Method readBufferAndAdd

internal/mux/mux.go:460–519

(buf []float32)

}

func (p *playerImpl) readBufferAndAdd(buf []float32) int {
	p.m.Lock()
	defer p.m.Unlock()

	if p.state != playerPlay {
		return 0
	}

	format := p.mux.format
	bitDepthInBytes := format.ByteLength()
	n := len(p.buf) / bitDepthInBytes
	if n > len(buf) {
		n = len(buf)
	}

	prevVolume := float32(p.prevVolume)
	volume := float32(p.volume)

	channelCount := p.mux.channelCount
	rateDenom := float32(n / channelCount)

	src := p.buf[:n*bitDepthInBytes]

	for i := 0; i < n; i++ {
		var v float32
		switch format {
		case FormatFloat32LE:
			v = math.Float32frombits(uint32(src[4*i]) | uint32(src[4*i+1])<<8 | uint32(src[4*i+2])<<16 | uint32(src[4*i+3])<<24)
		case FormatUnsignedInt8:
			v8 := src[i]
			v = float32(v8-(1<<7)) / (1 << 7)
		case FormatSignedInt16LE:
			v16 := int16(src[2*i]) | (int16(src[2*i+1]) << 8)
			v = float32(v16) / (1 << 15)
		default:
			panic(fmt.Sprintf("mux: unexpected format: %d", format))
		}
		if volume == prevVolume {
			buf[i] += v * volume
		} else {
			rate := float32(i/channelCount) / rateDenom
			if rate > 1 {
				rate = 1
			}
			buf[i] += v * (volume*rate + prevVolume*(1-rate))
		}
	}

	p.prevVolume = p.volume

	copy(p.buf, p.buf[n*bitDepthInBytes:])
	p.buf = p.buf[:len(p.buf)-n*bitDepthInBytes]

	if p.eof && len(p.buf) == 0 {
		p.returnBufferToPool()
		p.state = playerPaused
	}