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• Setting up time triggers on video player

  28 juillet 2022, par gPats

  Background :

  



  I have a some text that I want to display in a textbox whenever the video is playing in a certain interval, say (00:02:00-00:04:00 "Hello there").

  



  These textbox should only be displayed whenever the video is playing in the particular interval. If I rewind, or skip the video to a different time, the textbox should be generated/destroyed depending whether the current time falls within the interval or not.

  



  I have searched the documentation for ffplay and vlc for implementing this functionality.

  



  What I have tried :

  



  ffplay : my strategy would be to keep polling the current time of the video which ffplay dumps in STDERR and check if the current time falls within the interval.

  



  LibVLC :
LibVLC supports asynchronous events, but not the kind which would depend on the time at which video is playing.

  



  My question :

  



  1.Is it advisable to keep polling the current video time or setup callbacks/trigger functions ?

  



  2.Is it possible to get the current playing time of the video as a variable and create callback functions accordingly ?

  



  NOTE : I am aware that subtitles do the same thing, however I want the text to be in a different window. The textbox should be decoupled from the video player I use.

  


• ffmpeg H264 Encode Frame at a time for network streaming

  4 février 2017, par Richard Harrow

  I’m working on a remote desktop application, I would like to send an encoded H264 packet over TCP by using ffmpeg for the encoding. However I couldn’t find useful info for the particular case of encoding just one frame (already on YUV444) and get the packet.

  I have several issues, the first was that :

  avcodec_encode_video2

  Was not blocking, I found that most of the time you get the "delayed" frames at the end, however, since this is a real time streaming the solution was :

  av_opt_set(mCodecContext->priv_data, "tune", "zerolatency", 0);

  Now I got the frame, but several issues, it takes a while and even worse I got a gray with trash pixels video as result. My configuration for the Codec Context :

   m_pCodecCtx->bit_rate=8000000;
  
  m_pCodecCtx->codec_id=AV_CODEC_ID_H264;
  
  m_pCodecCtx->codec_type = AVMEDIA_TYPE_VIDEO;
  
  m_pCodecCtx->width=1920;
  
  m_pCodecCtx->height=1080;
  
  m_pCodecCtx->pix_fmt=AV_PIX_FMT_YUV444P;
  
  m_pCodecCtx->time_base.num = 1;
  
  m_pCodecCtx->time_base.den = 25;
  
  m_pCodecCtx->gop_size = 1;
  
  m_pCodecCtx->keyint_min = 1;
  
  m_pCodecCtx->i_quant_factor = float(0.71);
  
  m_pCodecCtx->b_frame_strategy = 20;
  
  m_pCodecCtx->qcompress = (float)0.6;
  
  m_pCodecCtx->qmax = 51;
  
  m_pCodecCtx->qmin = 20;
  
  m_pCodecCtx->max_qdiff = 4;
  
  m_pCodecCtx->refs = 4;
  
  m_pCodecCtx->max_b_frames = 1;
  
  m_pCodecCtx->thread_count = 1;

  I would like to know how this could be done, how do I set the "I Frames" ? and, that would be the optimal for a "one at a time" encoding ? Also I’m not concerned right now with the quality, just need to be fast enough (under 16 ms).

  For the encoding part :

  nres = avcodec_encode_video2(m_pCodecCtx,&packet,m_pFrame,&framefinished);
  
  
  
  if(nres<0){
  
      qDebug() << "error encoding: " << nres << endl;
  
  }
  
  
  
  if(framefinished){
  
      m_pFrame->pts++;
  
       ofstream vidout("video.h264",ios::app);
  
       if(vidout.good()){
  
           vidout.write((const char*)&packet.data[0],packet.size);
  
       }
  
       vidout.close();
  
  
  
       av_packet_unref(&packet);
  
  
  
  }

  I’m not using a container, just a raw file, ffplay reproduce raw files if the packets are right, and that’s my principal issue. I’m planning to send the packet over tcp and decode on the client. Any help would be greatly appreciated.

• How to add current UTC Time in MKV file metadata using ffmpeg ?

  1er mai 2022, par Shahpari

  I am not sure if it's possible, but is there anyway we can add current UTC time inside the mkv metatag using ffmpeg ? i read https://wiki.multimedia.cx/index.php?title=FFmpeg_Metadata but i could not find anything.

  


  -metadata "Creation Time"="Need to add time tag/code"


  


  output will show

  


  Creation Time: UTC 2020-06-04 02:40:29