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• Why android video player that based on ffmpeg can't sync video' time and audio's time ?

  6 juillet 2021, par ZSpirytus

  Background

  


  Recently, I use ffmpeg to write my first Android video player. But video channel's time is faster than audio channel's time about 2 3 times.

  


  Question

  


  Why android video player audio and video is out of sync ? Video is about faster than audio 2 3 times. Thanks for your reading and answers.

  


  Code

  


  In short, I use PacketDispatcher to read AVPacket from http hlv source :

  


  void PacketDispatcher::RealDispatch() {
    while (GetStatus() != DISPATCHER_STOP) {
        ...

        AVPacket *av_packet = av_packet_alloc();
        int ret = av_read_frame(av_format_context, av_packet);

        // PacketDispatcher is who read the AVPacket from http hlv source 
        // and dispatch to decoder by its stream index.
        decoder_map[av_packet->stream_index]->Push(av_packet);
    }
}


  


  And then, Decoder written by Producer-Consumer Pattern, Decoder maintain a queue that store all the AVPacket received from PacketDispatcher. The code like this :

  


  // write to the queue
void BaseDecoder::Push(AVPacket *av_packet) {
    ...
    av_packet_queue.push(av_packet);
    ...
}

// real decode logic
void BaseDecoder::RealDecode() {
    ...
    while (true) {
        // read frame from codec
        AVFrame *av_frame = av_frame_alloc();
        ret = avcodec_receive_frame(av_codec_ctx, av_frame);

        void *decode_result = DecodeFrame(av_frame);
        // send to render
        m_render->Render(decode_result);
    }
}


  


  And then, I do rendering logic in Render. Render also written by Producer-Consumer Pattern, it maintain a queue that store AVFrame received from Decoder, the code like this :

  


  // write AVFrame
void BaseRender::Render(void *frame_data) {
    ...
    frame_queue.push(frame_data);
    ...
}

// render to surface or Open SL
void BaseRender::RealRender() {
    if (m_render_synchronizer && m_render_synchronizer->Sync(frame_data)) {
        continue;
    }
}


  


  Finally, the synchronizer will decide to sleep time or drop video frame according to the frame pts, frame pts is :

  


  frame_data->pts = av_frame->best_effort_timestamp * av_q2d(GetTimeBase());


  


  Also, video extra delay is :

  


  frame_data->video_extra_delay = av_frame->repeat_pict * 1.0 / fps * 2.0;


  


  RenderSynchronizer code like this :

  


  bool RenderSynchronizer::Sync(void *frame_data) {&#xA;    auto base_frame_data = static_cast<baseframedata>(frame_data);&#xA;    if (base_frame_data->media_type == AVMEDIA_TYPE_AUDIO) {&#xA;        audio_pts = pcm_data->pts;&#xA;        return false;&#xA;    } else if (base_frame_data->media_type == AVMEDIA_TYPE_VIDEO) {&#xA;        video_pts = rgba_data->pts;&#xA;        return ReceiveVideoFrame(static_cast<rgbadata>(frame_data));&#xA;    }&#xA;    return false;&#xA;}&#xA;&#xA;bool RenderSynchronizer::ReceiveVideoFrame(RGBAData *rgba_data) {&#xA;    if (audio_pts &lt;= 0 || video_pts &lt;= 0) {&#xA;        return false;&#xA;    }&#xA;&#xA;    double diff = video_pts - audio_pts;&#xA;    if (diff > 0) {&#xA;        if (diff > 1) {&#xA;            av_usleep((unsigned int) (rgba_data->extra_delay * 1000000.0));&#xA;        } else {&#xA;            av_usleep((unsigned int) ((diff &#x2B; rgba_data->extra_delay) * 1000000.0));&#xA;        }&#xA;        return false;&#xA;    } else if (diff &lt; 0) {&#xA;        LOGD(TAG, "drop video frame");&#xA;        return true;&#xA;    } else {&#xA;        return false;&#xA;    }&#xA;}&#xA;</rgbadata></baseframedata>

  


• Revision b04d766800 : Use small transform size in non-rd real-time mode In non-rd real-time mode, cho

  30 mai 2014, par Yunqing Wang

  Changed Paths :
   Modify /vp9/encoder/vp9_encodeframe.c

  
   Modify /vp9/encoder/vp9_speed_features.c

  
   Modify /vp9/encoder/vp9_speed_features.h

  
  
  Use small transform size in non-rd real-time mode

  In non-rd real-time mode, choosing smaller transform size in
  encoding gives better video quality and good speed gain than
  choosing larger transform size. This patch set tx size search
  method to ALLOW_8X8, which is better than using 4x4 or other
  larger sizes.

  Borg tests on rtc set at speed 6 showed significant gain on quality.
  PSNR gain : 11.034% and SSIM gain : 15.466%.

  The speed gain is 5% - 12% for <720p clips, and 2% - 7% for
  720p clips.

  Change-Id : If4dc74ed2df359346b059f47fb73b4a0193ec548

• how to play edited videos in mvp

  19 avril 2021, par Eswar T

  how to play edited videos(before exporting them) like how we can play in ffplay like here an example in ffplay so can we also play them using MVP if yes please convert this command thank you

  &#xA;

  ffplay -i 1.mp4 -ss 00:00:30.100 -t 00:00:10 -af volume=2.0,atempo=2.0-vf transpose=0,transpose=0,setpts=1/0.5*PTS,fps=30) 


  &#xA;

  and using a playlist how can we play multiple edited files like

  &#xA;

  ffplay -i 1.mp4 -ss 00:00:30.100 -t 00:00:10 -af volume=2.0,atempo=2.0-vf transpose=0,transpose=0,setpts=1/0.5*PTS,fps=30) && ffplay -i 2.mp4 -ss 00:00:30.100 -t 00:00:10 -af volume=2.0,atempo=2.0-vf transpose=0,transpose=0,setpts=1/0.5*PTS,fps=30)


  &#xA;

  thank you

  &#xA;