2019-01-21 08:11:49 +03:00
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package flac
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import (
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"bytes"
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"errors"
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"io"
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"github.com/go-audio/audio"
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"github.com/go-audio/wav"
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"github.com/mewkiz/flac"
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)
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const wavAudioFormat = 1
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type buffer struct {
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Buffer bytes.Buffer
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Index int64
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}
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func (b *buffer) Bytes() []byte {
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return b.Buffer.Bytes()
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}
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func (b *buffer) Read(p []byte) (int, error) {
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n, err := bytes.NewBuffer(b.Buffer.Bytes()[b.Index:]).Read(p)
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if err == nil {
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if b.Index+int64(len(p)) < int64(b.Buffer.Len()) {
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b.Index += int64(len(p))
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} else {
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b.Index = int64(b.Buffer.Len())
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}
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}
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return n, err
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}
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func (b *buffer) Write(p []byte) (int, error) {
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n, err := b.Buffer.Write(p)
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if err == nil {
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b.Index = int64(b.Buffer.Len())
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}
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return n, err
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}
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func (b *buffer) Seek(offset int64, whence int) (int64, error) {
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var err error
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var Index int64 = 0
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switch whence {
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case 0:
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if offset >= int64(b.Buffer.Len()) || offset < 0 {
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err = errors.New("Invalid Offset.")
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} else {
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b.Index = offset
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Index = offset
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}
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default:
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err = errors.New("Unsupported Seek Method.")
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}
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return Index, err
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}
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// Decode takes a slice of flac and decodes to wav
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func Decode(buf []byte) ([]byte, error) {
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r := bytes.NewReader(buf)
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stream, err := flac.Parse(r)
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if err != nil {
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return nil, errors.New("Could not parse FLAC")
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}
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fb := &buffer{}
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enc := wav.NewEncoder(fb, int(stream.Info.SampleRate), int(stream.Info.BitsPerSample), int(stream.Info.NChannels), wavAudioFormat)
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defer enc.Close()
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var data []int
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for {
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// Decode FLAC audio samples.
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frame, err := stream.ParseNext()
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if err != nil {
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if err == io.EOF {
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break
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}
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return nil, err
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}
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// Encode WAV audio samples.
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data = data[:0]
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for i := 0; i < frame.Subframes[0].NSamples; i++ {
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for _, subframe := range frame.Subframes {
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data = append(data, int(subframe.Samples[i]))
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}
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}
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buf := &audio.IntBuffer{
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Format: &audio.Format{
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NumChannels: int(stream.Info.NChannels),
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SampleRate: int(stream.Info.SampleRate),
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},
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Data: data,
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SourceBitDepth: int(stream.Info.BitsPerSample),
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}
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if err := enc.Write(buf); err != nil {
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return nil, err
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}
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}
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return fb.Bytes(), nil
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}
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