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• FFMPEG Conact Demuxer Re-Encoding When Trying to Merge MP4s

  6 avril 2022, par Kyle Sinko

  I am trying to merge MP4 recordings straight out of OBS together into one MP4. From what I understand, I am using the concat demuxer to achieve this as it merges the files "extremely quickly" without re-encoding.

  


  I am using the command

  


  ffmpeg.exe -f concat -safe 0 -i "mylist.txt" -c copy video.mp4


  


  as explained in this post

  


  


  

  2. concat demuxer Use this method when you want to avoid a re-encode and your format does not support file-level concatenation (most files
used by general users do not support file-level concatenation).

  


  


  


  The command runs successfully, but the process takes a very long time. I assume the videos are being re-encoded as this is what shows :

  


  


  Output #0, mp4, to 'video.mp4' : Metadata :
encoder : Lavf58.51.100
Stream #0:0(und) : Video : h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x2160 [SAR 1:1 DAR 8:9], q=2-31, 1

  


  


  I'm unsure as to why the process is taking so long and want to know how I can merge the MP4 files into a single MP4 output file almost instantly.

  


• fftools/ffplay : do not write out of rdft visualization texture

  3 mars 2021, par Marton Balint

  fftools/ffplay : do not write out of rdft visualization texture
  If the window is resized it was possible that xpos pointed outside the
  
  visualization texture. By rearranging the overflow check we make sure this (and
  
  a crash) does not happen.
  We also don't have to use xleft for start position, as that is 0 anyways, and
  
  if we ever want to take into account xleft then the texture should be
  
  positioned accordingly when rendering.
  Signed-off-by : Marton Balint <cus@passwd.hu>
  

  • [DH] fftools/ffplay.c

• screen recording and video encoding with ffmpeg

  2 septembre 2016, par Alexander M.

  1.we need to record screenshots into video with 2-3 fps. Quality - the minimum possible to make text on the screen readable, 256 colors. It is important to reduce the output video file size as much as possible.

  2.we’ve made a lot of tests, and currently the most suitable way is to make screenshots every 300-500msec, save them in PNG, then run ffmpeg to encode to H.267 with these params :

  ffmpeg -f image2 -i "C:\png5min\image%04d.png" -y -an -vcodec libx264 -preset veryfast -crf 30 "C:\output.mp4"

  3.is it the best way to get minimum output size with 2-3fps screencast ?

  4.the output file plays very quickly, codec by default concerns that images represent 25fps. But they are 2fps actually.
  Ok, but if we try to decrease the output frame rate, output file size increases for about twice !! (from 3mb to 6mb for a 3m:26s video). And if we set the output frame rate as 2 - video does not play frames at all or plays just 2 frames for 3mins... :

  -r 2 -f image2 -i "C:\png5min\image%04d.png" -y -an -vcodec libx264 -preset veryfast -crf 30 -r 2 "C:\image5min_2fps_crf30_test__R2-2.mp4"

  so, how can we just add some latency after each frame without increasing the output file size ???