audio_decode library

Native Ogg Vorbis and MP3 decoding to raw PCM for Dart, backed by Sean Barrett's stb_vorbis and lieff's minimp3 over FFI.

The C decoders are compiled from source by a Dart build hook, so there is no prebuilt binary to ship and no platform plugin or system library to install beyond a C toolchain. Decoding runs in native code and copies the result into a Dart Int16List, so callers never manage native memory. The same code path runs in pure Dart (CLI, servers, tests) and in Flutter.

Decoding is deterministic for a given build, and the geometry it reports is the same everywhere. Sample values are not bit-identical across CPU architectures: the decoders compute in floating point, so around 0.03% of samples can differ by one least-significant bit between arm64 and x86-64. Do not compare checksums of decoded PCM across a mixed fleet.

This is a decoder, not a player: it turns encoded bytes into PCM samples for waveforms, analysis, resampling, machine-learning preprocessing, games and servers. For playback, pair it with a player package such as just_audio or flutter_sound. encodeWav writes the decoded PCM back out as a WAV file so the samples can be saved or handed to other tools.

import 'dart:io';
import 'package:audio_decode/audio_decode.dart';

void main() {
  final bytes = File('clip.mp3').readAsBytesSync();
  final pcm = decodeAudio(bytes);
  print('${pcm.sampleRate} Hz, ${pcm.channels} ch, ${pcm.duration}');
  File('clip.wav').writeAsBytesSync(encodeWav(pcm));
}

See decodeAudio, decodeOgg, decodeMp3, detectFormat, PcmAudio and encodeWav for the full API.

Classes

AudioInfo

An audio stream's geometry, read without decoding it to PCM.

PcmAudio

Decoded pulse-code-modulation audio: raw 16-bit samples plus their geometry.

Enums

AudioFormat

The container format of an encoded audio buffer, as identified by detectFormat.

Functions

audioInfo(Uint8List bytes) → AudioInfo

Reads bytes's geometry after sniffing its format with detectFormat, dispatching to oggInfo, mp3Info or wavInfo.

decodeAudio(Uint8List bytes) → PcmAudio

Decodes bytes after sniffing its format with detectFormat, dispatching to decodeOgg, decodeMp3 or decodeWav.

decodeMp3(Uint8List bytes) → PcmAudio

Decodes an MP3 stream to 16-bit PCM.

decodeOgg(Uint8List bytes) → PcmAudio

Decodes an Ogg Vorbis stream to 16-bit PCM.

decodeWav(Uint8List bytes) → PcmAudio

Decodes a RIFF/WAVE file holding uncompressed audio.

detectFormat(Uint8List bytes) → AudioFormat

Identifies the container format of bytes from its leading bytes.

encodeWav(PcmAudio audio) → Uint8List

Encodes audio as a canonical 16-bit PCM WAV (RIFF) file.

mp3Info(Uint8List bytes) → AudioInfo

Reads an MP3 stream's geometry without producing any audio.

oggInfo(Uint8List bytes) → AudioInfo

Reads an Ogg Vorbis stream's geometry without decoding any audio.

resample(PcmAudio audio, int targetRate) → PcmAudio

Resamples audio to targetRate, keeping its channel count.

toMono(PcmAudio audio) → PcmAudio

Mixes audio down to a single channel.

toSpeechPcm(PcmAudio audio, {int sampleRate = 16000}) → PcmAudio

Mono at 16 kHz, the input shape on-device speech models ask for.

wavInfo(Uint8List bytes) → AudioInfo

Reads a WAV file's geometry from its header, without decoding the samples.

Exceptions / Errors

AudioDecodeException

Thrown when decoding fails: the bytes are not valid audio of the expected format, or the native decoder rejected them.