ace/lib/audiodriver/wavfifo.go

package audiodriver

import (
	"context"
	"encoding/binary"
	"io"
	"time"

	"github.com/pion/mediadevices/pkg/io/audio"
	"github.com/pion/mediadevices/pkg/prop"
	"github.com/pion/mediadevices/pkg/wave"
	"github.com/sirupsen/logrus"
)

const (
	DataChunkIDSize   = 4
	DataChunkSizeSize = 4
)

// BufferSize for pcm bytes
const BufferSize = 512
const BitsPerByte = 8

type WavFIFODriver struct {
	PCM        <-chan [BufferSize]byte
	WaveHeader <-chan *WavHeader
	closed     <-chan struct{}
	cancel     func()
}

func New() *WavFIFODriver {
	return &WavFIFODriver{}
}

func (w *WavFIFODriver) Open() error {
	defer logrus.Debug("device opened")
	ctx, cancel := context.WithCancel(context.Background())
	w.closed = ctx.Done()
	w.cancel = cancel

	return nil
}

func (w *WavFIFODriver) Close() error {
	defer w.cancel()
	return nil
}

func (w *WavFIFODriver) Properties() []prop.Media {
	waveHeader := <-w.WaveHeader
	logrus.Debugf("wave header: %v", waveHeader)
	return []prop.Media{
		{
			Audio: prop.Audio{
				SampleRate:    int(waveHeader.SampleRate),
				ChannelCount:  int(waveHeader.NumChannels),
				Latency:       waveHeader.GetLatnecy(),
				IsFloat:       false, // just 8bit or 16bit with qemu
				IsBigEndian:   false, // qemu should be little endian
				IsInterleaved: true,
			},
		},
	}
}

func (w *WavFIFODriver) AudioRecord(p prop.Media) (audio.Reader, error) {
	a := wave.NewInt16Interleaved(wave.ChunkInfo{
		Len:          BufferSize / int(p.SampleSize/BitsPerByte),
		Channels:     p.ChannelCount,
		SamplingRate: p.SampleRate,
	})

	reader := func() (wave.Audio, func(), error) {
		select {
		case <-w.closed:
			return nil, func() {}, io.EOF
		case pcmData, ok := <-w.PCM:
			logrus.Debug("got %d bytes pcm data", len(pcmData))
			if !ok {
				return nil, func() {}, io.ErrClosedPipe
			}
			copy(a.Data, bytesTo16BitSamples(pcmData[:]))
		case <-time.After(p.Latency):
		}
		return a, func() {}, nil
	}
	return audio.ReaderFunc(reader), nil
}

func bytesTo16BitSamples(b []byte) []int16 {
	samples := make([]int16, 0)
	for i := 0; i < len(b); i += 2 {
		sample := binary.LittleEndian.Uint16(b[i : i+1])
		samples = append(samples, int16(sample))
	}
	return samples
}