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package wav
// #define DR_WAV_IMPLEMENTATION
// #include "dr_wav.h"
import "C"
import (
"fmt"
"sync"
"github.com/op/go-logging"
"layeh.com/gopus"
)
// number of individual samples per channel per batch
const samplesPerChannelPerBatch = 1920
var log = logging.MustGetLogger("wav")
type Wav struct {
filename *C.char
enc *gopus.Encoder
wav *C.drwav
once sync.Once
Done <-chan struct{}
done chan<- struct{}
}
func New(filename string) (*Wav, error) {
cfname := C.CString(filename)
wav := C.drwav_open_file(cfname)
if wav == nil {
C.drwav_close(wav)
return nil, fmt.Errorf("Unable to initialize drwav.")
}
if int(wav.channels) != 2 {
C.drwav_close(wav)
return nil, fmt.Errorf("Wrong number of channels!")
}
if int(wav.sampleRate) != 48000 {
C.drwav_close(wav)
return nil, fmt.Errorf("Wrong sample rate.")
}
enc, err := gopus.NewEncoder(int(wav.sampleRate), int(wav.channels), gopus.Audio)
if err != nil {
C.drwav_close(wav)
return nil, err
}
done := make(chan struct{}, 1)
return &Wav{
filename: C.CString(filename),
enc: enc,
wav: wav,
done: done,
Done: done,
}, nil
}
func (w *Wav) Stop() {
w.once.Do(func() {
close(w.done)
})
}
func (w *Wav) Start(ch chan<- []byte) {
go func() {
defer w.Stop()
samplesPerBatch := samplesPerChannelPerBatch * int(w.wav.channels)
batchSize := samplesPerBatch * int(w.wav.bytesPerSample)
buf := C.malloc(C.size_t(batchSize))
defer C.free(buf)
defer C.drwav_close(w.wav)
elems := make([]int16, samplesPerBatch)
idx := 0
for i := 0; i*samplesPerBatch <= int(w.wav.totalSampleCount); i += 1 {
readSamples := C.drwav_read_s16(w.wav, C.dr_uint64(samplesPerBatch), (*C.dr_int16)(buf))
slc := (*[1 << 30]int16)(buf)[:readSamples:readSamples]
readIdx := 0
for {
batchSamplesToFill := samplesPerBatch - idx
readSamplesRemaining := int(readSamples) - readIdx
// break if we don't have enough samples to fill the rest of the buffer
if readSamplesRemaining < batchSamplesToFill {
break
}
copy(elems[idx:], slc[readIdx:readIdx+batchSamplesToFill])
idx = 0
readIdx += batchSamplesToFill
b, err := processPCM(w.wav, w.enc, elems[:])
if err != nil {
log.Errorf("error encoding pcm: %q", err)
continue
}
select {
case <-w.Done:
return
default:
}
select {
case <-w.Done:
return
case ch <- b:
}
}
batchSamplesToFill := samplesPerBatch - idx
readSamplesRemaining := int(readSamples) - readIdx
if readSamplesRemaining >= batchSamplesToFill {
log.Fatalf("Had enough samples to fill batch after for loop.")
}
copy(elems[idx:], slc)
idx += len(slc)
if int(readSamples) < samplesPerBatch {
break
}
}
}()
}
func processPCM(wav *C.drwav, enc *gopus.Encoder, data []int16) ([]byte, error) {
return enc.Encode(data, len(data)/int(wav.channels), len(data)*2)
}
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