示例#1
0
// Decode decodes Ogg/Vorbis data to playable stream.
//
// Sample rate is automatically adjusted to fit with the audio context.
func Decode(context *audio.Context, src audio.ReadSeekCloser) (*Stream, error) {
	decoded, channelNum, sampleRate, err := decode(src)
	if err != nil {
		return nil, err
	}
	if channelNum != 1 && channelNum != 2 {
		return nil, fmt.Errorf("vorbis: number of channels must be 1 or 2 but was %d", channelNum)
	}
	var s audio.ReadSeekCloser = decoded
	size := decoded.Size()
	if channelNum == 1 {
		s = convert.NewStereo16(s, true, false)
		size *= 2
	}
	if sampleRate != context.SampleRate() {
		s = convert.NewResampling(s, size, sampleRate, context.SampleRate())
		size = size * int64(context.SampleRate()) / int64(sampleRate)
	}
	return &Stream{s, size}, nil
}
示例#2
0
// Decode decodes WAV (RIFF) data to playable stream.
//
// The format must be 1 or 2 channels, 8bit or 16bit little endian PCM.
// The format is converted into 2 channels and 16bit.
//
// Sample rate is automatically adjusted to fit with the audio context.
func Decode(context *audio.Context, src audio.ReadSeekCloser) (*Stream, error) {
	buf := make([]byte, 12)
	n, err := io.ReadFull(src, buf)
	if n != len(buf) {
		return nil, fmt.Errorf("wav: invalid header")
	}
	if err != nil {
		return nil, err
	}
	if !bytes.Equal(buf[0:4], []byte("RIFF")) {
		return nil, fmt.Errorf("wav: invalid header: 'RIFF' not found")
	}
	if !bytes.Equal(buf[8:12], []byte("WAVE")) {
		return nil, fmt.Errorf("wav: invalid header: 'WAVE' not found")
	}

	// Read chunks
	dataSize := int64(0)
	headerSize := int64(0)
	sampleRateFrom := 0
	sampleRateTo := 0
	mono := false
	bitsPerSample := 0
chunks:
	for {
		buf := make([]byte, 8)
		n, err := io.ReadFull(src, buf)
		if n != len(buf) {
			return nil, fmt.Errorf("wav: invalid header")
		}
		if err != nil {
			return nil, err
		}
		headerSize += 8
		size := int64(buf[4]) | int64(buf[5])<<8 | int64(buf[6])<<16 | int64(buf[7])<<24
		switch {
		case bytes.Equal(buf[0:4], []byte("fmt ")):
			// Size of 'fmt' header is usually 16, but can be more than 16.
			if size < 16 {
				return nil, fmt.Errorf("wav: invalid header: maybe non-PCM file?")
			}
			buf := make([]byte, size)
			n, err := io.ReadFull(src, buf)
			if n != len(buf) {
				return nil, fmt.Errorf("wav: invalid header")
			}
			if err != nil {
				return nil, err
			}
			format := int(buf[0]) | int(buf[1])<<8
			if format != 1 {
				return nil, fmt.Errorf("wav: format must be linear PCM")
			}
			channelNum := int(buf[2]) | int(buf[3])<<8
			switch channelNum {
			case 1:
				mono = true
			case 2:
				mono = false
			default:
				return nil, fmt.Errorf("wav: channel num must be 1 or 2 but was %d", channelNum)
			}
			bitsPerSample = int(buf[14]) | int(buf[15])<<8
			if bitsPerSample != 8 && bitsPerSample != 16 {
				return nil, fmt.Errorf("wav: bits per sample must be 8 or 16 but was %d", bitsPerSample)
			}
			sampleRate := int64(buf[4]) | int64(buf[5])<<8 | int64(buf[6])<<16 | int64(buf[7])<<24
			if int64(context.SampleRate()) != sampleRate {
				sampleRateFrom = int(sampleRate)
				sampleRateTo = context.SampleRate()
			}
			headerSize += size
		case bytes.Equal(buf[0:4], []byte("data")):
			dataSize = size
			break chunks
		default:
			buf := make([]byte, size)
			n, err := io.ReadFull(src, buf)
			if n != len(buf) {
				return nil, fmt.Errorf("wav: invalid header")
			}
			if err != nil {
				return nil, err
			}
			headerSize += size
		}
	}
	var s audio.ReadSeekCloser = &stream{
		src:        src,
		headerSize: headerSize,
		dataSize:   dataSize,
		remaining:  dataSize,
	}
	if mono || bitsPerSample != 16 {
		s = convert.NewStereo16(s, mono, bitsPerSample != 16)
		if mono {
			dataSize *= 2
		}
		if bitsPerSample != 16 {
			dataSize *= 2
		}
	}
	if sampleRateFrom != sampleRateTo {
		s = convert.NewResampling(s, dataSize, sampleRateFrom, sampleRateTo)
		dataSize = dataSize * int64(sampleRateTo) / int64(sampleRateFrom)
	}
	return &Stream{s, dataSize}, nil
}