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• Ffmpeg : How to account for the changing bounding box size due to rotation

  29 janvier 2020, par Ronak Makwana

  I have multiple input gif and image files to overlay on video. following is command i was trying but didn’t get actual result.

  -y -i Gromoverlayvideo.mp4 -ignore_loop 0 -i chtOekuyI69C4enhdN.gif -ignore_loop 0 -i ZahTVRkpwweJPf9EMO.gif -filter_complex [0:v]scale=iw:ih[outv0];[1:0]scale=411.3303:228.64946,rotate=41.0*PI/180:c=none:ow=rotw(41.0*PI/180):oh=roth(41.0*PI/180)[outv1];[2:0]scale=336.3402:185.56363,rotate=-32.0*PI/180:c=none:ow=rotw(-32.0*PI/180):oh=roth(-32.0*PI/180)[outv2];[outv0][outv1]overlay=9:329:shortest=1[outo0];[outo0][outv2]overlay=255:478:shortest=1 -r 25 -preset superfast 1580281804661.mp4

  this is what i want.

  

  this is result :

  

  kindly help me calculate x and y overlay points according input height and width and rotation angel.
  thanks

• FFMPEG "volumedetect" filter in C++

  20 mars 2020, par Hrethric

  I am hoping to use FFMPEG to calculate the volume of my audio files, but find the documentation a bit lacking on this particular issue. Basically I’m trying to do something similar to the following command :

  ffmpeg -i "myfile.mp3" -filter:a volumedetect -f null /dev/null

  But in C++. So creating the filter, and passing my audio frames to the filter seems relatively straightforward by doing something along the lines of :

  avfilter_register_all();
  
  _volumeFilter = avfilter_get_by_name("volumedetect");
  
  
  
  _filterGraph = avfilter_graph_alloc();
  
  
  
  _volumeFilterCtx = avfilter_graph_alloc_filter(_filterGraph, _volumeFilter, "volumedetect");

  The above code is all successful from a standpoint of initializing the filter. Then when I read a frame I basically do :

  if (frameFinished) 
  
  {
  
      /* push the audio data from decoded frame into the filtergraph */
  
      if (av_buffersrc_add_frame_flags(_volumeFilterCtx, _audioFrame, 0) < 0) 
  
      {
  
          av_log(NULL, AV_LOG_ERROR, "Error while feeding the audio filtergraph\n");
  
          break;
  
      }
  
      /* pull filtered audio from the filtergraph */
  
      while (1) 
  
      {
  
          ret = av_buffersink_get_frame(_volumeFilterCtx, _filteredFrame);
  
          if (ret == AVERROR(EAGAIN) || ret == AVERROR_EOF)
  
                  break;
  
      }
  
  }

  This is where I’m not sure what to do. With regular audio filters it affects the underlying data, and you can just use the resulting frame. With this though, I need to pull data out of the filter to tell me what the volume is. How do I do this ? Or am I going about this the wrong way ?

  Again I simply can’t find any documentation on this, so thanks in advance for the help !

• decoding an input video using FFmpeg command

  2 février 2023, par david

  How can I decode an input video using an FFmpeg command ?
  
My input videos have ts format.

  


  I am not very familiar with FFmpeg and the command that I found for decoding, decodes the input video to YUV output that can not be displayed.

  


  Question :
  
Which FFmpeg command can I use to decode the input video to the showable file ?

  


  This command below decodes the input video to YUV, but I need a command to decode the video to the same format as input to calculate PSNR between them.

  


  ffmpeg -i input.ts -f rawvideo -pix_fmt yuv420p output.yuv


  


  


  • If I choose ts instead of YUV, it produces a video file that is invalid for FFmpeg.
    What is the problem ?

    


  


  • How can I decode an input video to playable format ?

    


  


  


  Is this command wrong for decoding ?

  


  ffmpeg -i input.ts -f rawvideo -pix_fmt yuv420p output.ts