//Seek to the keyframe at timestamp.
func (s *Context) AvSeekFrame(st int, t int64, f int) int {
return int(C.av_seek_frame((*C.struct_AVFormatContext)(s), C.int(st), C.int64_t(t), C.int(f)))
}
func (self *Decoder) Start(videoStream, audioStream *C.AVStream,
scaleWidth, scaleHeight C.int) *Decoder {
self.running = true
self.duration = time.Duration(self.FormatContext.duration * C.AV_TIME_BASE / 1000)
vCodecCtx := videoStream.codec
aCodecCtx := audioStream.codec
self.durationPerSample = time.Second / time.Duration(aCodecCtx.sample_rate)
// frame pool
poolSize := 16
pool := make(chan *C.AVFrame, poolSize)
self.pool = pool
numBytes := C.size_t(C.avpicture_get_size(C.PIX_FMT_YUV420P, scaleWidth, scaleHeight))
for i := 0; i < poolSize; i++ {
frame := C.av_frame_alloc()
self.frames = append(self.frames, frame)
buffer := (*C.uint8_t)(unsafe.Pointer(C.av_malloc(numBytes)))
self.buffers = append(self.buffers, buffer)
C.avpicture_fill((*C.AVPicture)(unsafe.Pointer(frame)), buffer, C.PIX_FMT_YUV420P,
scaleWidth, scaleHeight)
pool <- frame
}
// decode
self.frameChan = make(chan *C.AVFrame, 512)
go func() {
runtime.LockOSThread()
// scale context
scaleContext := C.sws_getCachedContext(nil, vCodecCtx.width, vCodecCtx.height, vCodecCtx.pix_fmt,
scaleWidth, scaleHeight, C.PIX_FMT_YUV420P, C.SWS_LANCZOS, nil, nil, nil)
if scaleContext == nil {
log.Fatal("get scale context failed")
}
// resample context
resampleContext := C.swr_alloc_set_opts(nil,
C.AV_CH_LAYOUT_STEREO, C.AV_SAMPLE_FMT_FLT, aCodecCtx.sample_rate,
C.int64_t(aCodecCtx.channel_layout), aCodecCtx.sample_fmt, aCodecCtx.sample_rate,
0, nil)
if resampleContext == nil {
log.Fatal("get resample context failed")
}
C.swr_init(resampleContext)
var packet C.AVPacket
var frameFinished C.int
var pts int64
var packetTime time.Duration
vFrame := C.av_frame_alloc()
aFrame := C.av_frame_alloc()
videoIndex := videoStream.index
audioIndex := audioStream.index
resampleBuffer := (*C.uint8_t)(C.av_malloc(4096 * 8))
resampleBufferp := &resampleBuffer
self.Timer = NewTimer()
// decode
for self.running {
// seek
if self.seekTarget > 0 {
if C.av_seek_frame(self.FormatContext, -1,
C.int64_t(float64(self.seekNext)/float64(time.Second)*float64(C.AV_TIME_BASE)),
C.AVSEEK_FLAG_BACKWARD) < 0 {
log.Fatal("seek error")
}
for _, codecCtx := range self.openedCodecs {
C.avcodec_flush_buffers(codecCtx)
}
p("frame seek done\n")
}
read_packet:
// read packet
C.av_free_packet(&packet)
if C.av_read_frame(self.FormatContext, &packet) < 0 { // read packet
log.Fatal("read frame error") //TODO stop gracefully
}
// get packet time
if packet.dts != C.AV_NOPTS_VALUE {
pts = int64(packet.dts)
} else {
pts = 0
}
if packet.stream_index == videoIndex {
packetTime = time.Duration(float64(pts) * float64(C.av_q2d(videoStream.time_base)) * float64(time.Second))
} else if packet.stream_index == audioIndex {
packetTime = time.Duration(float64(pts) * float64(C.av_q2d(audioStream.time_base)) * float64(time.Second))
} else { // ignore packet
goto read_packet
}
p("packet time %v at timer time %v\n", packetTime, self.Timer.Now())
// check seek
if self.seekTarget > 0 && packetTime > 0 { // if packet time cannot determined, skip
if packetTime < self.seekTarget { // seek again
self.seekNext += self.seekStep
p("seek again %v\n", self.seekNext)
} else { // seek ok
p("seek ok\n")
self.seekTarget = 0
self.Timer.Jump(packetTime - self.Timer.Now())
}
}
// decode
if packet.stream_index == videoIndex { // decode video
if C.avcodec_decode_video2(vCodecCtx, vFrame, &frameFinished, &packet) < 0 {
continue // bad packet
}
if frameFinished <= 0 {
goto read_packet // frame not complete
}
bufFrame := <-pool // get frame buffer
C.sws_scale(scaleContext, // scale
&vFrame.data[0], &vFrame.linesize[0], 0, vCodecCtx.height,
&bufFrame.data[0], &bufFrame.linesize[0])
bufFrame.pts = C.int64_t(packetTime) // set packet time
self.frameChan <- bufFrame // push to queue
p("video frame %v\n", packetTime)
} else if packet.stream_index == audioIndex { // decode audio
decode_audio_packet:
l := C.avcodec_decode_audio4(aCodecCtx, aFrame, &frameFinished, &packet)
if l < 0 {
continue // bad packet
}
if frameFinished <= 0 {
goto read_packet // frame not complete
}
if frameFinished > 0 { // frame finished
n := C.swr_convert(resampleContext, resampleBufferp, 4096,
aFrame.extended_data, aFrame.nb_samples)
if n != aFrame.nb_samples {
log.Fatal("audio resample failed")
}
self.audioFrames <- &AudioFrame{
time: packetTime,
data: C.GoBytes(unsafe.Pointer(resampleBuffer), n*8),
}
}
if l != packet.size { // multiple frame packet
packet.size -= l
packet.data = (*C.uint8_t)(unsafe.Pointer(uintptr(unsafe.Pointer(packet.data)) + uintptr(l)))
goto decode_audio_packet
}
p("audio frame %v\n", packetTime)
} else { // other stream
goto read_packet
}
}
}()
// sync video
go func() {
maxDelta := (time.Second / time.Duration(C.av_q2d(videoStream.r_frame_rate)/10))
for frame := range self.frameChan {
delta := time.Duration(frame.pts) - self.Timer.Now()
p("video frame %v, delta %v, max delta %v\n", time.Duration(frame.pts), delta, maxDelta)
if delta > 0 {
if delta > maxDelta {
self.Timer.Jump(delta)
print("timer jumped\n")
} else {
time.Sleep(delta)
}
} else if delta < 0 { // drop frame
self.RecycleFrame(frame)
continue
}
self.timedFrames <- frame
}
}()
return self
}