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• Input transparent motions into FFMPEG pipe:0

  29 septembre 2021, par NTPHCM

  I follow this to bring a stdinput to FFMPEG.

  


  The idea is : we use AS3 to capture every frame in Animate to byteArray (with ARGB pixel format - means the frame can have transparancy background). After that, we transfer that byteArray to FFMPEG to get output.

  


  If I capture non-transparency picture (the picture with background), the process works well to create motion video.

  


  But when I capture transparency picture and make motion (multi-frame video), the problem appears as below :
Output picture

  


  We can see the bird print a long streak, but I expect one bird flying from the right to the left like this.

  


  It seems like the previous frames are not cleared. Do you have any suggestions to solve this ?

  


• How to combine a .mp4 video with a .wav audio with an offset in ffmpeg from command line ?

  15 mars 2014, par minder42

  I've got a TV clip in mp4 format containing audio and video, and an WAV audio_commentary track.

  I've been trying to combine them in ffmpeg and then play it online with a flash player (which can only take h264 format)

  What's the best ffmpeg command to accomplish this ? My inputs are MP4 video, WAV audio, and an offset in seconds, the time the audio commentary starts relative to the start of the mp4 video.

  I tried

  ffmpeg -i input_audio.wav -i input_vid.mp4 -vcodec copy output.mp4

  and

  ffmpeg -vcodec copy -ss offset -i input_audio.wav -i input_video.mp4 output.mp4

  nether of these do what I want and output the video in the h264 format that is good for flash players- Is there a way to do this from command line in ffmpeg ?

• How to write a video stream containing B-frame and no DTS to a MP4 container ?

  14 février 2020, par SteveH

  I want to save a h264 video stream received from a RTSP source to a MP4 container.
  Not like other questions asked on SO, here the challenges I face are :

  • The stream contains B frames.

  • The stream has only PTS given by the RTP/RTCP.

  Here is the code I did

  //  ffmpeg
  
      pkt->data = ..;
  
      pkt->size = ..;
  
      pkt->flags = bKeyFrame? AV_PKT_FLAG_KEY : 0;    
  
      pkt->dts = AV_NOPTS_VALUE;
  
      pkt->pts = PTS;
  
  
  
      // PTS is based on epoch microseconds so I ignored re-scaling.
  
      //av_packet_rescale_ts(pkt, { 1, AV_TIME_BASE }, muxTimebase);
  
  
  
      auto ret = av_interleaved_write_frame(m_pAVFormatCtx, pkt);

  I received a lot of error messages like this :
  "Application provided invalid, non monotonically increasing dts to muxer ...".

  Result : the mp4 file is playable via VLC but the FPS is just a half of the original FPS and the video duration is incorrect (VLC shows a weird number).

  So how do I set correct DTS and PTS before sending to the container ?

  Update :
  I have tried some changes, though not successfully yet, I found that the reason of the frame rate drop is due to the muxer discards frames having incorrect DTS.
  Additionally, if I set start of PTS and DTS value too big, some players like VLC has to delay some time before showing video.