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• ffmpeg first key frame pts negative

  16 juin 2020, par Keith

  First start the following rtsp sink :

  



  ffprobe -loglevel error -skip_frame nokey -select_streams v:0 -show_entries frame=pkt_pts_time -of csv=print_section=0 -rtsp_transport tcp -rtsp_flags listen -i rtsp://localhost:1554


  



  Then in another window, start the rtsp source :

  



  ffmpeg -hide_banner -f lavfi -i color -f rtsp rtsp://localhost:1554


  



  Result :

  



  -0.005000
0.475000


  



  


  How do I get the first key frame to start at 0 ? Isn't that what it should be ?

  


  



  I have tried things like

  



         -copyts -start_at_zero
       setpts=PTS-STARTPTS
       -avoid_negative_ts make_zero


  



  This sink :

  



  ffprobe -loglevel error -show_streams -rtsp_transport tcp -rtsp_flags listen -i rtsp://localhost:1554


  



  displays :
 start_pts=-540
  
 start_time=-0.006000

  


• Negative or 0 second duration

  3 mars 2023, par Nif

  I recently came across plenty of weird videos with negative durations

  


  firstly 0 seconds :
https://cdn.discordapp.com/attachments/397056507243528203/739081902278836234/short_video.webm

  


  And negative duration :
https://cdn.discordapp.com/attachments/397056507243528203/739081962211377152/CorruptFile.webm

  


  I tought it was a trick with webms but there also is a mp4 :
https://cdn.discordapp.com/attachments/397056507243528203/739081981643718687/video0-21.mp4

  


  I would love to know how I can make videos like these

  


• ffmpeg crop with negative offset

  12 août 2020, par Ajouve

  I have a nodejs application which is cropping videos using ffmpeg

  


  From time to time I have an error because I am trying to crop out of the video, see attached image where the black is the video and in red the crop zone. My final video has to be a square.

  


  

  


  If I am replacing the negative offset with 0 the final result will not be a square.

  


  I just need to add a black background on the non-existing part

  


  This is my actual code

  


  const cropVideo = (buffer, width, height, x, y) => {

    const inputFile = tmp.fileSync();
    const outputFile = tmp.fileSync();

    fs.writeFileSync(inputFile.name, buffer);

    return new Promise((resolve, reject) => {
        ffmpeg(inputFile.name)
            .videoFilters(`crop=${width}:${height}:${x}:${y}`)
            .format('mp4')
            .on('error', reject)
            .on('end', () => resolve(fs.readFileSync(outputFile.name)))
            .save(outputFile.name);
    })
}