Recherche avancée

Sur d’autres sites (10428)

• FFMPEG - Speed up video for time lapse - quicker/faster ?

  15 juillet 2023, par Chad Baldwin

  Okay, I know this question has been asked a bajillion times. However, I have one small addition to the question that I haven't seem to have been able to find in my googling.

  



  I'm certainly not a pro at FFMPEG...I've been using the standard speed up/slow down template for FFMPEG, the one I'm using is :

  



  ffmpeg -i input.mp4 -filter:v "setpts=PTS/60" -an output.mp4


  



  I'm currently working with an hour long 4K/60FPS video...I want to shrink it down to about 30 seconds or so, so I'm using PTS/100, and I don't need audio...the problem is, this is taking FOREVER...which I completely expected it to.

  



  But as I'm sitting here waiting for it to finish...I can't help but wonder...is there a faster/more efficient way to accomplish this ? I know there's a lot of weird things about FFMPEG in regards to the order of the commands you use to speed up seek time, and presets and etc.

  


• avcodec_decode_video2 : what do the extra bytes prevent ?

  17 septembre 2013, par TopGunCoder

  In the documentation for avcodec_decode_video2 it gives the following warning :

  Warning :

  The input buffer must be FF_INPUT_BUFFER_PADDING_SIZE larger than the
  actual read bytes because some optimized bitstream
  readers read 32 or 64 bits at once and could read over the end. The
  end of the input buffer buf should be set to 0 to ensure that no
  overreading happens for damaged MPEG streams.

  If this were not implemented would this cause segmentation faults when overreading occurs ? Or would it potentially cause weird corruption ? I'm just curious as I have corruption and I'm not sure if this could potentially be causing my problem.

• flatten two audio tracks with ffmpeg

  9 février 2019, par theonlygusti

  I record video in OBS with two audio tracks, and I use this command to flatten it :

  ffmpeg -i "$file" -filter_complex \
  
    '[0:a:1]volume=1.0[l];[0:a:0][l]amerge=inputs=2[a]' -map '0:v:0' -map '[a]' \
  
    -c:v copy -c:a libmp3lame -q:a 3 -ac 2 "${file:r}"_flattened.mp4

  But I think this outputs to a potentially weird format, because QuickTime Player.app doesn’t play any audio with it, and when I import it into Final Cut Pro it doesn’t recognise it as having audio.

  However, IINA can play the file with audio correctly, and when I upload it to YouTube it has the correct audio.

  How do I output to the audio tracks correctly so that when imported into FCP the file will actually have audio ?