FAAC 2.2.0 (6acbe23a))

Note: Bjontegaard-delta rate (BD-rate) measures the average percentage difference in bitrate for equal perceptual quality (MOS). Negative % = candidate is more efficient (uses fewer bits for same quality). BD-rate holds quality fixed by construction, avoiding bitrate-bias traps of raw fixed-rate MOS deltas.

Encoder	Profile	BD-Rate % vs Baseline
Apple AAC 27.0	LC	+36.30%
fdkaac 1.0.9	LC	+18.94%
FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)	LC	+14.46%

Encoder Efficiency & Footprint

Encoding Speed (xRT)

xychart-beta
    title "Encoding Speed across Scenarios (xRealtime, Higher is Better)"
    x-axis ["20k", "24k", "voip_24k", "28k", "32k", "16k", "48k", "64k", "80k", "96k", "64k", "128k", "160k", "192k", "256k", "24k", "32k", "40k", "48k", "56k", "64k", "96k", "128k", "160k", "192k", "256k", "320k", "96k", "160k", "224k", "256k", "384k", "448k"]
    y-axis "Speed (xRT)" 0 --> 715.8
    line "FAAC 2.2.0" [639.0591, 591.3193, 644.4214, 652.8743, 638.8968, 600.7091, 583.5982, 528.4411, 557.0522, 544.0627, 481.1670, 473.9142, 437.5758, 418.8853, 424.4584, 556.4206, 496.2043, 447.3488, 461.9080, 450.1110, 463.5571, 452.1696, 450.7135, 436.2091, 421.4500, 420.1831, 412.7508, 412.7508, 412.7508, 412.7508, 412.7508, 412.7508, 412.7508]
    line "fdkaac 1.0.9" [394.7191, 404.9186, 381.9877, 367.9668, 358.3244, 190.4136, 113.4672, 113.8784, 120.8199, 117.7563, 88.9688, 103.9320, 94.9915, 96.3698, 90.0045, 105.5134, 98.3042, 87.8397, 86.6946, 85.1273, 80.8475, 79.8988, 101.4018, 97.7557, 91.9415, 87.8466, 86.9848, 86.9848, 86.9848, 86.9848, 86.9848, 86.9848, 86.9848]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [77.9885, 80.4293, 78.7161, 73.4564, 71.7775, 40.9346, 38.3646, 37.8319, 35.6218, 34.2138, 34.8688, 27.3080, 25.9953, 27.8717, 27.2397, 38.2334, 41.8192, 42.4630, 34.2619, 34.1417, 33.8743, 28.1730, 26.3011, 25.6980, 25.7443, 24.3340, 23.3411, 23.3411, 23.3411, 23.3411, 23.3411, 23.3411, 23.3411]
    line "Apple AAC 27.0" [142.0263, 145.9709, 147.2673, 141.4343, 140.7851, 171.1924, 118.1539, 121.5872, 112.2117, 110.3071, 106.2185, 91.2387, 94.4879, 93.3297, 90.6960, 132.7693, 118.6260, 102.2218, 99.1033, 98.8741, 101.3922, 95.6270, 94.0303, 93.8463, 89.1232, 86.4465, 87.1568, 87.1568, 87.1568, 87.1568, 87.1568, 87.1568, 87.1568]

Codec ROM (Flash) Size

xychart-beta
    title "Codec Code + Read-Only Data Size (KB, Lower is Better)"
    x-axis ["FAAC 2.2.0 (6acbe23a)", "fdkaac 1.0.9", "FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)", "Apple AAC 27.0"]
    y-axis "ROM Size (KB)" 0 --> 1176
    bar "ROM Size" [73.4, 940.5, 274.5, 100.3]

View Detailed Per-Scenario Efficiency Table

LC Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9	FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)
16k_mono_20k	142.0x ██░░░░░░	639.1x ████████	394.7x █████░░░	78.0x █░░░░░░░
16k_mono_24k	146.0x ██░░░░░░	591.3x ███████░	404.9x █████░░░	80.4x █░░░░░░░
16k_mono_voip_24k	147.3x ██░░░░░░	644.4x ████████	382.0x █████░░░	78.7x █░░░░░░░
24k_mono_28k	141.4x ██░░░░░░	652.9x ████████	368.0x █████░░░	73.5x █░░░░░░░
24k_mono_32k	140.8x ██░░░░░░	638.9x ████████	358.3x ████░░░░	71.8x █░░░░░░░
32k_stereo_16k	171.2x ██░░░░░░	637.0x ████████	228.9x ███░░░░░	40.9x █░░░░░░░
32k_stereo_48k	119.7x █░░░░░░░	583.6x ███████░	153.3x ██░░░░░░	38.4x ░░░░░░░░
32k_stereo_64k	115.9x █░░░░░░░	528.4x ██████░░	134.2x ██░░░░░░	37.8x ░░░░░░░░
32k_stereo_80k	112.2x █░░░░░░░	557.1x ███████░	120.8x █░░░░░░░	35.6x ░░░░░░░░
32k_stereo_96k	110.3x █░░░░░░░	544.1x ███████░	117.8x █░░░░░░░	34.2x ░░░░░░░░
44k1_stereo_64k	110.0x █░░░░░░░	484.0x ██████░░	120.0x █░░░░░░░	34.9x ░░░░░░░░
44k1_stereo_128k	91.2x █░░░░░░░	473.9x ██████░░	103.9x █░░░░░░░	27.3x ░░░░░░░░
44k1_stereo_160k	94.5x █░░░░░░░	437.6x █████░░░	95.0x █░░░░░░░	26.0x ░░░░░░░░
44k1_stereo_192k	93.3x █░░░░░░░	418.9x █████░░░	96.4x █░░░░░░░	27.9x ░░░░░░░░
44k1_stereo_256k	90.7x █░░░░░░░	424.5x █████░░░	90.0x █░░░░░░░	27.2x ░░░░░░░░
48k_stereo_24k	177.6x ██░░░░░░	537.3x ███████░	166.2x ██░░░░░░	38.2x ░░░░░░░░
48k_stereo_32k	158.2x ██░░░░░░	476.1x ██████░░	161.1x ██░░░░░░	41.8x █░░░░░░░
48k_stereo_40k	137.9x ██░░░░░░	448.7x █████░░░	130.5x ██░░░░░░	42.5x █░░░░░░░
48k_stereo_48k	119.7x █░░░░░░░	462.3x ██████░░	133.8x ██░░░░░░	34.3x ░░░░░░░░
48k_stereo_56k	106.7x █░░░░░░░	491.9x ██████░░	116.6x █░░░░░░░	34.1x ░░░░░░░░
48k_stereo_64k	105.6x █░░░░░░░	465.7x ██████░░	110.1x █░░░░░░░	33.9x ░░░░░░░░
48k_stereo_96k	95.6x █░░░░░░░	452.2x ██████░░	102.3x █░░░░░░░	28.2x ░░░░░░░░
48k_stereo_128k	94.0x █░░░░░░░	450.7x ██████░░	101.4x █░░░░░░░	26.3x ░░░░░░░░
48k_stereo_160k	93.8x █░░░░░░░	436.2x █████░░░	97.8x █░░░░░░░	25.7x ░░░░░░░░
48k_stereo_192k	89.1x █░░░░░░░	421.4x █████░░░	91.9x █░░░░░░░	25.7x ░░░░░░░░
48k_stereo_256k	86.4x █░░░░░░░	420.2x █████░░░	87.8x █░░░░░░░	24.3x ░░░░░░░░
48k_stereo_320k	87.2x █░░░░░░░	412.8x █████░░░	87.0x █░░░░░░░	23.3x ░░░░░░░░
44k1_51_96k	N/A	N/A	N/A	N/A
44k1_51_160k	N/A	N/A	N/A	N/A
44k1_51_224k	N/A	N/A	N/A	N/A
44k1_51_256k	N/A	N/A	N/A	N/A
44k1_51_384k	N/A	N/A	N/A	N/A
44k1_51_448k	N/A	N/A	N/A	N/A

HE-v1 Profile

Scenario	Apple AAC 27.0	FAAC 2.2.0 (6acbe23a)	fdkaac 1.0.9
16k_mono_20k	N/A	N/A	N/A
16k_mono_24k	N/A	N/A	N/A
16k_mono_voip_24k	N/A	N/A	N/A
24k_mono_28k	N/A	N/A	N/A
24k_mono_32k	N/A	N/A	N/A
32k_stereo_16k	N/A	600.7x ████████	144.5x ██░░░░░░
32k_stereo_48k	118.2x ██░░░░░░	569.9x ████████	113.5x ██░░░░░░
32k_stereo_64k	121.6x ██░░░░░░	542.9x ███████░	113.9x ██░░░░░░
32k_stereo_80k	N/A	559.7x ███████░	116.6x ██░░░░░░
32k_stereo_96k	N/A	558.2x ███████░	111.8x █░░░░░░░
44k1_stereo_64k	106.2x █░░░░░░░	481.2x ██████░░	89.0x █░░░░░░░
44k1_stereo_128k	N/A	458.2x ██████░░	85.2x █░░░░░░░
44k1_stereo_160k	N/A	453.6x ██████░░	83.1x █░░░░░░░
44k1_stereo_192k	N/A	463.4x ██████░░	81.3x █░░░░░░░
44k1_stereo_256k	N/A	422.5x ██████░░	81.3x █░░░░░░░
48k_stereo_24k	143.3x ██░░░░░░	556.4x ███████░	105.5x █░░░░░░░
48k_stereo_32k	118.6x ██░░░░░░	496.2x ███████░	98.3x █░░░░░░░
48k_stereo_40k	102.2x █░░░░░░░	447.3x ██████░░	87.8x █░░░░░░░
48k_stereo_48k	99.1x █░░░░░░░	461.9x ██████░░	86.7x █░░░░░░░
48k_stereo_56k	98.9x █░░░░░░░	450.1x ██████░░	85.1x █░░░░░░░
48k_stereo_64k	101.4x █░░░░░░░	463.6x ██████░░	80.8x █░░░░░░░
48k_stereo_96k	N/A	429.8x ██████░░	79.9x █░░░░░░░
48k_stereo_128k	N/A	416.1x ██████░░	80.9x █░░░░░░░
48k_stereo_160k	N/A	447.0x ██████░░	79.6x █░░░░░░░
48k_stereo_192k	N/A	425.4x ██████░░	77.7x █░░░░░░░
48k_stereo_256k	N/A	394.8x █████░░░	74.4x █░░░░░░░
48k_stereo_320k	N/A	397.2x █████░░░	76.6x █░░░░░░░
44k1_51_96k	N/A	N/A	N/A
44k1_51_160k	N/A	N/A	N/A
44k1_51_224k	N/A	N/A	N/A
44k1_51_256k	N/A	N/A	N/A
44k1_51_384k	N/A	N/A	N/A
44k1_51_448k	N/A	N/A	N/A

HE-v2 Profile

Scenario	Apple AAC 27.0	fdkaac 1.0.9
16k_mono_20k	N/A	N/A
16k_mono_24k	N/A	N/A
16k_mono_voip_24k	N/A	N/A
24k_mono_28k	N/A	N/A
24k_mono_32k	N/A	N/A
32k_stereo_16k	N/A	190.4x ████████
32k_stereo_48k	139.8x ██████░░	166.2x ███████░
32k_stereo_64k	N/A	162.1x ███████░
32k_stereo_80k	N/A	159.0x ███████░
32k_stereo_96k	N/A	159.0x ███████░
44k1_stereo_64k	N/A	130.4x █████░░░
44k1_stereo_128k	N/A	117.5x █████░░░
44k1_stereo_160k	N/A	119.8x █████░░░
44k1_stereo_192k	N/A	118.3x █████░░░
44k1_stereo_256k	N/A	119.7x █████░░░
48k_stereo_24k	132.8x ██████░░	136.2x ██████░░
48k_stereo_32k	122.4x █████░░░	133.4x ██████░░
48k_stereo_40k	116.2x █████░░░	123.6x █████░░░
48k_stereo_48k	115.6x █████░░░	121.6x █████░░░
48k_stereo_56k	N/A	122.9x █████░░░
48k_stereo_64k	N/A	117.9x █████░░░
48k_stereo_96k	N/A	115.5x █████░░░
48k_stereo_128k	N/A	118.4x █████░░░
48k_stereo_160k	N/A	114.3x █████░░░
48k_stereo_192k	N/A	115.5x █████░░░
48k_stereo_256k	N/A	117.3x █████░░░
48k_stereo_320k	N/A	116.6x █████░░░
44k1_51_96k	N/A	N/A
44k1_51_160k	N/A	N/A
44k1_51_224k	N/A	N/A
44k1_51_256k	N/A	N/A
44k1_51_384k	N/A	N/A
44k1_51_448k	N/A	N/A

🐛 View Quality Outliers (Issues Worth Investigating)

Quality Outliers (Issues Worth Investigating)

Note: Flags clips where this encoder scored ≥0.75 MOS lower than the average of all other encoders on the exact same clip. These clips represent isolated codec defects, killer clips, or tuning bugs.

Encoder	Profile	Scenario	Outlier Clip	Encoder MOS	Peer Avg MOS	Defect Gap
fdkaac 1.0.9	HE-v2	44k1_stereo_256k	`mof.wav`	1.75	4.87	-3.11 MOS
fdkaac 1.0.9	HE-v2	48k_stereo_320k	`mof.wav`	1.79	4.91	-3.11 MOS
fdkaac 1.0.9	HE-v2	48k_stereo_256k	`mof.wav`	1.79	4.90	-3.10 MOS
fdkaac 1.0.9	HE-v2	44k1_stereo_192k	`mof.wav`	1.75	4.84	-3.09 MOS
fdkaac 1.0.9	HE-v2	48k_stereo_192k	`mof.wav`	1.79	4.87	-3.08 MOS
fdkaac 1.0.9	HE-v2	44k1_stereo_160k	`mof.wav`	1.75	4.81	-3.05 MOS
fdkaac 1.0.9	HE-v2	48k_stereo_160k	`mof.wav`	1.79	4.83	-3.04 MOS
fdkaac 1.0.9	HE-v2	44k1_stereo_128k	`mof.wav`	1.75	4.74	-2.99 MOS
fdkaac 1.0.9	HE-v2	48k_stereo_128k	`mof.wav`	1.79	4.77	-2.98 MOS
fdkaac 1.0.9	HE-v2	48k_stereo_96k	`mof.wav`	1.79	4.59	-2.80 MOS
fdkaac 1.0.9	HE-v2	32k_stereo_96k	`mof.wav`	1.72	4.44	-2.73 MOS
fdkaac 1.0.9	HE-v2	32k_stereo_80k	`mof.wav`	1.72	4.33	-2.61 MOS
fdkaac 1.0.9	HE-v2	44k1_stereo_64k	`mof.wav`	1.76	4.13	-2.37 MOS
fdkaac 1.0.9	HE-v2	48k_stereo_64k	`mof.wav`	1.80	4.14	-2.34 MOS
fdkaac 1.0.9	HE-v2	32k_stereo_64k	`mof.wav`	1.72	4.06	-2.34 MOS
fdkaac 1.0.9	HE-v2	48k_stereo_56k	`mof.wav`	1.79	3.92	-2.13 MOS
Apple AAC 27.0	LC	48k_stereo_24k	`girl.16b48k.wav`	1.01	2.97	-1.96 MOS
fdkaac 1.0.9	HE-v2	32k_stereo_48k	`mof.wav`	1.73	3.24	-1.51 MOS
Apple AAC 27.0	LC	48k_stereo_32k	`Last_Of_The_Mohicanz__Sample_.16b48k.wav`	1.81	3.32	-1.51 MOS
Apple AAC 27.0	LC	48k_stereo_40k	`Last_Of_The_Mohicanz__Sample_.16b48k.wav`	2.17	3.65	-1.48 MOS
Apple AAC 27.0	LC	48k_stereo_48k	`9-Have-big-expensive-car.441.16b48k.wav`	2.31	3.79	-1.48 MOS
fdkaac 1.0.9	HE-v2	48k_stereo_48k	`mof.wav`	1.79	3.25	-1.46 MOS
Apple AAC 27.0	LC	32k_stereo_16k	`girl.16b48k.wav`	1.01	2.46	-1.45 MOS
Apple AAC 27.0	LC	32k_stereo_48k	`9-Have-big-expensive-car.441.16b48k.wav`	2.32	3.71	-1.39 MOS
fdkaac 1.0.9	LC	48k_stereo_32k	`Last_Of_The_Mohicanz__Sample_.16b48k.wav`	2.03	3.29	-1.26 MOS
Apple AAC 27.0	HE-v2	32k_stereo_48k	`mof.wav`	1.97	3.21	-1.24 MOS
Apple AAC 27.0	HE-v2	48k_stereo_48k	`mof.wav`	2.05	3.22	-1.17 MOS
fdkaac 1.0.9	HE-v2	48k_stereo_40k	`mof.wav`	1.80	2.94	-1.15 MOS
fdkaac 1.0.9	LC	48k_stereo_48k	`velvet.16b48k.wav`	2.32	3.47	-1.14 MOS
FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)	LC	48k_stereo_32k	`velvet.16b48k.wav`	1.87	3.01	-1.14 MOS
fdkaac 1.0.9	LC	48k_stereo_40k	`velvet.16b48k.wav`	2.10	3.21	-1.11 MOS
FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)	LC	16k_mono_voip_24k	`C_24_NOISE_FG.wav`	2.56	3.61	-1.05 MOS
Apple AAC 27.0	LC	48k_stereo_56k	`velvet.16b48k.wav`	2.77	3.81	-1.04 MOS
Apple AAC 27.0	LC	44k1_stereo_64k	`9-Have-big-expensive-car.441.16b48k.wav`	3.42	4.31	-0.90 MOS
fdkaac 1.0.9	LC	32k_stereo_48k	`velvet.16b48k.wav`	2.52	3.41	-0.89 MOS
fdkaac 1.0.9	HE-v2	48k_stereo_32k	`mof.wav`	1.76	2.64	-0.88 MOS
fdkaac 1.0.9	LC	48k_stereo_24k	`The Chastising of Renegade.16b48k.wav`	1.67	2.55	-0.88 MOS
Apple AAC 27.0	HE-v2	48k_stereo_40k	`mof.wav`	2.04	2.91	-0.87 MOS
FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)	LC	48k_stereo_40k	`mof.wav`	2.05	2.91	-0.86 MOS
FAAC 2.2.0 (6acbe23a)	LC	48k_stereo_40k	`12-German-male-speech.441.16b48k.wav`	2.77	3.62	-0.86 MOS
FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)	LC	32k_stereo_80k	`girl.16b48k.wav`	3.28	4.14	-0.85 MOS
Apple AAC 27.0	HE-v1	48k_stereo_24k	`12-German-male-speech.441.16b48k.wav`	1.84	2.69	-0.85 MOS
FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)	LC	32k_stereo_64k	`girl.16b48k.wav`	3.12	3.94	-0.82 MOS
Apple AAC 27.0	LC	48k_stereo_64k	`9-Have-big-expensive-car.441.16b48k.wav`	3.51	4.32	-0.81 MOS
FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)	LC	48k_stereo_96k	`girl.16b48k.wav`	3.71	4.50	-0.79 MOS
FFmpeg AAC N-126786-g3fc4f99a79 (NMR experimental)	LC	48k_stereo_56k	`girl.16b48k.wav`	3.24	3.99	-0.75 MOS

Metric Legend:

Ranking: by 1st Percentile MOS ($P_1$), then Overall MOS as tiebreaker.
1st Percentile MOS ($P_1$): Score threshold that 99% of tested clips equal or exceed (Higher is Better)
Quality (MOS): Perceptual audio quality (1-5, Higher is Better)
Stereo Fidelity: Faithfulness of stereo image (0-1, Higher is Better)
Transient Fidelity: How little attacks are smeared/delayed (0-1, Higher is Better)
Speed: Encoding throughput (Higher is Better)
Bitrate Error: Deviation from target bitrate (Lower is Better)
ROM (Flash): Codec code + read-only + initialized data size (.text + .rodata + .data, Lower is Better)

🔊 Decoder Leaderboard

Objective evaluation of AAC decoders on Spec Conformance (SNR), Decoded Quality (MOS), Stereo Fidelity, Timing Alignment Error, Speed, and Footprint.

Overall Decoder Rankings

Rank	Decoder	Status	1st Percentile MOS	Overall MOS	Stereo Fidelity	Mean SNR	Timing Error	Speed (xRT)	Peak RAM	ROM (Flash)
🥇 1	Helix AAC 1.0	⚠️ (491x crash, 169x timeout, No HE-v2 PS (1ch))	1.880	4.206	0.8936	18.1 dB	78.40 ms	426.1x	1.9 MB	121.4 KB
🥈 2	FDK AAC 2.0.0	⚠️ (3639x crash)	1.878	4.190	0.9573	18.0 dB	0.01 ms	344.1x	4.2 MB	940.5 KB
🥉 3	FFmpeg AAC N-126786-g3fc4f99a79	⚠️ (3641x crash)	1.877	4.195	0.9564	18.1 dB	9.14 ms	135.1x	16.8 MB	274.5 KB
4	Apple AAC 27.0	⚠️ (3641x crash)	1.874	4.195	0.9572	18.1 dB	0.01 ms	174.4x	8.3 MB	100.3 KB
5	FAAD 3 (f9fbcb76)	⚠️ (3639x crash)	1.874	4.195	0.9571	18.1 dB	0.01 ms	490.3x	2.8 MB	136.0 KB
6	FAAD 2.11.3	⚠️ (3573x crash)	1.873	4.191	0.9581	18.1 dB	0.01 ms	376.8x	2.1 MB	296.3 KB

📊 View Per-Scenario Decoder Breakdowns

Detailed Per-Scenario Decoder Breakdowns

16 kHz Mono Speech

Per-Scenario Average MOS (16 kHz Mono Speech)

xychart-beta
    title "Decoder Perceptual Quality across Bitrates - 16 kHz Mono Speech (Average MOS)"
    x-axis ["20k", "24k", "voip_24k"]
    y-axis "MOS Score" 3.761 --> 4.018
    line "Helix AAC 1.0" [3.8417, 3.9370, 3.9126]
    line "FDK AAC 2.0.0" [3.8417, 3.9369, 3.9128]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [3.8411, 3.9377, 3.9124]
    line "Apple AAC 27.0" [3.8418, 3.9371, 3.9131]
    line "FAAD 3 (f9fbcb76)" [3.8405, 3.9367, 3.9117]
    line "FAAD 2.11.3" [3.8418, 3.9363, 3.9112]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
16k_mono_20k	3.842 ██████░░	3.842 ██████░░	3.841 ██████░░	3.842 ██████░░	3.841 ██████░░	3.842 ██████░░
16k_mono_24k	3.937 ██████░░	3.937 ██████░░	3.938 ██████░░	3.937 ██████░░	3.937 ██████░░	3.936 ██████░░
16k_mono_voip_24k	3.913 ██████░░	3.913 ██████░░	3.912 ██████░░	3.913 ██████░░	3.912 ██████░░	3.911 ██████░░

Spec Conformance (Mean SNR - 16 kHz Mono Speech)

xychart-beta
    title "Decoder Spec Conformance across Bitrates - 16 kHz Mono Speech (Mean SNR dB)"
    x-axis ["20k", "24k", "voip_24k"]
    y-axis "SNR (dB)" 16.09 --> 20.72
    line "Helix AAC 1.0" [17.2908, 19.5182, 18.6263]
    line "FDK AAC 2.0.0" [17.2907, 19.5182, 18.6267]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [17.2902, 19.5202, 18.6288]
    line "Apple AAC 27.0" [17.2908, 19.5182, 18.6267]
    line "FAAD 3 (f9fbcb76)" [17.2881, 19.5172, 18.6258]
    line "FAAD 2.11.3" [17.2875, 19.5116, 18.6266]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
16k_mono_20k	17.3 dB ███████░	17.3 dB ███████░	17.3 dB ███████░	17.3 dB ███████░	17.3 dB ███████░	17.3 dB ███████░
16k_mono_24k	19.5 dB ████████	19.5 dB ████████	19.5 dB ████████	19.5 dB ████████	19.5 dB ████████	19.5 dB ████████
16k_mono_voip_24k	18.6 dB ████████	18.6 dB ████████	18.6 dB ████████	18.6 dB ████████	18.6 dB ████████	18.6 dB ████████

Timing Alignment Delay (ms - 16 kHz Mono Speech)

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
16k_mono_20k	97.00 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
16k_mono_24k	97.00 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
16k_mono_voip_24k	97.00 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████

Decoding Speed (xRT - 16 kHz Mono Speech)

xychart-beta
    title "Decoding Speed across Bitrates - 16 kHz Mono Speech (xRealtime)"
    x-axis ["20k", "24k", "voip_24k"]
    y-axis "Speed (xRT)" 88.1 --> 200
    line "Helix AAC 1.0" [702.6085, 652.4048, 636.4197]
    line "FDK AAC 2.0.0" [537.4625, 516.3739, 536.7726]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [143.9609, 144.5204, 147.7135]
    line "Apple AAC 27.0" [149.8646, 153.1644, 159.4462]
    line "FAAD 3 (f9fbcb76)" [620.3534, 616.3694, 612.2554]
    line "FAAD 2.11.3" [538.8477, 504.1453, 482.6856]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
16k_mono_20k	702.6x ████████	537.5x ██████░░	144.0x ██░░░░░░	149.9x ██░░░░░░	620.4x ███████░	538.8x ██████░░
16k_mono_24k	652.4x ███████░	516.4x ██████░░	144.5x ██░░░░░░	153.2x ██░░░░░░	616.4x ███████░	504.1x ██████░░
16k_mono_voip_24k	636.4x ███████░	536.8x ██████░░	147.7x ██░░░░░░	159.4x ██░░░░░░	612.3x ███████░	482.7x █████░░░

24 kHz Mono Speech

Per-Scenario Average MOS (24 kHz Mono Speech)

xychart-beta
    title "Decoder Perceptual Quality across Bitrates - 24 kHz Mono Speech (Average MOS)"
    x-axis ["28k", "32k"]
    y-axis "MOS Score" 4.348 --> 4.595
    line "Helix AAC 1.0" [4.4277, 4.5120]
    line "FDK AAC 2.0.0" [4.4307, 4.5145]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [4.4286, 4.5139]
    line "Apple AAC 27.0" [4.4307, 4.5146]
    line "FAAD 3 (f9fbcb76)" [4.4289, 4.5124]
    line "FAAD 2.11.3" [4.4295, 4.5127]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
24k_mono_28k	4.428 ███████░	4.431 ███████░	4.429 ███████░	4.431 ███████░	4.429 ███████░	4.430 ███████░
24k_mono_32k	4.512 ███████░	4.515 ███████░	4.514 ███████░	4.515 ███████░	4.512 ███████░	4.513 ███████░

Spec Conformance (Mean SNR - 24 kHz Mono Speech)

xychart-beta
    title "Decoder Spec Conformance across Bitrates - 24 kHz Mono Speech (Mean SNR dB)"
    x-axis ["28k", "32k"]
    y-axis "SNR (dB)" 16.11 --> 20.06
    line "Helix AAC 1.0" [17.3108, 18.8572]
    line "FDK AAC 2.0.0" [17.3106, 18.8571]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [17.3101, 18.8568]
    line "Apple AAC 27.0" [17.3107, 18.8571]
    line "FAAD 3 (f9fbcb76)" [17.3119, 18.8624]
    line "FAAD 2.11.3" [17.3159, 18.8629]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
24k_mono_28k	17.3 dB ███████░	17.3 dB ███████░	17.3 dB ███████░	17.3 dB ███████░	17.3 dB ███████░	17.3 dB ███████░
24k_mono_32k	18.9 dB ████████	18.9 dB ████████	18.9 dB ████████	18.9 dB ████████	18.9 dB ████████	18.9 dB ████████

Timing Alignment Delay (ms - 24 kHz Mono Speech)

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
24k_mono_28k	64.67 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
24k_mono_32k	64.67 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████

Decoding Speed (xRT - 24 kHz Mono Speech)

xychart-beta
    title "Decoding Speed across Bitrates - 24 kHz Mono Speech (xRealtime)"
    x-axis ["28k", "32k"]
    y-axis "Speed (xRT)" 68 --> 200
    line "Helix AAC 1.0" [744.1000, 747.2962]
    line "FDK AAC 2.0.0" [599.4081, 592.8930]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [138.3303, 129.7534]
    line "Apple AAC 27.0" [163.5405, 165.3013]
    line "FAAD 3 (f9fbcb76)" [730.8933, 698.8497]
    line "FAAD 2.11.3" [499.5335, 494.0919]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
24k_mono_28k	744.1x ████████	599.4x ██████░░	138.3x █░░░░░░░	163.5x ██░░░░░░	730.9x ████████	499.5x █████░░░
24k_mono_32k	747.3x ████████	592.9x ██████░░	129.8x █░░░░░░░	165.3x ██░░░░░░	698.8x ███████░	494.1x █████░░░

32 kHz Stereo

Per-Scenario Average MOS (32 kHz Stereo)

xychart-beta
    title "Decoder Perceptual Quality across Bitrates - 32 kHz Stereo (Average MOS)"
    x-axis ["16k", "48k", "64k", "80k", "96k"]
    y-axis "MOS Score" 2.114 --> 4.754
    line "Helix AAC 1.0" [2.3623, 3.8196, 4.2830, 4.4546, 4.5341]
    line "FDK AAC 2.0.0" [2.3336, 3.7732, 4.2502, 4.4215, 4.5000]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [2.3424, 3.7838, 4.2643, 4.4325, 4.5113]
    line "Apple AAC 27.0" [2.3430, 3.7834, 4.2648, 4.4314, 4.5115]
    line "FAAD 3 (f9fbcb76)" [2.3425, 3.7842, 4.2639, 4.4309, 4.5118]
    line "FAAD 2.11.3" [2.3418, 3.7755, 4.2608, 4.4278, 4.5068]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
32k_stereo_16k	2.035 ███░░░░░	2.035 ███░░░░░	2.034 ███░░░░░	2.035 ███░░░░░	2.034 ███░░░░░	2.035 ███░░░░░
32k_stereo_48k	3.584 ██████░░	3.584 ██████░░	3.583 ██████░░	3.583 ██████░░	3.584 ██████░░	3.584 ██████░░
32k_stereo_64k	4.321 ███████░	4.322 ███████░	4.322 ███████░	4.323 ███████░	4.321 ███████░	4.324 ███████░
32k_stereo_80k	4.622 ███████░	4.621 ███████░	4.621 ███████░	4.620 ███████░	4.618 ███████░	4.622 ███████░
32k_stereo_96k	4.734 ████████	4.733 ████████	4.732 ████████	4.733 ████████	4.733 ████████	4.733 ████████

HE-v1 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
32k_stereo_16k	2.715 ████░░░░	2.685 ████░░░░	2.717 ████░░░░	2.718 ████░░░░	2.718 ████░░░░	2.721 ████░░░░
32k_stereo_48k	4.174 ███████░	4.144 ███████░	4.177 ███████░	4.176 ███████░	4.177 ███████░	4.177 ███████░
32k_stereo_64k	4.403 ███████░	4.367 ███████░	4.404 ███████░	4.404 ███████░	4.404 ███████░	4.404 ███████░
32k_stereo_80k	4.461 ███████░	4.423 ███████░	4.462 ███████░	4.462 ███████░	4.462 ███████░	4.462 ███████░
32k_stereo_96k	4.513 ███████░	4.472 ███████░	4.513 ███████░	4.513 ███████░	4.513 ███████░	4.513 ███████░

HE-v2 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
32k_stereo_16k	2.967 (1ch) █████░░░	2.827 █████░░░	2.827 █████░░░	2.827 █████░░░	2.827 █████░░░	2.809 ████░░░░
32k_stereo_48k	3.758 (1ch) ██████░░	3.595 ██████░░	3.595 ██████░░	3.594 ██████░░	3.595 ██████░░	3.557 ██████░░
32k_stereo_64k	3.769 (1ch) ██████░░	3.615 ██████░░	3.615 ██████░░	3.615 ██████░░	3.615 ██████░░	3.581 ██████░░
32k_stereo_80k	3.774 (1ch) ██████░░	3.619 ██████░░	3.619 ██████░░	3.618 ██████░░	3.619 ██████░░	3.585 ██████░░
32k_stereo_96k	3.778 (1ch) ██████░░	3.623 ██████░░	3.623 ██████░░	3.622 ██████░░	3.623 ██████░░	3.588 ██████░░

Scores marked (1ch) indicate mono output on HE-v2 stereo bitstreams due to lack of Parametric Stereo decoding.

Spec Conformance (Mean SNR - 32 kHz Stereo)

xychart-beta
    title "Decoder Spec Conformance across Bitrates - 32 kHz Stereo (Mean SNR dB)"
    x-axis ["16k", "48k", "64k", "80k", "96k"]
    y-axis "SNR (dB)" 5.57 --> 19.66
    line "Helix AAC 1.0" [6.8528, 13.1842, 16.0365, 17.0041, 18.4593]
    line "FDK AAC 2.0.0" [6.7918, 13.0992, 15.9042, 16.8874, 18.3233]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [6.8226, 13.1822, 16.0257, 16.9893, 18.4354]
    line "Apple AAC 27.0" [6.8221, 13.1796, 16.0209, 16.9829, 18.4282]
    line "FAAD 3 (f9fbcb76)" [6.8238, 13.1785, 16.0194, 16.9819, 18.4292]
    line "FAAD 2.11.3" [6.7702, 13.0516, 15.9555, 16.9093, 18.3517]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
32k_stereo_16k	7.0 dB ███░░░░░	7.0 dB ███░░░░░	7.0 dB ███░░░░░	7.0 dB ███░░░░░	7.0 dB ███░░░░░	7.0 dB ███░░░░░
32k_stereo_48k	14.8 dB █████░░░	14.8 dB █████░░░	14.8 dB █████░░░	14.8 dB █████░░░	14.8 dB █████░░░	14.8 dB █████░░░
32k_stereo_64k	17.7 dB ███████░	17.7 dB ███████░	17.7 dB ███████░	17.7 dB ███████░	17.7 dB ███████░	17.7 dB ███████░
32k_stereo_80k	19.6 dB ███████░	19.6 dB ███████░	19.6 dB ███████░	19.6 dB ███████░	19.6 dB ███████░	19.6 dB ███████░
32k_stereo_96k	21.8 dB ████████	21.8 dB ████████	21.8 dB ████████	21.8 dB ████████	21.8 dB ████████	21.8 dB ████████

HE-v1 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
32k_stereo_16k	7.2 dB ███░░░░░	7.1 dB ███░░░░░	7.2 dB ███░░░░░	7.2 dB ███░░░░░	7.2 dB ███░░░░░	7.2 dB ███░░░░░
32k_stereo_48k	15.1 dB ███████░	14.8 dB ███████░	15.0 dB ███████░	15.0 dB ███████░	15.0 dB ███████░	15.0 dB ███████░
32k_stereo_64k	16.8 dB ████████	16.4 dB ███████░	16.8 dB ████████	16.7 dB ████████	16.7 dB ████████	16.7 dB ████████
32k_stereo_80k	16.8 dB ████████	16.4 dB ███████░	16.7 dB ████████	16.7 dB ████████	16.7 dB ████████	16.7 dB ████████
32k_stereo_96k	17.5 dB ████████	17.1 dB ████████	17.5 dB ████████	17.4 dB ████████	17.4 dB ████████	17.4 dB ████████

HE-v2 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
32k_stereo_16k	5.8 dB ██████░░	5.6 dB ██████░░	5.6 dB ██████░░	5.6 dB ██████░░	5.6 dB ██████░░	5.2 dB ██████░░
32k_stereo_48k	7.1 dB ████████	7.2 dB ████████	7.2 dB ████████	7.2 dB ████████	7.2 dB ████████	6.6 dB ███████░
32k_stereo_64k	7.0 dB ████████	7.0 dB ████████	7.0 dB ████████	7.0 dB ████████	7.0 dB ████████	6.5 dB ███████░
32k_stereo_80k	7.0 dB ████████	7.0 dB ████████	7.0 dB ████████	7.0 dB ████████	7.0 dB ████████	6.5 dB ███████░
32k_stereo_96k	7.0 dB ████████	7.0 dB ████████	7.0 dB ████████	7.0 dB ████████	7.0 dB ████████	6.5 dB ███████░

Timing Alignment Delay (ms - 32 kHz Stereo)

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
32k_stereo_16k	42.63 ms █░░░░░░░	0.15 ms ████████	0.05 ms ████████	0.14 ms ████████	0.07 ms ████████	0.18 ms ████████
32k_stereo_48k	42.67 ms █░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
32k_stereo_64k	48.50 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
32k_stereo_80k	48.50 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
32k_stereo_96k	48.50 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████

HE-v1 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
32k_stereo_16k	126.55 ms █░░░░░░░	0.02 ms ████████	30.05 ms ██████░░	0.02 ms ████████	0.02 ms ████████	0.02 ms ████████
32k_stereo_48k	138.39 ms ░░░░░░░░	0.01 ms ████████	30.05 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
32k_stereo_64k	138.39 ms ░░░░░░░░	0.01 ms ████████	30.05 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
32k_stereo_80k	126.55 ms █░░░░░░░	0.01 ms ████████	30.05 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
32k_stereo_96k	126.55 ms █░░░░░░░	0.01 ms ████████	30.05 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████

HE-v2 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
32k_stereo_16k	221.98 ms ░░░░░░░░	0.08 ms ████████	29.98 ms ███████░	0.08 ms ████████	0.08 ms ████████	0.08 ms ████████
32k_stereo_48k	192.04 ms █░░░░░░░	0.02 ms ████████	30.04 ms ███████░	0.02 ms ████████	0.02 ms ████████	0.02 ms ████████
32k_stereo_64k	222.03 ms ░░░░░░░░	0.04 ms ████████	30.03 ms ███████░	0.04 ms ████████	0.04 ms ████████	0.04 ms ████████
32k_stereo_80k	222.03 ms ░░░░░░░░	0.04 ms ████████	30.03 ms ███████░	0.04 ms ████████	0.04 ms ████████	0.04 ms ████████
32k_stereo_96k	222.03 ms ░░░░░░░░	0.04 ms ████████	30.03 ms ███████░	0.04 ms ████████	0.04 ms ████████	0.04 ms ████████

Decoding Speed (xRT - 32 kHz Stereo)

xychart-beta
    title "Decoding Speed across Bitrates - 32 kHz Stereo (xRealtime)"
    x-axis ["16k", "48k", "64k", "80k", "96k"]
    y-axis "Speed (xRT)" 94.17 --> 200
    line "Helix AAC 1.0" [563.7569, 444.1756, 434.3704, 436.3754, 434.0983]
    line "FDK AAC 2.0.0" [454.3498, 354.5864, 357.2902, 338.3488, 334.2354]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [148.2413, 140.9891, 141.8777, 147.7437, 143.8908]
    line "Apple AAC 27.0" [208.1391, 183.6245, 183.6247, 178.6178, 180.0466]
    line "FAAD 3 (f9fbcb76)" [609.1908, 531.9259, 517.5964, 542.2237, 526.4748]
    line "FAAD 2.11.3" [518.1251, 411.4624, 405.4143, 388.1731, 389.4969]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
32k_stereo_16k	722.6x ████████	557.3x ██████░░	151.5x ██░░░░░░	213.6x ██░░░░░░	709.2x ████████	590.3x ███████░
32k_stereo_48k	583.6x ██████░░	447.1x █████░░░	142.3x ██░░░░░░	192.2x ██░░░░░░	624.2x ███████░	454.8x █████░░░
32k_stereo_64k	559.8x ██████░░	428.2x █████░░░	142.4x ██░░░░░░	190.5x ██░░░░░░	597.2x ███████░	452.4x █████░░░
32k_stereo_80k	524.1x ██████░░	382.4x ████░░░░	148.0x ██░░░░░░	183.8x ██░░░░░░	595.9x ███████░	428.4x █████░░░
32k_stereo_96k	526.3x ██████░░	376.0x ████░░░░	145.1x ██░░░░░░	184.8x ██░░░░░░	587.6x ███████░	420.9x █████░░░

HE-v1 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
32k_stereo_16k	303.7x █████░░░	333.7x █████░░░	146.8x ██░░░░░░	200.4x ███░░░░░	487.3x ████████	424.0x ███████░
32k_stereo_48k	271.9x ████░░░░	294.4x █████░░░	138.9x ██░░░░░░	176.8x ███░░░░░	467.8x ████████	376.6x ██████░░
32k_stereo_64k	267.9x ████░░░░	294.0x █████░░░	140.9x ██░░░░░░	176.3x ███░░░░░	436.4x ███████░	356.7x ██████░░
32k_stereo_80k	266.1x ████░░░░	290.6x █████░░░	148.2x ██░░░░░░	170.2x ███░░░░░	477.3x ████████	331.4x █████░░░
32k_stereo_96k	258.7x ████░░░░	287.2x █████░░░	142.3x ██░░░░░░	173.9x ███░░░░░	454.4x ███████░	342.1x ██████░░

HE-v2 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
32k_stereo_16k	448.5x ████████	283.8x █████░░░	138.1x ██░░░░░░	201.7x ████░░░░	452.9x ████████	417.5x ███████░
32k_stereo_48k	423.6x ███████░	259.8x █████░░░	141.4x ██░░░░░░	176.7x ███░░░░░	443.5x ████████	377.0x ███████░
32k_stereo_64k	432.1x ████████	263.5x █████░░░	142.6x ██░░░░░░	178.1x ███░░░░░	442.7x ████████	363.6x ██████░░
32k_stereo_80k	425.8x ███████░	257.8x █████░░░	145.7x ███░░░░░	174.7x ███░░░░░	457.3x ████████	340.6x ██████░░
32k_stereo_96k	415.9x ███████░	261.5x █████░░░	142.0x ██░░░░░░	173.4x ███░░░░░	426.3x ███████░	358.5x ██████░░

44.1 kHz Stereo

Per-Scenario Average MOS (44.1 kHz Stereo)

xychart-beta
    title "Decoder Perceptual Quality across Bitrates - 44.1 kHz Stereo (Average MOS)"
    x-axis ["64k", "128k", "160k", "192k", "256k"]
    y-axis "MOS Score" 4.198 --> 4.853
    line "Helix AAC 1.0" [4.2923, 4.6772, 4.7270, 4.7546, 4.7730]
    line "FDK AAC 2.0.0" [4.2776, 4.6606, 4.7099, 4.7371, 4.7554]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [4.2814, 4.6650, 4.7148, 4.7424, 4.7607]
    line "Apple AAC 27.0" [4.2819, 4.6649, 4.7147, 4.7423, 4.7607]
    line "FAAD 3 (f9fbcb76)" [4.2822, 4.6649, 4.7147, 4.7423, 4.7607]
    line "FAAD 2.11.3" [4.2788, 4.6599, 4.7096, 4.7372, 4.7556]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
44k1_stereo_64k	4.262 ███████░	4.263 ███████░	4.261 ███████░	4.262 ███████░	4.263 ███████░	4.264 ███████░
44k1_stereo_128k	4.834 ████████	4.834 ████████	4.834 ████████	4.834 ████████	4.834 ████████	4.834 ████████
44k1_stereo_160k	4.901 ████████	4.901 ████████	4.901 ████████	4.901 ████████	4.901 ████████	4.901 ████████
44k1_stereo_192k	4.942 ████████	4.942 ████████	4.942 ████████	4.942 ████████	4.942 ████████	4.942 ████████
44k1_stereo_256k	4.970 ████████	4.970 ████████	4.970 ████████	4.970 ████████	4.970 ████████	4.970 ████████

HE-v1 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
44k1_stereo_64k	4.487 ███████░	4.475 ███████░	4.488 ███████░	4.488 ███████░	4.488 ███████░	4.488 ███████░
44k1_stereo_128k	4.777 ████████	4.762 ████████	4.777 ████████	4.777 ████████	4.777 ████████	4.777 ████████
44k1_stereo_160k	4.818 ████████	4.801 ████████	4.818 ████████	4.818 ████████	4.818 ████████	4.818 ████████
44k1_stereo_192k	4.832 ████████	4.813 ████████	4.832 ████████	4.832 ████████	4.832 ████████	4.832 ████████
44k1_stereo_256k	4.839 ████████	4.820 ████████	4.839 ████████	4.839 ████████	4.839 ████████	4.839 ████████

HE-v2 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
44k1_stereo_64k	3.827 (1ch) ██████░░	3.744 ██████░░	3.744 ██████░░	3.744 ██████░░	3.744 ██████░░	3.709 ██████░░
44k1_stereo_128k	3.852 (1ch) ██████░░	3.766 ██████░░	3.766 ██████░░	3.766 ██████░░	3.766 ██████░░	3.730 ██████░░
44k1_stereo_160k	3.852 (1ch) ██████░░	3.766 ██████░░	3.766 ██████░░	3.766 ██████░░	3.766 ██████░░	3.730 ██████░░
44k1_stereo_192k	3.852 (1ch) ██████░░	3.766 ██████░░	3.766 ██████░░	3.766 ██████░░	3.766 ██████░░	3.730 ██████░░
44k1_stereo_256k	3.852 (1ch) ██████░░	3.766 ██████░░	3.766 ██████░░	3.766 ██████░░	3.766 ██████░░	3.730 ██████░░

Scores marked (1ch) indicate mono output on HE-v2 stereo bitstreams due to lack of Parametric Stereo decoding.

Spec Conformance (Mean SNR - 44.1 kHz Stereo)

xychart-beta
    title "Decoder Spec Conformance across Bitrates - 44.1 kHz Stereo (Mean SNR dB)"
    x-axis ["64k", "128k", "160k", "192k", "256k"]
    y-axis "SNR (dB)" 14.18 --> 28.06
    line "Helix AAC 1.0" [15.3759, 21.1659, 23.1838, 24.6252, 26.8424]
    line "FDK AAC 2.0.0" [15.5071, 21.0861, 23.0780, 24.5045, 26.7090]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [15.5785, 21.1857, 23.2056, 24.6464, 26.8628]
    line "Apple AAC 27.0" [15.5775, 21.1814, 23.2009, 24.6420, 26.8588]
    line "FAAD 3 (f9fbcb76)" [15.5757, 21.1803, 23.1997, 24.6403, 26.8560]
    line "FAAD 2.11.3" [15.5134, 21.1081, 23.1289, 24.5697, 26.7863]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
44k1_stereo_64k	16.4 dB ████░░░░	16.8 dB ████░░░░	16.8 dB ████░░░░	16.8 dB ████░░░░	16.8 dB ████░░░░	16.8 dB ████░░░░
44k1_stereo_128k	24.8 dB ██████░░	24.8 dB ██████░░	24.8 dB ██████░░	24.8 dB ██████░░	24.8 dB ██████░░	24.8 dB ██████░░
44k1_stereo_160k	27.6 dB ███████░	27.6 dB ███████░	27.6 dB ███████░	27.6 dB ███████░	27.6 dB ███████░	27.6 dB ███████░
44k1_stereo_192k	29.9 dB ███████░	29.9 dB ███████░	29.9 dB ███████░	29.9 dB ███████░	29.9 dB ███████░	29.9 dB ███████░
44k1_stereo_256k	33.6 dB ████████	33.6 dB ████████	33.6 dB ████████	33.6 dB ████████	33.6 dB ████████	33.6 dB ████████

HE-v1 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
44k1_stereo_64k	16.8 dB ██████░░	16.5 dB ██████░░	16.7 dB ██████░░	16.7 dB ██████░░	16.7 dB ██████░░	16.7 dB ██████░░
44k1_stereo_128k	20.8 dB ███████░	20.4 dB ███████░	20.8 dB ███████░	20.7 dB ███████░	20.7 dB ███████░	20.8 dB ███████░
44k1_stereo_160k	22.3 dB ████████	21.8 dB ████████	22.2 dB ████████	22.2 dB ████████	22.2 dB ████████	22.2 dB ████████
44k1_stereo_192k	22.8 dB ████████	22.3 dB ████████	22.8 dB ████████	22.8 dB ████████	22.8 dB ████████	22.8 dB ████████
44k1_stereo_256k	23.2 dB ████████	22.6 dB ████████	23.2 dB ████████	23.2 dB ████████	23.2 dB ████████	23.2 dB ████████

HE-v2 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
44k1_stereo_64k	7.2 dB ████████	7.4 dB ████████	7.4 dB ████████	7.4 dB ████████	7.4 dB ████████	6.9 dB ███████░
44k1_stereo_128k	7.2 dB ████████	7.4 dB ████████	7.4 dB ████████	7.4 dB ████████	7.4 dB ████████	6.9 dB ███████░
44k1_stereo_160k	7.2 dB ████████	7.4 dB ████████	7.4 dB ████████	7.4 dB ████████	7.4 dB ████████	6.9 dB ███████░
44k1_stereo_192k	7.2 dB ████████	7.4 dB ████████	7.4 dB ████████	7.4 dB ████████	7.4 dB ████████	6.9 dB ███████░
44k1_stereo_256k	7.2 dB ████████	7.4 dB ████████	7.4 dB ████████	7.4 dB ████████	7.4 dB ████████	6.9 dB ███████░

Timing Alignment Delay (ms - 44.1 kHz Stereo)

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
44k1_stereo_64k	30.96 ms █░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
44k1_stereo_128k	35.19 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
44k1_stereo_160k	35.19 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
44k1_stereo_192k	35.19 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
44k1_stereo_256k	35.19 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████

HE-v1 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
44k1_stereo_64k	100.42 ms ░░░░░░░░	0.01 ms ████████	21.81 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
44k1_stereo_128k	91.83 ms █░░░░░░░	0.01 ms ████████	21.80 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
44k1_stereo_160k	91.83 ms █░░░░░░░	0.01 ms ████████	21.80 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
44k1_stereo_192k	91.83 ms █░░░░░░░	0.01 ms ████████	21.80 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
44k1_stereo_256k	91.83 ms █░░░░░░░	0.01 ms ████████	21.80 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████

HE-v2 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
44k1_stereo_64k	161.11 ms ░░░░░░░░	0.03 ms ████████	21.79 ms ███████░	0.03 ms ████████	0.03 ms ████████	0.03 ms ████████
44k1_stereo_128k	161.11 ms ░░░░░░░░	0.03 ms ████████	21.79 ms ███████░	0.03 ms ████████	0.03 ms ████████	0.03 ms ████████
44k1_stereo_160k	161.11 ms ░░░░░░░░	0.03 ms ████████	21.79 ms ███████░	0.03 ms ████████	0.03 ms ████████	0.03 ms ████████
44k1_stereo_192k	161.11 ms ░░░░░░░░	0.03 ms ████████	21.79 ms ███████░	0.03 ms ████████	0.03 ms ████████	0.03 ms ████████
44k1_stereo_256k	161.11 ms ░░░░░░░░	0.03 ms ████████	21.79 ms ███████░	0.03 ms ████████	0.03 ms ████████	0.03 ms ████████

Decoding Speed (xRT - 44.1 kHz Stereo)

xychart-beta
    title "Decoding Speed across Bitrates - 44.1 kHz Stereo (xRealtime)"
    x-axis ["64k", "128k", "160k", "192k", "256k"]
    y-axis "Speed (xRT)" 85.28 --> 200
    line "Helix AAC 1.0" [376.9699, 353.8443, 329.3958, 319.7177, 316.0548]
    line "FDK AAC 2.0.0" [306.6794, 279.1072, 271.1138, 254.3562, 259.1390]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [131.9095, 135.0499, 128.9737, 122.3967, 120.6387]
    line "Apple AAC 27.0" [176.6835, 182.1289, 172.5267, 176.4292, 174.3470]
    line "FAAD 3 (f9fbcb76)" [474.2021, 443.2514, 416.3115, 404.3310, 374.0778]
    line "FAAD 2.11.3" [349.0087, 320.0043, 330.8251, 323.8996, 300.2193]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
44k1_stereo_64k	510.4x ███████░	377.2x █████░░░	135.4x ██░░░░░░	185.1x ███░░░░░	563.7x ████████	415.7x ██████░░
44k1_stereo_128k	432.3x ██████░░	318.8x █████░░░	134.0x ██░░░░░░	188.6x ███░░░░░	504.1x ███████░	352.1x █████░░░
44k1_stereo_160k	399.1x ██████░░	308.3x ████░░░░	129.7x ██░░░░░░	178.0x ███░░░░░	465.8x ███████░	359.8x █████░░░
44k1_stereo_192k	386.6x █████░░░	288.9x ████░░░░	119.9x ██░░░░░░	183.7x ███░░░░░	450.0x ██████░░	349.0x █████░░░
44k1_stereo_256k	375.7x █████░░░	289.2x ████░░░░	119.7x ██░░░░░░	181.1x ███░░░░░	410.9x ██████░░	314.7x ████░░░░

HE-v1 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
44k1_stereo_64k	212.2x ████░░░░	244.6x █████░░░	128.6x ███░░░░░	164.6x ███░░░░░	388.0x ████████	280.2x ██████░░
44k1_stereo_128k	206.6x ████░░░░	233.7x █████░░░	139.4x ███░░░░░	172.7x ████░░░░	363.5x ███████░	273.8x ██████░░
44k1_stereo_160k	200.7x ████░░░░	230.0x █████░░░	127.5x ███░░░░░	163.6x ███░░░░░	347.3x ███████░	282.7x ██████░░
44k1_stereo_192k	192.0x ████░░░░	211.8x ████░░░░	126.4x ███░░░░░	167.5x ███░░░░░	342.0x ███████░	285.9x ██████░░
44k1_stereo_256k	194.7x ████░░░░	222.6x █████░░░	122.4x ███░░░░░	164.9x ███░░░░░	317.6x ███████░	270.6x ██████░░

HE-v2 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
44k1_stereo_64k	337.8x ███████░	210.8x ████░░░░	127.7x ███░░░░░	179.0x ████░░░░	374.9x ████████	288.8x ██████░░
44k1_stereo_128k	334.3x ███████░	211.2x █████░░░	130.5x ███░░░░░	174.9x ████░░░░	359.3x ████████	284.0x ██████░░
44k1_stereo_160k	307.9x ███████░	204.3x ████░░░░	129.1x ███░░░░░	168.5x ████░░░░	356.4x ████████	311.3x ███████░
44k1_stereo_192k	307.5x ███████░	201.5x ████░░░░	124.5x ███░░░░░	165.4x ████░░░░	346.3x ███████░	299.5x ██████░░
44k1_stereo_256k	320.2x ███████░	211.8x █████░░░	121.0x ███░░░░░	166.2x ████░░░░	339.7x ███████░	301.7x ██████░░

48 kHz Stereo

Per-Scenario Average MOS (48 kHz Stereo)

xychart-beta
    title "Decoder Perceptual Quality across Bitrates - 48 kHz Stereo (Average MOS)"
    x-axis ["24k", "32k", "40k", "48k", "56k", "64k", "96k", "128k", "160k", "192k", "256k", "320k"]
    y-axis "MOS Score" 2.603 --> 4.989
    line "Helix AAC 1.0" [2.8204, 3.3257, 3.5712, 3.8060, 4.1160, 4.2805, 4.5757, 4.6834, 4.7356, 4.7644, 4.7839, 4.7905]
    line "FDK AAC 2.0.0" [2.8023, 3.3037, 3.5505, 3.7846, 4.1034, 4.2680, 4.5632, 4.6701, 4.7219, 4.7504, 4.7697, 4.7762]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [2.8086, 3.3134, 3.5581, 3.7912, 4.1087, 4.2717, 4.5666, 4.6741, 4.7263, 4.7551, 4.7746, 4.7811]
    line "Apple AAC 27.0" [2.8093, 3.3136, 3.5569, 3.7909, 4.1092, 4.2716, 4.5665, 4.6740, 4.7263, 4.7551, 4.7746, 4.7811]
    line "FAAD 3 (f9fbcb76)" [2.8105, 3.3137, 3.5579, 3.7909, 4.1092, 4.2710, 4.5665, 4.6741, 4.7263, 4.7551, 4.7746, 4.7811]
    line "FAAD 2.11.3" [2.8033, 3.3056, 3.5513, 3.7834, 4.1049, 4.2677, 4.5616, 4.6689, 4.7209, 4.7498, 4.7692, 4.7758]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
48k_stereo_24k	2.278 ████░░░░	2.278 ████░░░░	2.278 ████░░░░	2.280 ████░░░░	2.280 ████░░░░	2.280 ████░░░░
48k_stereo_32k	2.801 ████░░░░	2.801 ████░░░░	2.801 ████░░░░	2.801 ████░░░░	2.802 ████░░░░	2.802 ████░░░░
48k_stereo_40k	3.088 █████░░░	3.088 █████░░░	3.089 █████░░░	3.086 █████░░░	3.088 █████░░░	3.091 █████░░░
48k_stereo_48k	3.485 ██████░░	3.484 ██████░░	3.484 ██████░░	3.484 ██████░░	3.484 ██████░░	3.486 ██████░░
48k_stereo_56k	3.991 ██████░░	3.992 ██████░░	3.991 ██████░░	3.992 ██████░░	3.992 ██████░░	3.991 ██████░░
48k_stereo_64k	4.234 ███████░	4.234 ███████░	4.234 ███████░	4.232 ███████░	4.232 ███████░	4.235 ███████░
48k_stereo_96k	4.693 ████████	4.693 ████████	4.694 ████████	4.693 ████████	4.694 ████████	4.694 ████████
48k_stereo_128k	4.831 ████████	4.831 ████████	4.831 ████████	4.831 ████████	4.831 ████████	4.832 ████████
48k_stereo_160k	4.899 ████████	4.899 ████████	4.899 ████████	4.899 ████████	4.899 ████████	4.899 ████████
48k_stereo_192k	4.940 ████████	4.940 ████████	4.940 ████████	4.940 ████████	4.940 ████████	4.940 ████████
48k_stereo_256k	4.969 ████████	4.969 ████████	4.969 ████████	4.969 ████████	4.969 ████████	4.969 ████████
48k_stereo_320k	4.980 ████████	4.980 ████████	4.980 ████████	4.980 ████████	4.980 ████████	4.980 ████████

HE-v1 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
48k_stereo_24k	3.154 █████░░░	3.135 █████░░░	3.155 █████░░░	3.154 █████░░░	3.157 █████░░░	3.157 █████░░░
48k_stereo_32k	3.830 ██████░░	3.800 ██████░░	3.830 ██████░░	3.830 ██████░░	3.830 ██████░░	3.830 ██████░░
48k_stereo_40k	4.100 ███████░	4.079 ███████░	4.100 ███████░	4.101 ███████░	4.101 ███████░	4.102 ███████░
48k_stereo_48k	4.236 ███████░	4.218 ███████░	4.236 ███████░	4.236 ███████░	4.235 ███████░	4.237 ███████░
48k_stereo_56k	4.388 ███████░	4.374 ███████░	4.389 ███████░	4.389 ███████░	4.389 ███████░	4.390 ███████░
48k_stereo_64k	4.496 ███████░	4.485 ███████░	4.494 ███████░	4.497 ███████░	4.496 ███████░	4.495 ███████░
48k_stereo_96k	4.706 ████████	4.695 ████████	4.706 ████████	4.706 ████████	4.706 ████████	4.707 ████████
48k_stereo_128k	4.807 ████████	4.793 ████████	4.807 ████████	4.807 ████████	4.807 ████████	4.807 ████████
48k_stereo_160k	4.853 ████████	4.838 ████████	4.853 ████████	4.853 ████████	4.853 ████████	4.853 ████████
48k_stereo_192k	4.872 ████████	4.855 ████████	4.872 ████████	4.872 ████████	4.872 ████████	4.872 ████████
48k_stereo_256k	4.882 ████████	4.865 ████████	4.882 ████████	4.882 ████████	4.882 ████████	4.882 ████████
48k_stereo_320k	4.884 ████████	4.866 ████████	4.884 ████████	4.884 ████████	4.884 ████████	4.884 ████████

HE-v2 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
48k_stereo_24k	3.404 (1ch) █████░░░	3.352 █████░░░	3.352 █████░░░	3.352 █████░░░	3.352 █████░░░	3.319 █████░░░
48k_stereo_32k	3.620 (1ch) ██████░░	3.564 ██████░░	3.564 ██████░░	3.564 ██████░░	3.564 ██████░░	3.527 ██████░░
48k_stereo_40k	3.744 (1ch) ██████░░	3.683 ██████░░	3.683 ██████░░	3.683 ██████░░	3.683 ██████░░	3.646 ██████░░
48k_stereo_48k	3.803 (1ch) ██████░░	3.737 ██████░░	3.737 ██████░░	3.737 ██████░░	3.737 ██████░░	3.699 ██████░░
48k_stereo_56k	3.799 (1ch) ██████░░	3.739 ██████░░	3.739 ██████░░	3.739 ██████░░	3.739 ██████░░	3.704 ██████░░
48k_stereo_64k	3.820 (1ch) ██████░░	3.754 ██████░░	3.754 ██████░░	3.754 ██████░░	3.754 ██████░░	3.717 ██████░░
48k_stereo_96k	3.844 (1ch) ██████░░	3.779 ██████░░	3.779 ██████░░	3.779 ██████░░	3.779 ██████░░	3.741 ██████░░
48k_stereo_128k	3.846 (1ch) ██████░░	3.779 ██████░░	3.779 ██████░░	3.779 ██████░░	3.779 ██████░░	3.742 ██████░░
48k_stereo_160k	3.847 (1ch) ██████░░	3.781 ██████░░	3.781 ██████░░	3.781 ██████░░	3.781 ██████░░	3.744 ██████░░
48k_stereo_192k	3.847 (1ch) ██████░░	3.781 ██████░░	3.781 ██████░░	3.781 ██████░░	3.781 ██████░░	3.744 ██████░░
48k_stereo_256k	3.847 (1ch) ██████░░	3.781 ██████░░	3.781 ██████░░	3.781 ██████░░	3.781 ██████░░	3.744 ██████░░
48k_stereo_320k	3.847 (1ch) ██████░░	3.781 ██████░░	3.781 ██████░░	3.781 ██████░░	3.781 ██████░░	3.744 ██████░░

Scores marked (1ch) indicate mono output on HE-v2 stereo bitstreams due to lack of Parametric Stereo decoding.

Spec Conformance (Mean SNR - 48 kHz Stereo)

xychart-beta
    title "Decoder Spec Conformance across Bitrates - 48 kHz Stereo (Mean SNR dB)"
    x-axis ["24k", "32k", "40k", "48k", "56k", "64k", "96k", "128k", "160k", "192k", "256k", "320k"]
    y-axis "SNR (dB)" 6.03 --> 30.71
    line "Helix AAC 1.0" [8.1545, 9.8627, 11.4111, 12.4588, 14.0621, 15.4070, 18.2883, 21.1958, 23.2820, 24.7733, 26.9234, 28.6291]
    line "FDK AAC 2.0.0" [8.1600, 9.8447, 11.3928, 12.4447, 14.0275, 15.3704, 18.2477, 21.1304, 23.1890, 24.6637, 26.7942, 28.4970]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [8.1894, 9.8883, 11.4398, 12.4898, 14.0756, 15.4198, 18.3029, 21.2106, 23.2981, 24.7896, 26.9381, 28.6422]
    line "Apple AAC 27.0" [8.1993, 9.8936, 11.4455, 12.4951, 14.0830, 15.4260, 18.3099, 21.2169, 23.3039, 24.7955, 26.9441, 28.6489]
    line "FAAD 3 (f9fbcb76)" [8.1981, 9.8944, 11.4456, 12.4958, 14.0830, 15.4265, 18.3099, 21.2157, 23.3024, 24.7931, 26.9412, 28.6439]
    line "FAAD 2.11.3" [8.0865, 9.7711, 11.3191, 12.3653, 14.0137, 15.3584, 18.2304, 21.1374, 23.2245, 24.7157, 26.8645, 28.5692]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
48k_stereo_24k	7.9 dB ██░░░░░░	7.9 dB ██░░░░░░	7.9 dB ██░░░░░░	7.9 dB ██░░░░░░	7.9 dB ██░░░░░░	7.9 dB ██░░░░░░
48k_stereo_32k	10.3 dB ██░░░░░░	10.3 dB ██░░░░░░	10.3 dB ██░░░░░░	10.3 dB ██░░░░░░	10.3 dB ██░░░░░░	10.3 dB ██░░░░░░
48k_stereo_40k	12.2 dB ███░░░░░	12.2 dB ███░░░░░	12.2 dB ███░░░░░	12.2 dB ███░░░░░	12.2 dB ███░░░░░	12.2 dB ███░░░░░
48k_stereo_48k	13.3 dB ███░░░░░	13.3 dB ███░░░░░	13.3 dB ███░░░░░	13.3 dB ███░░░░░	13.3 dB ███░░░░░	13.3 dB ███░░░░░
48k_stereo_56k	14.5 dB ███░░░░░	14.5 dB ███░░░░░	14.5 dB ███░░░░░	14.5 dB ███░░░░░	14.5 dB ███░░░░░	14.5 dB ███░░░░░
48k_stereo_64k	16.5 dB ████░░░░	16.5 dB ████░░░░	16.5 dB ████░░░░	16.5 dB ████░░░░	16.5 dB ████░░░░	16.5 dB ████░░░░
48k_stereo_96k	20.7 dB █████░░░	20.7 dB █████░░░	20.7 dB █████░░░	20.7 dB █████░░░	20.7 dB █████░░░	20.7 dB █████░░░
48k_stereo_128k	24.7 dB █████░░░	24.7 dB █████░░░	24.7 dB █████░░░	24.7 dB █████░░░	24.7 dB █████░░░	24.7 dB █████░░░
48k_stereo_160k	27.5 dB ██████░░	27.5 dB ██████░░	27.5 dB ██████░░	27.5 dB ██████░░	27.5 dB ██████░░	27.5 dB ██████░░
48k_stereo_192k	29.8 dB ███████░	29.8 dB ███████░	29.8 dB ███████░	29.8 dB ███████░	29.8 dB ███████░	29.8 dB ███████░
48k_stereo_256k	33.3 dB ███████░	33.3 dB ███████░	33.3 dB ███████░	33.3 dB ███████░	33.3 dB ███████░	33.3 dB ███████░
48k_stereo_320k	36.2 dB ████████	36.2 dB ████████	36.2 dB ████████	36.2 dB ████████	36.2 dB ████████	36.2 dB ████████

HE-v1 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
48k_stereo_24k	9.7 dB ███░░░░░	9.6 dB ███░░░░░	9.7 dB ███░░░░░	9.7 dB ███░░░░░	9.7 dB ███░░░░░	9.7 dB ███░░░░░
48k_stereo_32k	11.4 dB ████░░░░	11.2 dB ████░░░░	11.4 dB ████░░░░	11.4 dB ████░░░░	11.4 dB ████░░░░	11.4 dB ████░░░░
48k_stereo_40k	13.3 dB ████░░░░	13.1 dB ████░░░░	13.3 dB ████░░░░	13.3 dB ████░░░░	13.3 dB ████░░░░	13.3 dB ████░░░░
48k_stereo_48k	14.8 dB █████░░░	14.6 dB █████░░░	14.8 dB █████░░░	14.7 dB █████░░░	14.7 dB █████░░░	14.8 dB █████░░░
48k_stereo_56k	15.8 dB █████░░░	15.6 dB █████░░░	15.8 dB █████░░░	15.8 dB █████░░░	15.8 dB █████░░░	15.8 dB █████░░░
48k_stereo_64k	16.7 dB ██████░░	16.6 dB █████░░░	16.7 dB ██████░░	16.7 dB ██████░░	16.7 dB ██████░░	16.7 dB ██████░░
48k_stereo_96k	19.0 dB ██████░░	18.7 dB ██████░░	19.0 dB ██████░░	18.9 dB ██████░░	18.9 dB ██████░░	18.9 dB ██████░░
48k_stereo_128k	21.2 dB ███████░	20.9 dB ███████░	21.2 dB ███████░	21.2 dB ███████░	21.2 dB ███████░	21.2 dB ███████░
48k_stereo_160k	22.8 dB ████████	22.4 dB ███████░	22.8 dB ████████	22.8 dB ████████	22.8 dB ████████	22.8 dB ████████
48k_stereo_192k	23.5 dB ████████	23.0 dB ████████	23.5 dB ████████	23.5 dB ████████	23.5 dB ████████	23.5 dB ████████
48k_stereo_256k	24.1 dB ████████	23.5 dB ████████	24.1 dB ████████	24.0 dB ████████	24.0 dB ████████	24.0 dB ████████
48k_stereo_320k	24.1 dB ████████	23.6 dB ████████	24.1 dB ████████	24.1 dB ████████	24.1 dB ████████	24.1 dB ████████

HE-v2 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
48k_stereo_24k	6.2 dB ███████░	6.4 dB ███████░	6.4 dB ███████░	6.4 dB ███████░	6.4 dB ███████░	5.9 dB ██████░░
48k_stereo_32k	6.7 dB ███████░	6.9 dB ███████░	6.9 dB ███████░	6.9 dB ███████░	6.9 dB ███████░	6.3 dB ███████░
48k_stereo_40k	7.0 dB ████████	7.2 dB ████████	7.2 dB ████████	7.2 dB ████████	7.2 dB ████████	6.7 dB ███████░
48k_stereo_48k	7.3 dB ████████	7.4 dB ████████	7.4 dB ████████	7.4 dB ████████	7.4 dB ████████	6.9 dB ███████░
48k_stereo_56k	7.2 dB ████████	7.4 dB ████████	7.3 dB ████████	7.4 dB ████████	7.4 dB ████████	6.8 dB ███████░
48k_stereo_64k	7.2 dB ████████	7.4 dB ████████	7.3 dB ████████	7.4 dB ████████	7.4 dB ████████	6.9 dB ███████░
48k_stereo_96k	7.3 dB ████████	7.5 dB ████████	7.4 dB ████████	7.5 dB ████████	7.5 dB ████████	6.9 dB ███████░
48k_stereo_128k	7.3 dB ████████	7.5 dB ████████	7.4 dB ████████	7.5 dB ████████	7.5 dB ████████	6.9 dB ███████░
48k_stereo_160k	7.3 dB ████████	7.5 dB ████████	7.4 dB ████████	7.5 dB ████████	7.5 dB ████████	6.9 dB ███████░
48k_stereo_192k	7.3 dB ████████	7.5 dB ████████	7.4 dB ████████	7.5 dB ████████	7.5 dB ████████	6.9 dB ███████░
48k_stereo_256k	7.3 dB ████████	7.5 dB ████████	7.4 dB ████████	7.5 dB ████████	7.5 dB ████████	6.9 dB ███████░
48k_stereo_320k	7.3 dB ████████	7.5 dB ████████	7.4 dB ████████	7.5 dB ████████	7.5 dB ████████	6.9 dB ███████░

Timing Alignment Delay (ms - 48 kHz Stereo)

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
48k_stereo_24k	28.34 ms █░░░░░░░	0.16 ms ████████	0.13 ms ████████	0.15 ms ████████	0.14 ms ████████	0.13 ms ████████
48k_stereo_32k	28.44 ms █░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
48k_stereo_40k	28.44 ms █░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
48k_stereo_48k	28.44 ms █░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
48k_stereo_56k	28.44 ms █░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
48k_stereo_64k	28.44 ms █░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
48k_stereo_96k	32.33 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
48k_stereo_128k	32.33 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
48k_stereo_160k	32.33 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
48k_stereo_192k	32.33 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
48k_stereo_256k	32.33 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████
48k_stereo_320k	32.33 ms ░░░░░░░░	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████	0.00 ms ████████

HE-v1 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
48k_stereo_24k	84.36 ms █░░░░░░░	0.01 ms ████████	20.03 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
48k_stereo_32k	84.36 ms █░░░░░░░	0.02 ms ████████	20.03 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
48k_stereo_40k	92.26 ms ░░░░░░░░	0.01 ms ████████	20.03 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
48k_stereo_48k	92.26 ms ░░░░░░░░	0.01 ms ████████	20.03 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
48k_stereo_56k	92.26 ms ░░░░░░░░	0.01 ms ████████	20.03 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
48k_stereo_64k	92.26 ms ░░░░░░░░	0.01 ms ████████	20.04 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
48k_stereo_96k	84.37 ms █░░░░░░░	0.01 ms ████████	20.03 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
48k_stereo_128k	84.37 ms █░░░░░░░	0.01 ms ████████	20.03 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
48k_stereo_160k	84.37 ms █░░░░░░░	0.01 ms ████████	20.03 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
48k_stereo_192k	84.37 ms █░░░░░░░	0.01 ms ████████	20.03 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
48k_stereo_256k	84.37 ms █░░░░░░░	0.01 ms ████████	20.03 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████
48k_stereo_320k	84.37 ms █░░░░░░░	0.01 ms ████████	20.03 ms ██████░░	0.01 ms ████████	0.01 ms ████████	0.01 ms ████████

HE-v2 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
48k_stereo_24k	128.01 ms █░░░░░░░	0.03 ms ████████	20.01 ms ███████░	0.03 ms ████████	0.03 ms ████████	0.03 ms ████████
48k_stereo_32k	128.01 ms █░░░░░░░	0.03 ms ████████	20.01 ms ███████░	0.03 ms ████████	0.03 ms ████████	0.03 ms ████████
48k_stereo_40k	128.01 ms █░░░░░░░	0.03 ms ████████	20.01 ms ███████░	0.03 ms ████████	0.03 ms ████████	0.03 ms ████████
48k_stereo_48k	128.01 ms █░░░░░░░	0.03 ms ████████	20.01 ms ███████░	0.03 ms ████████	0.03 ms ████████	0.03 ms ████████
48k_stereo_56k	147.99 ms ░░░░░░░░	0.06 ms ████████	19.99 ms ███████░	0.06 ms ████████	0.06 ms ████████	0.06 ms ████████
48k_stereo_64k	147.99 ms ░░░░░░░░	0.06 ms ████████	19.99 ms ███████░	0.06 ms ████████	0.06 ms ████████	0.06 ms ████████
48k_stereo_96k	147.99 ms ░░░░░░░░	0.06 ms ████████	19.99 ms ███████░	0.06 ms ████████	0.06 ms ████████	0.06 ms ████████
48k_stereo_128k	147.99 ms ░░░░░░░░	0.06 ms ████████	19.99 ms ███████░	0.06 ms ████████	0.06 ms ████████	0.06 ms ████████
48k_stereo_160k	147.99 ms ░░░░░░░░	0.06 ms ████████	19.99 ms ███████░	0.06 ms ████████	0.06 ms ████████	0.06 ms ████████
48k_stereo_192k	147.99 ms ░░░░░░░░	0.06 ms ████████	19.99 ms ███████░	0.06 ms ████████	0.06 ms ████████	0.06 ms ████████
48k_stereo_256k	147.99 ms ░░░░░░░░	0.06 ms ████████	19.99 ms ███████░	0.06 ms ████████	0.06 ms ████████	0.06 ms ████████
48k_stereo_320k	147.99 ms ░░░░░░░░	0.06 ms ████████	19.99 ms ███████░	0.06 ms ████████	0.06 ms ████████	0.06 ms ████████

Decoding Speed (xRT - 48 kHz Stereo)

xychart-beta
    title "Decoding Speed across Bitrates - 48 kHz Stereo (xRealtime)"
    x-axis ["24k", "32k", "40k", "48k", "56k", "64k", "96k", "128k", "160k", "192k", "256k", "320k"]
    y-axis "Speed (xRT)" 84 --> 200
    line "Helix AAC 1.0" [426.0604, 394.5801, 376.9296, 363.0019, 333.2439, 341.9721, 323.0202, 317.8209, 306.0912, 298.0046, 270.8302, 262.6450]
    line "FDK AAC 2.0.0" [342.2242, 313.6685, 309.4781, 285.0550, 292.8186, 287.3344, 263.4180, 255.2864, 238.9874, 242.0014, 233.1380, 236.1786]
    line "FFmpeg AAC N-126786-g3fc4f99a79" [131.6780, 138.8394, 131.9305, 135.0919, 136.1328, 134.5948, 134.1701, 130.7614, 130.1114, 126.2803, 127.7449, 123.5963]
    line "Apple AAC 27.0" [180.8001, 176.3110, 175.9057, 174.0911, 170.9538, 174.1598, 159.4808, 165.4691, 179.5839, 178.6036, 173.8136, 193.0107]
    line "FAAD 3 (f9fbcb76)" [519.5780, 492.0878, 475.5820, 446.5402, 450.4920, 430.9468, 420.2961, 389.3968, 398.6488, 394.3761, 370.2523, 331.0306]
    line "FAAD 2.11.3" [396.8935, 382.6077, 359.3876, 341.5983, 367.2826, 352.2574, 337.8924, 310.5881, 286.4024, 273.4340, 260.4886, 249.8170]

LC Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
48k_stereo_24k	596.1x ███████░	451.0x ██████░░	135.5x ██░░░░░░	192.3x ██░░░░░░	652.8x ████████	470.4x ██████░░
48k_stereo_32k	549.6x ███████░	414.4x █████░░░	144.3x ██░░░░░░	189.3x ██░░░░░░	616.9x ████████	460.2x ██████░░
48k_stereo_40k	534.4x ███████░	417.3x █████░░░	136.8x ██░░░░░░	190.5x ██░░░░░░	609.0x ███████░	426.4x █████░░░
48k_stereo_48k	510.7x ██████░░	370.9x █████░░░	139.0x ██░░░░░░	188.5x ██░░░░░░	550.8x ███████░	398.4x █████░░░
48k_stereo_56k	450.7x ██████░░	367.6x █████░░░	138.2x ██░░░░░░	182.8x ██░░░░░░	541.5x ███████░	432.5x █████░░░
48k_stereo_64k	462.1x ██████░░	358.9x ████░░░░	136.8x ██░░░░░░	181.5x ██░░░░░░	508.6x ██████░░	414.2x █████░░░
48k_stereo_96k	400.5x █████░░░	307.7x ████░░░░	133.7x ██░░░░░░	165.5x ██░░░░░░	475.7x ██████░░	375.5x █████░░░
48k_stereo_128k	388.0x █████░░░	294.6x ████░░░░	132.2x ██░░░░░░	171.4x ██░░░░░░	436.7x █████░░░	340.5x ████░░░░
48k_stereo_160k	373.3x █████░░░	272.7x ███░░░░░	129.6x ██░░░░░░	186.4x ██░░░░░░	452.1x ██████░░	312.9x ████░░░░
48k_stereo_192k	359.9x ████░░░░	274.6x ███░░░░░	124.5x ██░░░░░░	183.9x ██░░░░░░	445.5x █████░░░	294.3x ████░░░░
48k_stereo_256k	320.6x ████░░░░	260.7x ███░░░░░	128.9x ██░░░░░░	181.6x ██░░░░░░	407.3x █████░░░	277.0x ███░░░░░
48k_stereo_320k	303.4x ████░░░░	263.9x ███░░░░░	121.2x █░░░░░░░	198.4x ██░░░░░░	356.8x ████░░░░	258.4x ███░░░░░

HE-v1 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
48k_stereo_24k	261.0x █████░░░	293.0x █████░░░	132.9x ██░░░░░░	172.5x ███░░░░░	447.9x ████████	355.6x ██████░░
48k_stereo_32k	225.8x ████░░░░	258.5x █████░░░	137.3x ██░░░░░░	167.1x ███░░░░░	420.3x ████████	332.2x ██████░░
48k_stereo_40k	201.2x ████░░░░	237.1x ████░░░░	130.9x ██░░░░░░	165.5x ███░░░░░	380.5x ███████░	305.6x █████░░░
48k_stereo_48k	196.0x ████░░░░	231.6x ████░░░░	133.2x ██░░░░░░	161.9x ███░░░░░	372.7x ███████░	297.7x █████░░░
48k_stereo_56k	187.4x ███░░░░░	225.7x ████░░░░	136.7x ██░░░░░░	158.5x ███░░░░░	363.1x ██████░░	302.4x █████░░░
48k_stereo_64k	190.4x ███░░░░░	223.7x ████░░░░	132.7x ██░░░░░░	164.1x ███░░░░░	355.9x ██████░░	294.1x █████░░░
48k_stereo_96k	178.6x ███░░░░░	211.0x ████░░░░	134.9x ██░░░░░░	151.2x ███░░░░░	353.2x ██████░░	288.2x █████░░░
48k_stereo_128k	184.5x ███░░░░░	210.9x ████░░░░	130.6x ██░░░░░░	157.2x ███░░░░░	332.0x ██████░░	263.7x █████░░░
48k_stereo_160k	179.3x ███░░░░░	199.4x ████░░░░	132.0x ██░░░░░░	168.2x ███░░░░░	327.9x ██████░░	249.6x ████░░░░
48k_stereo_192k	177.5x ███░░░░░	205.1x ████░░░░	130.7x ██░░░░░░	169.6x ███░░░░░	320.4x ██████░░	237.5x ████░░░░
48k_stereo_256k	167.3x ███░░░░░	203.6x ████░░░░	127.2x ██░░░░░░	162.0x ███░░░░░	323.1x ██████░░	229.6x ████░░░░
48k_stereo_320k	170.1x ███░░░░░	204.3x ████░░░░	128.2x ██░░░░░░	183.0x ███░░░░░	290.5x █████░░░	235.0x ████░░░░

HE-v2 Profile

Scenario	Helix AAC 1.0	FDK AAC 2.0.0	FFmpeg AAC N-126786-g3fc4f99a79	Apple AAC 27.0	FAAD 3 (f9fbcb76)	FAAD 2.11.3
48k_stereo_24k	333.6x ███████░	198.5x ████░░░░	122.2x ███░░░░░	170.2x ████░░░░	360.7x ████████	311.7x ███████░
48k_stereo_32k	337.8x ███████░	194.9x ████░░░░	130.2x ███░░░░░	164.2x ████░░░░	350.2x ████████	303.0x ███████░
48k_stereo_40k	325.6x ███████░	202.5x ████░░░░	123.7x ███░░░░░	162.4x ████░░░░	351.4x ████████	306.0x ███████░
48k_stereo_48k	318.1x ███████░	193.6x ████░░░░	130.0x ███░░░░░	163.7x ████░░░░	348.8x ████████	293.9x ███████░
48k_stereo_56k	300.7x ███████░	195.1x ████░░░░	126.2x ███░░░░░	160.9x ████░░░░	348.8x ████████	301.3x ███████░
48k_stereo_64k	316.1x ███████░	192.2x ████░░░░	131.5x ███░░░░░	174.9x ████░░░░	345.4x ████████	278.7x ██████░░
48k_stereo_96k	302.0x ███████░	191.3x ████░░░░	134.5x ███░░░░░	152.1x ███░░░░░	332.6x ███████░	287.0x ██████░░
48k_stereo_128k	303.7x ███████░	186.7x ████░░░░	125.3x ███░░░░░	158.1x ████░░░░	315.1x ███████░	284.9x ██████░░
48k_stereo_160k	291.0x ██████░░	183.1x ████░░░░	128.5x ███░░░░░	175.0x ████░░░░	326.4x ███████░	254.3x ██████░░
48k_stereo_192k	291.6x ██████░░	185.5x ████░░░░	124.8x ███░░░░░	175.3x ████░░░░	338.0x ███████░	261.8x ██████░░
48k_stereo_256k	278.9x ██████░░	181.9x ████░░░░	124.4x ███░░░░░	166.1x ████░░░░	316.5x ███████░	256.2x ██████░░
48k_stereo_320k	284.7x ██████░░	189.1x ████░░░░	123.9x ███░░░░░	191.6x ████░░░░	309.2x ███████░	245.2x █████░░░

44.1 kHz 5.1 Surround

Per-Scenario Average MOS (44.1 kHz 5.1 Surround)

Spec Conformance (Mean SNR - 44.1 kHz 5.1 Surround)

Timing Alignment Delay (ms - 44.1 kHz 5.1 Surround)

Decoding Speed (xRT - 44.1 kHz 5.1 Surround)

Decoder Efficiency & Footprint

Decoding Speed (xRT)

xychart-beta
    title "Average Decoding Throughput (xRealtime, Higher is Better)"
    x-axis ["Helix AAC 1.0", "FDK AAC 2.0.0", "FFmpeg AAC N-126786-g3fc4f99a79", "Apple AAC 27.0", "FAAD 3 (f9fbcb76)", "FAAD 2.11.3"]
    y-axis "Speed (xRT)" 0 --> 613
    bar "Decoding Speed" [426.1, 344.1, 135.1, 174.4, 490.3, 376.8]

🐛 View Quality Outliers (Issues Worth Investigating)

Decoder Quality Outliers (Issues Worth Investigating)

Note: Flags clips where this decoder scored ≥0.75 MOS lower than the average of all other decoders on the exact same clip or produced mono output on stereo bitstreams.

Decoder	Profile	Scenario	Outlier Clip	Decoder MOS	Peer Avg MOS	Defect Gap	Issue / Cause
Helix AAC 1.0	HE-v2	48k_stereo_256k	`mof.wav`	1.83	4.86	-3.03 MOS	Mono output (No PS)
FAAD 2.11.3	HE-v1	32k_stereo_96k	`mof.wav`	1.72	4.54	-2.83 MOS	MOS quality gap vs peers
FAAD 2.11.3	HE-v2	32k_stereo_96k	`mof.wav`	1.72	4.54	-2.83 MOS	MOS quality gap vs peers
FAAD 2.11.3	HE-v2	48k_stereo_320k	`mof.wav`	1.77	4.31	-2.53 MOS	MOS quality gap vs peers
FAAD 2.11.3	HE-v2	44k1_stereo_256k	`mof.wav`	1.75	4.28	-2.53 MOS	MOS quality gap vs peers
Helix AAC 1.0	HE-v2	48k_stereo_320k	`mof.wav`	1.83	4.30	-2.47 MOS	Mono output (No PS)
Helix AAC 1.0	HE-v2	44k1_stereo_256k	`mof.wav`	1.82	4.26	-2.44 MOS	Mono output (No PS)
FAAD 2.11.3	LC	44k1_stereo_256k	`girl.16b48k.wav`	3.41	4.73	-1.32 MOS	MOS quality gap vs peers
FAAD 2.11.3	HE-v1	48k_stereo_320k	`qrt.wav`	3.41	4.66	-1.25 MOS	MOS quality gap vs peers
FDK AAC 2.0.0	HE-v1	48k_stereo_24k	`12-German-male-speech.441.16b48k.wav`	1.83	3.08	-1.25 MOS	MOS quality gap vs peers
FAAD 2.11.3	HE-v1	48k_stereo_192k	`qrt.wav`	3.41	4.63	-1.22 MOS	MOS quality gap vs peers
FAAD 2.11.3	HE-v1	44k1_stereo_192k	`qrt.wav`	3.41	4.63	-1.22 MOS	MOS quality gap vs peers
Helix AAC 1.0	HE-v2	48k_stereo_48k	`mof.wav`	2.23	3.44	-1.21 MOS	Mono output (No PS)
FAAD 2.11.3	HE-v1	44k1_stereo_160k	`qrt.wav`	3.41	4.60	-1.19 MOS	MOS quality gap vs peers
Helix AAC 1.0	HE-v1	48k_stereo_128k	`Severance__1.31-1.51_.16b48k.wav`	3.18	4.36	-1.18 MOS	MOS quality gap vs peers
FAAD 2.11.3	HE-v1	48k_stereo_160k	`qrt.wav`	3.41	4.59	-1.18 MOS	MOS quality gap vs peers
FAAD 2.11.3	HE-v1	44k1_stereo_256k	`qrt.wav`	3.41	4.35	-0.94 MOS	MOS quality gap vs peers
FAAD 2.11.3	HE-v1	48k_stereo_256k	`qrt.wav`	3.41	4.34	-0.93 MOS	MOS quality gap vs peers
FFmpeg AAC N-126786-g3fc4f99a79	HE-v1	48k_stereo_256k	`qrt.wav`	3.41	4.34	-0.93 MOS	MOS quality gap vs peers
FAAD 3 (f9fbcb76)	HE-v1	44k1_stereo_256k	`qrt.wav`	3.43	4.35	-0.92 MOS	MOS quality gap vs peers
FAAD 2.11.3	LC	48k_stereo_256k	`girl.16b48k.wav`	3.57	4.48	-0.91 MOS	MOS quality gap vs peers
FAAD 2.11.3	LC	48k_stereo_320k	`24-Greensleeves-Korean-male-speech.441.16b48k.wav`	3.88	4.79	-0.91 MOS	MOS quality gap vs peers
FFmpeg AAC N-126786-g3fc4f99a79	HE-v2	48k_stereo_56k	`mof.wav`	3.03	3.94	-0.91 MOS	MOS quality gap vs peers
FFmpeg AAC N-126786-g3fc4f99a79	LC	48k_stereo_256k	`girl.16b48k.wav`	3.60	4.47	-0.87 MOS	MOS quality gap vs peers
Helix AAC 1.0	HE-v1	48k_stereo_320k	`qrt.wav`	3.72	4.59	-0.87 MOS	MOS quality gap vs peers
Helix AAC 1.0	HE-v1	48k_stereo_192k	`qrt.wav`	3.72	4.56	-0.84 MOS	MOS quality gap vs peers
Helix AAC 1.0	HE-v1	48k_stereo_160k	`qrt.wav`	3.72	4.52	-0.80 MOS	MOS quality gap vs peers
Apple AAC 27.0	HE-v1	48k_stereo_32k	`24-Greensleeves-Korean-male-speech.441.16b48k.wav`	2.31	3.09	-0.78 MOS	MOS quality gap vs peers
FAAD 3 (f9fbcb76)	HE-v1	48k_stereo_32k	`24-Greensleeves-Korean-male-speech.441.16b48k.wav`	2.31	3.09	-0.77 MOS	MOS quality gap vs peers
FDK AAC 2.0.0	HE-v1	48k_stereo_32k	`24-Greensleeves-Korean-male-speech.441.16b48k.wav`	2.32	3.09	-0.77 MOS	MOS quality gap vs peers
Helix AAC 1.0	HE-v1	44k1_stereo_192k	`qrt.wav`	3.79	4.55	-0.76 MOS	MOS quality gap vs peers

Decoder Metric Legend:

Ranking: by 1st Percentile MOS ($P_1$), then Overall MOS as tiebreaker.
1st Percentile MOS ($P_1$): Score threshold that 99% of tested clips equal or exceed (Higher is Better)
Overall MOS: Perceptual audio quality averaged across all scenarios (1-5, Higher is Better)
Stereo Fidelity: Faithfulness of stereo image (0-1, Higher is Better)
Mean SNR: Specification conformance signal-to-noise ratio in dB vs reference decode (Higher is Better)
Timing Error: Sample alignment offset delay in ms (Lower is Better)
Speed: Decoding throughput in xRealtime (Higher is Better)
Peak RAM: Peak dynamic memory allocation during decode (Lower is Better)
ROM (Flash): Decoder binary code + read-only + initialized data size (.text + .rodata + .data, Lower is Better)

Generated by faac-benchmark version dc50d3d (2026-09-29 18:53:53 UTC).

AAC Codec Leaderboard (FAAC 2.2.0) #90

Uh oh!

nschimme Sep 29, 2026 Maintainer

🎛️ Audio Codec Leaderboard

🎙️ Encoder Leaderboard

Overall Encoder Rankings

Per-Scenario Breakdown & Visualizations

16 kHz Mono Speech Quality Across Bitrates

Per-Scenario Average MOS (16 kHz Mono Speech)

LC Profile

Per-Scenario 1st Percentile MOS ($P_1$) (16 kHz Mono Speech)

LC Profile

Transient Fidelity (16 kHz Mono Speech)

LC Profile

Encoding Speed (16 kHz Mono Speech)

Bitrate Accuracy (16 kHz Mono Speech)

LC Profile

24 kHz Mono Speech Quality Across Bitrates

Per-Scenario Average MOS (24 kHz Mono Speech)

LC Profile

Per-Scenario 1st Percentile MOS ($P_1$) (24 kHz Mono Speech)

LC Profile

Transient Fidelity (24 kHz Mono Speech)

LC Profile

Encoding Speed (24 kHz Mono Speech)

Bitrate Accuracy (24 kHz Mono Speech)

LC Profile

32 kHz Stereo Quality Across Bitrates

Per-Scenario Average MOS (32 kHz Stereo)

LC Profile

HE-v1 Profile

HE-v2 Profile

Per-Scenario 1st Percentile MOS ($P_1$) (32 kHz Stereo)

LC Profile

HE-v1 Profile

HE-v2 Profile

Stereo Image Fidelity (32 kHz Stereo)

LC Profile

HE-v1 Profile

HE-v2 Profile

Transient Fidelity (32 kHz Stereo)

LC Profile

HE-v1 Profile

HE-v2 Profile

Encoding Speed (32 kHz Stereo)

Bitrate Accuracy (32 kHz Stereo)

LC Profile

HE-v1 Profile

HE-v2 Profile

44.1 kHz Stereo Quality Across Bitrates

Per-Scenario Average MOS (44.1 kHz Stereo)

LC Profile

HE-v1 Profile

HE-v2 Profile

Per-Scenario 1st Percentile MOS ($P_1$) (44.1 kHz Stereo)

LC Profile

HE-v1 Profile

HE-v2 Profile

Stereo Image Fidelity (44.1 kHz Stereo)

LC Profile

HE-v1 Profile

HE-v2 Profile

Transient Fidelity (44.1 kHz Stereo)

LC Profile

HE-v1 Profile

HE-v2 Profile

Encoding Speed (44.1 kHz Stereo)

Bitrate Accuracy (44.1 kHz Stereo)

LC Profile

HE-v1 Profile

HE-v2 Profile

48 kHz Stereo Quality Across Bitrates

Per-Scenario Average MOS (48 kHz Stereo)

LC Profile

HE-v1 Profile

HE-v2 Profile

Per-Scenario 1st Percentile MOS ($P_1$) (48 kHz Stereo)

LC Profile

HE-v1 Profile

HE-v2 Profile

nschimme
Sep 29, 2026
Maintainer