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I have been trying to write a script to merge multiple .mp4 videos using ffmpeg. As part of this process, while trying to alter the size found that it alters the timebase. However, for ffmpeg - concat demux all streams should be same or else after merge only the first part of the video plays well and stops abruptly.

I have tried both terminal way and also using fluent-ffmpeg. But unfortunately both gives same result.

  1. Original video Ex, org_video_1280x720.mp4

Stream #0:1(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1280x720, 812 kb/s, 25 fps, 25 tbr, 30k tbn, 60k tbc (default)

  1. after scaling down to 640x360 via terminal ffmpeg -i org_video_1280x720.mp4 -strict -2 -vf "scale=640:360" new_video_640x360.mp4

Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x360, 256 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)

  1. The fluent-ffmpeg way of sizing
ffmpeg(`/path/to/org_video_1280x720.mp4`).size(`640x360`). autopad().output(`/path/to/new_video_640x360.mp4`)
          .on('error', function(err, stdout, stderr) {
              console.log('Error: ' + err.message);
              console.log('STD Err: ' + stderr);
         })
         .on('end', function() {
              console.log('Split & Resizing Completed!');
         }).run();

Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x360, 253 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)

Notice the tbn & tbc changes after resizing; Actually I have to merge this with other video only by changing the resolution (as they were with these 25 fps, 25 tbr, 30k tbn, 60k tbc stream values); However as it alters the time_base, I was unable to do it. Hope, I am missing something in the process, as I am bit new to audio/video process. Looking for some tips/guidance to get this done!

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Add -video_track_timescale X to manually set a timescale of X.

ffmpeg -i org_video_1280x720.mp4 -strict -2 -vf "scale=640:360" -video_track_timescale 90k new_video_640x360.mp4

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  • Thanks @Gyan. Now with this option the tbn was fixed and the resulted stream was - 25 fps, 25 tbr, 30k tbn, 50 tbc; However, here the tbc value was new and it didn't change back to original - 25 fps, 25 tbr, 30k tbn, 60k tbc. – Muthu Thavamani Jan 21 at 16:46
  • so when I merge this video with others videos those has stream - Stream #0:1(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 640x360, 812 kb/s, 25 fps, 25 tbr, 30k tbn, 60k tbc (default) the resulted video has the same error while playing. And while concat process in terminal i got warning says Non-monotonous DTS in output stream 0:1; previous: 4016128, current: 3765360; changing to 4016129. This may result in incorrect timestamps in the output file. – Muthu Thavamani Jan 21 at 16:49
  • i hope this video error and warning was due to the tbc mismatch. – Muthu Thavamani Jan 21 at 16:51

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