AAC Encoder Leaderboard (FAAC 2.0.0)

[nschimme]

Run on a Macbook Pro M1 32GB (commit 8195aa8)

• FAAC 2.0.0
• fdk-aac 2.0.3
• ffmpeg 8.1.2
• Apple AAC 26.5.2 (25F84)

AAC Encoder Leaderboard

Overall Rankings

Rank	Encoder	Status	Avg MOS	Worst MOS	Stereo Fidelity	Speed (xRT)	Bitrate Error	Footprint
🏆 1	Apple AAC	OK	3.963	1.390	0.9360	111.9x	6.2%	353.3 KB
2	aac-enc	OK	3.912	1.334	0.9548	159.6x	1.9%	1124.9 KB
3	FAAC	OK	3.876	2.165	0.9755	544.9x	6.0%	116.0 KB
4	FFmpeg AAC	OK	3.258	1.369	0.9460	40.6x	8.2%	431.4 KB

Per-Scenario Quality (MOS)

Scenario	Apple AAC	aac-enc	FAAC	FFmpeg AAC
16k_mono_16k	3.180	3.264	3.756	3.147
16k_mono_40k	4.234	4.196	4.197	3.992
48k_stereo_24k	2.290	3.122	3.280	1.774
48k_stereo_32k	3.521	3.556	3.326	1.796
48k_stereo_40k	4.121	3.887	3.359	1.845
48k_stereo_48k	4.196	3.960	3.379	2.048
48k_stereo_56k	4.361	4.211	3.393	2.593
48k_stereo_64k	3.192	3.485	3.350	3.187
48k_stereo_96k	4.142	3.851	3.892	4.065
48k_stereo_128k	4.398	4.144	4.519	4.292
48k_stereo_160k	4.530	4.299	4.589	4.414
48k_stereo_192k	4.633	4.430	4.646	4.517
48k_stereo_256k	4.716	4.448	4.697	4.680

Per-Scenario Stereo Fidelity

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

Scenario	Apple AAC	aac-enc	FAAC	FFmpeg AAC
16k_mono_16k	N/A	N/A	N/A	N/A
16k_mono_40k	N/A	N/A	N/A	N/A
48k_stereo_24k	0.8037	0.8982	0.9130	0.7282
48k_stereo_32k	0.8448	0.9073	0.9506	0.8852
48k_stereo_40k	0.9003	0.9117	0.9661	0.9425
48k_stereo_48k	0.9037	0.9133	0.9741	0.9571
48k_stereo_56k	0.9046	0.9156	0.9789	0.9652
48k_stereo_64k	0.9767	0.9833	0.9801	0.9721
48k_stereo_96k	0.9857	0.9912	0.9888	0.9853
48k_stereo_128k	0.9906	0.9947	0.9924	0.9896
48k_stereo_160k	0.9935	0.9953	0.9942	0.9918
48k_stereo_192k	0.9954	0.9959	0.9955	0.9932
48k_stereo_256k	0.9967	0.9963	0.9968	0.9960

Per-Scenario Bitrate Accuracy (Error %)

Scenario	Apple AAC	aac-enc	FAAC	FFmpeg AAC
16k_mono_16k	15.1%	2.2%	9.6%	20.3%
16k_mono_40k	16.6%	2.0%	22.9%	24.2%
48k_stereo_24k	7.4%	5.1%	3.4%	13.7%
48k_stereo_32k	5.1%	3.4%	3.7%	6.9%
48k_stereo_40k	5.3%	2.6%	3.8%	6.5%
48k_stereo_48k	4.7%	2.0%	3.7%	5.8%
48k_stereo_56k	4.5%	1.8%	3.3%	5.5%
48k_stereo_64k	3.9%	1.7%	6.3%	4.9%
48k_stereo_96k	4.3%	1.1%	5.3%	3.6%
48k_stereo_128k	3.3%	0.8%	5.7%	3.7%
48k_stereo_160k	3.6%	0.7%	4.8%	3.8%
48k_stereo_192k	3.9%	0.6%	3.6%	3.8%
48k_stereo_256k	3.0%	0.5%	1.9%	3.7%

Per-Scenario Efficiency (Speed xRT)

Scenario	Apple AAC	aac-enc	FAAC	FFmpeg AAC
16k_mono_16k	177.8x	519.3x	787.8x	104.5x
16k_mono_40k	179.3x	446.8x	873.5x	81.5x
48k_stereo_24k	149.7x	104.0x	480.0x	37.4x
48k_stereo_32k	127.6x	103.0x	508.1x	33.2x
48k_stereo_40k	107.9x	97.3x	501.6x	31.9x
48k_stereo_48k	102.1x	91.9x	491.6x	29.7x
48k_stereo_56k	102.7x	90.2x	494.6x	30.5x
48k_stereo_64k	104.5x	113.4x	546.6x	28.8x
48k_stereo_96k	82.4x	109.3x	524.7x	29.2x
48k_stereo_128k	83.0x	105.1x	480.3x	29.6x
48k_stereo_160k	82.1x	102.5x	465.6x	29.9x
48k_stereo_192k	78.6x	98.2x	480.8x	28.0x
48k_stereo_256k	77.3x	94.2x	448.3x	33.6x

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Metric Legend:

• Avg MOS: Perceptual quality (1-5, Higher is Better)
• Stereo Fidelity: Faithfulness of stereo image (0-1, Higher is Better)
• Speed: Encoding throughput (Higher is Better)
• Bitrate Error: Absolute deviation from target bitrate (Lower is Better)
• Footprint: Codec shared-library size (falls back to the host binary if statically linked) (Lower is Better)

[nschimme]

These results are referenced by https://hydrogenaudio.org/index.php/topic,129764.new.html and https://nils.schimmelmann.us/2026-07-23-faac-20-a-free-fast-aac-encoder-built-for-the-edge/