[Freeswitch-dev] Video synchronization

[Paulo Rogério Panhoto]

    I've found a way to synchronize the A/V streams with usleep() but I
don't think that's the best way to do this. Is there a switch_core....
function to perform a similar task (and maybe allow other tasks to run)?

    Here's the current version of the playback loop (that takes into
consideration multiple RTP packets per video frame) :

        u_int64_t videoNext = 0, audioNext = 0;
        u_int64_t ts = 0;
       
        bool videoSent = true, audioSent = true;
        while (switch_channel_ready(channel))
        {
            bool vOk, aOk;
            if(videoSent)
            {
                vid_frame.packetlen = vid_frame.buflen;
                vOk = vc.getVideoPacket(vid_frame.packet,
vid_frame.packetlen);
                if (vOk)
                {
                    switch_rtp_hdr_t *hdr =
reinterpret_cast<switch_rtp_hdr_t *>(vid_frame.packet);

                    videoNext =
vc.videoTrack().track.get90KTimestamp(ntohl(hdr->ts));
                    hdr->ts = htonl(videoNext);
                    if (pt)
                        hdr->pt = pt;
                }
                videoSent = false;
            }
            if(audioSent)
            {
                write_frame.datalen = write_frame.buflen;
                aOk = vc.getAudioPacket(write_frame.data,
write_frame.datalen);
                audioSent = false;
            }

            if (!vOk && !aOk)
                break;


            int64_t wait = min(audioNext, videoNext) - ts;
            if(wait > 0)
            {
                /* wait the time for the next A/V frame */
                usleep(wait * 1000 / 90);
                //switch_core_timer_next(&timer);
                ts += wait;
            }

            if (switch_channel_test_flag(channel, CF_VIDEO) && ts >=
videoNext)
            {
                switch_byte_t *data = (switch_byte_t *) vid_frame.packet;

                vid_frame.data = data + 12;
                vid_frame.datalen = vid_frame.packetlen - 12;
                switch_core_session_write_video_frame(session,
&vid_frame, SWITCH_IO_FLAG_NONE, 0);
                videoSent = true;
            }

            if(aOk && ts >= audioNext)
            {
                if (write_frame.datalen > (int) write_frame.buflen)
                    write_frame.datalen = write_frame.buflen;

                switch_core_session_write_frame(session, &write_frame,
SWITCH_IO_FLAG_NONE, 0);
                audioSent = true;
                audioNext += 90000 / 50; // 20ms
            }
        }

    Btw, thanks for the tip. I'll keep the separate thread to store
video for the record function.

    Regards,

    Paulo

On 13/07/10 15:39, Anthony Minessale wrote:
> we need to get nonblocking reads to the rtp working so the 
>
>   read_video_frame();
>    read_audio_frame();
>
> don't block when there is no data.

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