av/stream/flac/decode.go

63 lines
1.3 KiB
Go

package flac
import (
"bytes"
"errors"
"io"
"io/ioutil"
"github.com/go-audio/audio"
"github.com/go-audio/wav"
"github.com/mewkiz/flac"
"github.com/orcaman/writerseeker"
)
const wavAudioFormat = 1
// Decode takes a slice of flac and decodes to wav
func Decode(buf []byte) ([]byte, error) {
r := bytes.NewReader(buf)
stream, err := flac.Parse(r)
if err != nil {
return nil, errors.New("Could not parse FLAC")
}
ws := &writerseeker.WriterSeeker{}
enc := wav.NewEncoder(ws, int(stream.Info.SampleRate), int(stream.Info.BitsPerSample), int(stream.Info.NChannels), wavAudioFormat)
defer enc.Close()
var data []int
for {
// Decode FLAC audio samples.
frame, err := stream.ParseNext()
if err != nil {
if err == io.EOF {
break
}
return nil, err
}
// Encode WAV audio samples.
data = data[:0]
for i := 0; i < frame.Subframes[0].NSamples; i++ {
for _, subframe := range frame.Subframes {
data = append(data, int(subframe.Samples[i]))
}
}
buf := &audio.IntBuffer{
Format: &audio.Format{
NumChannels: int(stream.Info.NChannels),
SampleRate: int(stream.Info.SampleRate),
},
Data: data,
SourceBitDepth: int(stream.Info.BitsPerSample),
}
if err := enc.Write(buf); err != nil {
return nil, err
}
}
d, err := ioutil.ReadAll(ws.Reader())
if err != nil {
return nil, err
}
return d, nil
}