opusgo

This is a pure go implementation of an Ogg/Opus parser, decoder, and encoder. It was produced by transpiling the libopus C sources to Go using ccgo, as well as using GPT 5.2 help. No cgo is used.

Directory structure:

• cmd/oggopusdump: command-line tool to dump Ogg/Opus headers and packet sizes
• cmd/oggopusextract: command-line tool to extract Opus audio packets
• cmd/oggopus2wav: command-line tool to decode Ogg/Opus
• cmd/wav2oggopus: command-line tool to encode WAV to Ogg/Opus
• ogg - Parser for the Ogg format and Opus packet reader
• opus - Encoder and decoder opus API
• opuscc - Transpiled libopus C source of the decoder logic
• opusccenc - Transpiled libopus C source of the encoder logic
• libcshim - Small libc shim for the transpiled C code, replaces some modernc.org/libc functionality
• examples - Example programs using the library

Minimal high level API example

Decoding an opus file to get PCM samples. Note the sample rate of the PCM data is always 48000 Hz.

player, _ := opusgo.NewPlayerFromFile("file.opus", true) // true means stream from disk
data := make([]byte, 48000*2*2) // 1 second buffer for stereo s16le
io.ReadFull(player, data)
// data now contains PCM samples

Minimal low level API example

Decoding an opus file to get PCM samples. Note the sample rate of the PCM data is always 48000 Hz.

// error handling omitted for brevity
input, _ := os.Open("file.opus")
reader, _ := ogg.NewOpusReader(input) // input can be any io.Reader
decoder, _ := opus.NewDecoderFromHead(reader.Head)
for {
  packet, err := reader.ReadAudioPacket()
  if err != nil {
    // no more audio packets
    break
  }
  decoded, n, _ := decoder.DecodePacket(packet, nil) // nil can instead be a pre-allocated []int16, otherwise new memory is allocated
  // decoded is an []int16 PCM audio buffer with n samples per channel, so total samples = n * reader.Head.Channels
  // use decoded PCM samples...
}

Example program usage

From this folder:

• Dump headers + packet sizes:

go run ./cmd/oggopusdump --no-crc path/to/file.ogg

• Extract length-prefixed audio packets:

go run ./cmd/oggopusextract --out packets.bin path/to/file.ogg

packets.bin format: repeating (u32le length, length bytes packet).

• Decode .opus to .wav (48kHz s16le):

go run ./cmd/oggopus2wav --out out.wav path/to/file.opus

• Profile decoding:

go run ./cmd/oggopus2wav --cpuprofile cpu.pprof --out out.wav path/to/file.opus
go tool pprof -top cpu.pprof

• Encoding .wav to .opus:

go run ./cmd/wav2oggopus --bitrate 64000 --out out.opus path/to/file.wav