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• MP4 cut with ffmpeg doesn't play nicely in VLC but does in Browser

  21 février, par Alex

  I cut a video with ffmpeg :

  


  ffmpeg -ss 2 -to 10 -i src.mp4 -c copy out.mp4


  


  But the playback in VLC is choppy for the first few seconds. Strangely it does play in my browser fine.

  


  I saw this post :
https://superuser.com/questions/1167958/video-cut-with-missing-frames-in-ffmpeg?newreg=1502e1698e0344acb214aa8d7e6048bd where the suggestion is to use -avoid_negative_ts make_zero. That does fix the playback in VLC. I think that shifts the whole stream, and results in the video being longer than I want it to be.

  


  For my use case I need the video to be precisely the correct length and I can't incur the cost of a (full) re-encode. I think the addition of -avoid_negative_ts is effectively snapping the cut to the nearest keyframe.

  


  So I think the negative timestamps are upsetting VLC ? I can see they exist.

  


  $ ffprobe -v error -select_streams v:0  -of  default=noprint_wrappers=1 out.mp4 -show_entries packet=pts | head
pts=-30720
pts=-30464
pts=-30208
pts=-29952


  


  I also tried with a few other media players (Films & TV in Windows) and had similar issues. Is there a better way to handle this, in a way that will allow the output video to be played normally ?

  


  I saw the approach in this question : Cut a video in between key frames without re-encoding the full video using ffpmeg ?. But had issues with "Non-monotonous DTS" that also seemed to manifest in choppy playback.

  


• An Electron RTSP player : How to play the video stream ?

  3 octobre 2023, par Siavoshkc

  What seemed to be an easy job turned out otherwise. I wanted to write an Electron app to manage DVR streams as I wasn't satisfied with some apps I used. I choose Electron because I recently started JS and took the opportunity to practice it and also play a bit with Electron.

  


  After deciding about how to handle GUI using web components, it was time to see how to read RTSP streams. My initial approach was to use FFmpeg. But I didn't know how to do so in Nodejs or Electron so I started a research.

  


  Long story short I understood that if one wants to use a C/C++ library in JS the best practice is to create bindings using Node API (formerly NAPI) which will result in a FFmpeg native addon. Then I assumed there is already a decent such addon available as FFmpeg is the go-to for video stuff. But to my surprise this isn't the case. Although there are some packages which run ffmpeg executive binary the ones that provide the binding are rare and not recent (such as beamcoder).

  


  FFmpeg web assembly is another option which I may consider but seemed overkill as I am not opening the streams in pure browser.

  


  Another approach was to use chromium media abilities as it has FFmpeg bundled for some media functions but to my understanding it cannot open RTSP streams at least for now.

  


  Can you please add to my current understanding on the matter ?

  


• An Electron RTSP player : How to play video stream ?

  26 octobre 2022, par Siavoshkc

  What seemed to be an easy job turned out otherwise. I wanted to write an Electron app to manage DVR streams as I wasn't satisfied with some apps I used. I choose Electron because I recently started JS and took the opportunity to practice it and also play a bit with Electron.

  


  After deciding about how to handle GUI using web components, it was time to see how to read RTSP streams. My initial approach was to use FFmpeg. But I didn't know how to do so in Nodejs or Electron so I started a research.

  


  Long story short I understood that if one wants to use a C/C++ library in JS the best practice is to create bindings using Node API (formerly NAPI) which will result in a FFmpeg native addon. Then I assumed there is already a decent such addon available as FFmpeg is the go-to for video stuff. But to my surprise this isn't the case. Although there are some packages which run ffmpeg executive binary the ones that provide the binding are rare and not recent (such as beamcoder).

  


  FFmpeg web assembly is another option which I may consider but seemed overkill as I am not opening the streams in pure browser.

  


  Another approach was to use chromium media abilities as it has FFmpeg bundled for some media functions but to my understanding it cannot open RTSP streams at least for now.

  


  Can you please add to my current understanding on the matter ?