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• FFmpeg does not always fully concat video ?

  25 juin 2014, par user3550401

  I’m trying to concat two video clips, sometimes i end up with only three fourths of the video, sometimes I only get one half, and sometimes i manage to get the whole thing. Anyone ever deal with this ? Here is my ffmpeg command :

  ffmpeg -i "concat:videos/clip1.ts|videos/clip2.ts"  -ar 44100  -b:a 128k -b:v 800k -vcodeclibx264 -bsf:v h264_mp4toannexb -f mpegts -t 120 videos/output.ts

  I just dont understand why sometimes it works perfectly and other times i only get part of the video.

• merge/combine two FFMPEG commands together into one command

  26 février 2021, par Mayank Thapliyal

  I have been processing videos for a while and I have been using ffmpeg to make my life easy. But there are two commands which I want to combine into single command :-

  


  Step 1 :- Divide a video vertically into two parts and then stack them horizontally

  


  ffmpeg -i usa.mp4 -filter_complex "[0]crop=iw:ih/2:0:0[top];[0]crop=iw:ih/2:0:oh[bottom];[top][bottom]hstack" -preset fast -c:a copy usa$.mp4

  


  Step 2 :- Combine 3 videos into single video (the video from Step 1 will be in between the start.mp4 and end.mp4)

  


  ffmpeg -i start.mp4 -i usa$.mp4 -i end.mp4 -vsync 2 -filter_complex "[0:v] [0:a] [1:v] [1:a] [2:v] [2:a] concat=n=3:v=1:a=1 [v] [a]" -map "[v]" -map "[a]" usa_.mp4

  


  Can anyone please combine the videos into single command.I will be then able to save a lot of computing time(I guess that)

  


  Thanks in advance

  


• FFmpeg Decklink playout audio PCM

  28 décembre 2019, par Rick Jansen

  I’m working on a ffmpeg playout application for Decklink but I’m facing some audio issues. I’ve seen other questions about this topic but none of them are currently helping.

  I’ve tried Reubens code (https://stackoverflow.com/a/15372417/12610231) with the swr_convert for playing out ffmpeg/libav frames to a Decklink board (this needs to be 16 bits PCM interleaved) but the audio sounds wrong. It sounds like it’s missing samples/ only getting half of the required samples).

  When I record the samples in a raw audio file and play it out with Audacity the timeline is half the length of the actual recording and playing the samples on double speed.

  I also tried the ’manual’ conversion (https://stackoverflow.com/a/15372417/12610231) but unfortunately, not the result I was hoping for.

  Here are some snippets of my code

  swr_ctx = swr_alloc();
  
  av_opt_set_int(swr_ctx, "in_channel_count", pAudioCodecCtx->channels, 0);
  
  av_opt_set_int(swr_ctx, "in_sample_rate", pAudioCodecCtx->sample_rate, 0);
  
  av_opt_set_int(swr_ctx, "in_channel_layout", pAudioCodecCtx->channel_layout, 0);
  
  av_opt_set_sample_fmt(swr_ctx, "in_sample_fmt", pAudioCodecCtx->sample_fmt, 0);
  
  av_opt_set_int(swr_ctx, "out_channel_count", 2, 0);
  
  av_opt_set_int(swr_ctx, "out_sample_rate", 48000, 0);
  
  av_opt_set_int(swr_ctx, "out_channel_layout", AV_CH_LAYOUT_STEREO, 0);
  
  av_opt_set_sample_fmt(swr_ctx, "out_sample_fmt", AV_SAMPLE_FMT_S16, 0);
  
  
  
  if (swr_init(swr_ctx))
  
  {
  
      printf("Error SWR");
  
  }

  ///

  ret = avcodec_decode_audio4(pAudioCodecCtx, pFrame, &frameFinished, &packet);
  
  
  
  if (ret < 0) {
  
      printf("Error in decoding audio frame.\n");
  
  }
  
  
  
  swr_convert(swr_ctx, (uint8_t**)&m_audioBuffer, pFrame->nb_samples, (const uint8_t *)pFrame->extended_data, pFrame->nb_samples);

  It also looks like that the FFmpeg packet contains out of 1 video packet en 2 audio packets, not sure what to do with the second audio packet, I already tried to combine the first and second audio package without any good result on the audio side.

  Any help is appreciated.