oxideav-cook

Pure-Rust RealAudio Cook (RealNetworks G2 / "Cooker") audio decoder for the oxideav media framework.

Cook is the audio codec used inside RealMedia (*.rm / *.ra / *.rmvb) containers — sub-band MDCT-based, lossy, with a fixed XOR obfuscation layer, a differentially-coded subband-envelope scheme, and seven Huffman-coded scalar-quantized vector tables that pack 20 coefficients per subband. JOINT_STEREO mode adds a unit-norm matrix decoupling step; MC_COOK chains independent single-stream cooks for multichannel layouts (5.1 / 7.1).

Coverage

• All four cookversion modes: 0x01000001 MONO, 0x01000002 STEREO, 0x01000003 JOINT_STEREO, 0x02000000 MC_COOK (5.1 / 7.1 layouts as chained 20-byte sub-blobs).
• All three sample-per-channel block sizes (256 / 512 / 1024).
• The full categoriser bisection (binary search + two-cursor expand / contract) with the 8-element expbits_tab cost vector.
• All seven SQVH tables (categories 0..6) with verbatim symbol orderings taken from the clean-room VLC tables sidecar at docs/audio/cook/data/cook-vlc-tables.md.
• All thirteen envelope Huffman tables and the five joint-stereo coupling tables.
• Sine-window MDCT lapping, per-slot gain ramps with the 2^((i-15)/gain_size_factor) gain table, deterministic AVLFG-derived dither (MD5-seeded, seed = 0).

Spec / docs

This decoder was implemented strictly from the clean-room behavioural-trace document at docs/audio/cook/cook-trace-reverse-engineering.md and its accompanying VLC tables at docs/audio/cook/data/cook-vlc-tables.md. No external library source code was consulted — ffmpeg(1) is used only as a black-box validator for fixture decoding.

Quick use

use oxideav_core::{CodecId, CodecParameters, Decoder, Packet, SampleFormat};

let mut params = CodecParameters::audio(CodecId::new(oxideav_cook::CODEC_ID_STR));
params.sample_rate = Some(44_100);
params.channels = Some(2);
params.sample_format = Some(SampleFormat::F32);
// extradata = the 8 / 16 / 80-byte cook-specific blob from the
// RealMedia MDPR chunk (see §4 of the trace doc).
params.extradata = vec![/* ... */];

let mut dec = oxideav_cook::decoder::make_decoder(&params).unwrap();
// dec.send_packet(&Packet { data: ..., pts: ..., .. })?;
// dec.receive_frame()?;

License

MIT. See LICENSE.