oxideav-dts

Pure-Rust DTS Coherent Acoustics (also known as DCA, Digital Theater Systems, "DTS Core") audio decoder for the oxideav framework.

Status

Round-1 scaffold (the DTS Core profile, 16-bit, 1.5 Mbit/s typical DVD-Video / Blu-ray rate). Decodes the original 1995-vintage backwards-compatible Core layer — the foundation every DTS-HD frame also carries.

Layer / feature	Round-1
Sync detection (0x7FFE_8001 BE 16-bit)	Y
Frame header parse (104/120 bits)	Y
AMODE 0..15 (mono → 5.1 + matrix layouts)	Y
Sample rates 8 kHz .. 192 kHz (table-driven)	Y
Bit rates 32 kbps .. 3.84 Mbps + lossless sentinel	Y
Audio coding header (subframes / SUBS / SUBVQ / …)	Y
Bit-allocated subbands (BHUFF 5/6/7 = direct-width)	Y
Direct 6/7-bit absolute scale factors (SHUFF 5/6)	Y
32-band polyphase synthesis (PQF) — synthesised proto	Approx
VQ codebook lookup (16 of 1024 entries embedded)	Approx
BHUFF Huffman codebooks 0..4	-
SHUFF Huffman codebooks 0..4	-
THUFF transition modes (full per-sample TM resolve)	-
Joint-intensity coding (JCH > 0)	-
ADPCM prediction VQ (4096-entry codebook)	-
LFE channel (8-bit ADPCM + 64×/128× FIR)	-
Auxiliary data block + dynamic downmix	-
14-bit packed core / LE byte-order variants	-
Encoder	-

Backlog (round 2+)

• PQF prototype window — round-1 ships a synthesised Kaiser-windowed-sinc prototype (compatible shape, ~96 dB stop-band) so PSNR sits ~30-40 dB on bit-allocated content. Bit-exact reconstruction needs the full 512-tap ff_dca_fir_32bands_* tables from docs/audio/dts/data/dts-pqf-window.md; only the first 32 taps are inline today.
• VQ codebook (1008 of 1024 entries) — the inline sidecar currently lists only entries 0..15 verbatim. The remaining 1008 are documented as dcadata.c lines 4240..6290 but cannot be copied here under the workspace's clean-room policy. PSNR on high-frequency-rich material (cymbals / consonants) is throttled by this gap until docs land the full table.
• Huffman codebooks — round-1 supports the encoder fast-path (BHUFF/SHUFF = direct fixed-width). The 60+ Huffman codebooks for bit-allocation, transition mode, scale factor, and quantization index are defined in dts-huffman-tables.md (sizes 3..13 inline, sizes 17/25/33/65/129 deferred) and will land progressively.
• Adaptive predictor — 4096-entry × 4-coef ADPCM codebook (dts-pqf-window.md §7) is documented at first 4 entries only; full table needed before prediction_mode bits can be honoured.
• LFE channel — separate 8-bit ADPCM path with 64-/128-tap upsamplers; tables in dts-pqf-window.md §6 (truncated). LFE is required for 5.1 → produce a silent LFE today.
• EXSS framework — extension-substream container (dts-trace-reverse-engineering.md §4). Required for any DTS-HD MA / HRA stream regardless of XLL/XBR.
• XLL — DTS-HD Master Audio lossless residual; full chset hierarchy + Rice/hybrid-Rice entropy + LPC reconstruction (dts-xll-tables.md partly drafted, scaffold staged for round 2+).
• XCH / XXCH — 6.1 / 7.1 back-surround additive channels.
• X96 — 96-kHz core extension with cross-band assembly.
• XBR — extended-bit-rate residual companion.
• LBR / DTS Express — secondary-audio low-bit-rate codec (dts-lbr-tables.md partly drafted, blocked on a secondary-audio fixture sample).
• 14-bit packed core / LE byte-swap variants — for CD-DA / S/PDIF interop; sync-word table already has the constants.

Provenance

This crate is a clean-room implementation against the public ETSI TS 102 114 standard. The reference material lives entirely in docs/audio/dts/:

• docs/audio/dts/dts-trace-reverse-engineering.md — bitstream structure + frame-level walk-through.
• docs/audio/dts/data/dts-core-tables.md — AMODE, SFREQ, RATE, PCMR, scale-factor LUTs, quantizer step tables, dmix LUT, LFE step LUTs.
• docs/audio/dts/data/dts-huffman-tables.md — VLC inventory and inline sub-tables for sizes 3..13.
• docs/audio/dts/data/dts-pqf-window.md — synthesis-bank prototype description (first 32 taps inline) + LFE filter outlines.
• docs/audio/dts/data/dts-vq-codebook.md — high-frequency VQ codebook geometry + first 16 entries inline.

No FFmpeg, libdcadec, or libdca source has been consulted.

License

MIT — see LICENSE.