rockbox-codecs

Audio decoding with Rockbox's codecs as a reusable Rust library.

The decoders are the Rockbox firmware codecs — the exact code that has played music on hundreds of DAP models for two decades — compiled into the crate by build.rs and driven through Rockbox's codec_api by a small C shim modeled on the upstream warble standalone test player. No external decoder libraries, no subprocess.

let mut dec = rockbox_codecs::Decoder::open("song.flac")?;
println!(
    "{} — {}",
    dec.metadata().artist,
    dec.metadata().title,
);
while let Some(chunk) = dec.next_chunk() {
    // chunk.pcm: interleaved stereo i16 at chunk.sample_rate Hz
    sink.write(&chunk.pcm);
}

Codecs (feature-gated)

All 29 codecs of Rockbox's static-link set (the same set the Android / WASM builds of rockboxd link) are available and enabled by default; disable default-features and pick what you need to trim compile time and binary size.

Feature	Formats	Decoder library	Verified by test
`flac`	FLAC	libffmpegFLAC	bit-exact roundtrip
`shorten`	Shorten (SHN)	libffmpegFLAC	compiles + table
`alac`	Apple Lossless (M4A)	libalac + libm4a	bit-exact roundtrip
`wavpack`	WavPack	libwavpack	bit-exact roundtrip
`ape`	Monkey's Audio (APE)	libdemac	compiles + table
`tta`	True Audio	libtta	bit-exact roundtrip
`wav`	WAV (PCM + ADPCM family)	libpcm	bit-exact roundtrip
`aiff`	AIFF	libpcm	bit-exact roundtrip
`au`	Sun AU / SND	libpcm	bit-exact roundtrip
`wav64`	Sony Wave64	libpcm	bit-exact roundtrip
`smaf`	SMAF (Yamaha mobile)	libpcm	compiles + table
`vox`	Dialogic VOX ADPCM	libpcm	compiles + table
`mpa`	MP1 / MP2 / MP3 (incl. MP3-in-ASF)	libmad + libasf	decode + energy check
`vorbis`	Ogg Vorbis	libtremor	decode + energy check
`aac`	AAC / HE-AAC (M4A)	libfaad + libm4a	decode + energy check
`aac_bsf`	raw AAC / ADTS streams	libfaad	decode + energy check
`opus`	Opus	libopus (fixed point)	decode + energy check
`mpc`	Musepack SV7 / SV8	libmusepack	compiles + table
`speex`	Ogg Speex	libspeex	compiles + table
`wma`	WMA v1/v2 in ASF	libwma + libasf	decode + energy check
`wmapro`	WMA Professional	libwmapro + libasf	compiles + table
`a52`	AC3 / A-52	liba52	decode + energy check
`a52_rm`	AC3 in RealMedia	liba52 + librm	compiles + table
`cook`	RealAudio Cook	libcook + librm	compiles + table
`raac`	AAC in RealMedia	libfaad + librm	compiles + table
`atrac3_rm`	ATRAC3 in RealMedia	libatrac + librm	compiles + table
`atrac3_oma`	ATRAC3 in Sony OMA	libatrac	compiles + table
`adx`	CRI ADX (game audio)	built-in	decode + energy check
`mod`	Amiga MOD	built-in	compiles + table

Not included: the libgme chiptune family (NSF, GBS, HES, KSS, AY, SGC, VGM, VTX), SPC, SID and SAP — their emulator cores share symbols across codecs and only work in Rockbox's dlopen-one-codec-at-a-time model, so the upstream static builds exclude them too.

API model

[Decoder::open] parses metadata (via the sibling rockbox-metadata crate, re-exported as Metadata), selects the codec by format, and starts a dedicated decode thread.
[Decoder::next_chunk] pulls interleaved stereo i16 PCM through a bounded channel (backpressure keeps memory flat). Mono sources are duplicated to stereo; high-depth codecs are converted from their native fraction-bit format.
[Decoder::seek] / [Decoder::elapsed] map to the codec's native seek handling (sample-accurate where the codec supports it).
chunk.sample_rate is the codec's output rate — Opus always decodes at 48 kHz, everything else at the file's native rate. Pair with rockbox-dsp for resampling, EQ and ReplayGain.

One session at a time: Rockbox codecs share a single global codec_api instance, so Decoder::open blocks until any other live Decoder in the process is dropped.

How it's built

Each codec (wrapper + codec_crt0.c + its decoder library) compiles in its own cc build with the four entry symbols renamed per codec (-D__header=__header_<name>, …) — the same compile-time scheme the Rockbox WASM build uses, so no objcopy is needed on any platform.
A static codec table maps formats to the renamed __header_<name> entry points (the pattern of Rockbox's Android static-codec loader).
codeclib (shared helpers), libm4a (shared by alac + aac), tlsf (allocator for the ogg codecs) and libasf (MP3-in-ASF) compile once.
libopus and libtremor both bundle libogg's framing.c with identical symbol names but different internals; the opus copy is prefix-renamed (opus_ogg_*) so both codecs can coexist in one binary.
In-repo builds compile from the live lib/rbcodec tree; the published package builds from the vendor/ snapshot (./sync-vendor.sh).

Examples

# Player CLI: Rockbox decode → cpal output
cargo run --example play -- ~/Music/track.m4a

Caveats