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• Cut a video in between key frames without re-encoding the full video using ffpeg ?

  1er septembre 2020, par bguiz

  I would like to cut a video at the beginning at any particular timestamp, and it need to be precise, so the nearest key frame is not good enough.

  


  Also, these videos are rather long - an hour or longer - so I would like to avoid re-encoding this altogether if possible, or otherwise only re-encode a minimal fraction of the total duration. Thus, would like to maximise the use of -vcodec copy.

  


  How can I accomplish this using ffmpeg ?

  


  NOTE : See scenario, and my own rough idea for a possible solution below.

  


  ---

  


  Scenario :

  


  

  • Original video

    

    • Length of 1:00:00

    


    • Has a key frame every 10s

    


    


  


  • Desired cut :

    

    • From 0:01:35 through till the end

    


    


  


  • Attempt #1 :

    

    • Using -ss 0:01:35 -i blah.mp4 -vcodec copy, what results is a file where :

    


    • audio starts at 0:01:30

    


    • video also starts at 0:01:30

    


    • this starts both the audio and the video too early

    


    


  


  • using -i blah.mp4 -ss 0:01:35 -vcodec copy, what results is a file where :

    

    • audio starts at 0:01:35,

    


    • but the video is blank/ black for the first 5 seconds,

      

      • until 0:01:40, when the video starts

      


      


    


    • this starts the audio on time,
but the video starts too late

    


    


  


  


  ---

  


  Rough idea

  


  

  • (1) cut 0:01:30 to 0:01:40

    

    • re-encode this to have new key frames,
including one at the target time of 0:01:35

    


    • then cut this to get the 5 seconds from 0:01:35 through 0:01:40

    


    


  


  • (2) cut 0:01:40 through till the end

    

    • without re-encoding, using -vcodec copy

    


    


  


  • (3) ffmpeg concat the first short clip (the 5 second one)
with the second long clip

  


  


  I know/ can work out the commands for (2) and (3), but am unsure about what commands are needed for (1).

  


• How to measure delay in video streaming (RTMP) from NGinX server to video player in web browser ?

  2 mars 2020, par Padfoot

  I am streaming a MP4 file from AWS NGinX server (using FFMPEG) to a video player (currently using flowplayer in web page).
  I am trying to identify how long the player will take to get the first packet of frames from the server. Is there any utility or method to measure.

  I have already checked few previous questions in stackoverflow, and found out about webrtc chrome://webrtc-internals/.

• ultimate video player not working with one video (Uncaught in promise)

  29 octobre 2018, par completeidiothereDoh

  So I have a small website that I have yet to launch using PHP / MySQL. One section there is a video player, and I am using the Ultimate video player script beecause it easily allowed me to change some codes to insert ads, etc. So far I’ve only added about 20 videos, mostly downloaded from archive.org. The uploads are processed using FFMPEG, specifically this command :
  exec(’ffmpeg -i ’.$uploadfile.’ -f mp4 ’.$new_flv) ;

  I also do some other things with ffmpeg such as create an animated .gif and a video thumbnail. So far everything has worked. Prior to using the current video script I was using video.js and this issue didn’t happen. Once I switched over to the new script I noticed this one video won’t play. It acts like it wants to play (spinner spins for a few seconds) but ultimately goes back to the pre-play video thumbnail rather than playing the video.

  I am experiencing this in Google Chrome, though the same thing using Edge. The Chrome console messages reads as follows : Uncaught (in promise) DOMException : The play() request was interrupted by a call to pause().

  The video worked prior to switching to this video player. The file also works attempting to open in Windows. The file works opening directly in Chrome. Plus all other videos work except for this one. I contacted the author and was told that it sounds like an encoding issue and that he isn’t very good at that sort of thing.

  I won’t post the paid script’s js source file here, but I guess I am wondering if anything I’ve listed points to maybe he is correct (although then why did it work in video.js and not uvp ?) and my rudimentary ffmpeg mp4 conversion command needs some work, or else perhaps some of the research I’ve done on this google chrome console message can fix the issue. I don’t believe I can make the corrections myself but I’m curious if anyone suspects this is really an encoding issue.

  I’ve only managed to add about 20 videos, so so far 1/20, or 5% videos aren’t working. I am worried that ignoring a video that isn’t working now, once there are thousands of videos, then maybe 100 won’t work, etc. Furthermore, although probably mostly SERPS (since I haven’t technically launched yet), the video in question has the most views haha. So if it is attracting more organic traffic than the other videos I would obviously like to have it working again.

  I may need to move back to video.js, but the reason I switched was I was having a difficult time (not being an excellent coder) attempting to implement an ads system. Oh well, thanks if anyone has any suggestions or ideas.