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• FFmpeg encoding slow for 4K HDR content

  1er mars 2023, par Geno Diaz

  When processing 4K input with the following configuration it is taking upwards of 2 minutes to process a 35s, 60fps, 4K HDR clip recorded from an iPhone. Is this the expected performance or is there an inefficiency within the configuration that is causing this ?

  


  In comparison, running this configuration on a 35s, 30fps, 4K non-HDR clip, only takes about 20 seconds.

  


  ffmpeg 
-i "input path" 
-y 
-filter:v scale=w=2160:h=3840 
-threads 4 
-r 59.94 
-c:v libx264 
-preset veryfast 
-vsync 1 
-tune film 
-maxrate 6000k 
-bufsize 5400k 
-g 60 
-x264opts no-scenecut 
-c:a aac 
-af aresample=async=1:min_hard_comp=0.100000:first_pts=0 
-ac 2 
-b:a 128k 
-ar 44100 
-vf zscale=transfer=linear:npl=100,
  format=gbrpf32le,
  zscale=primaries=bt709,
  tonemap=tonemap=hable:desat=0,
  zscale=transfer=bt709:matrix=bt709:range=tv,
  format=yuv420p 
-sws_flags full_chroma_int+full_chroma_inp 
-pix_fmt yuv420p 
"outputfile".mp4


  


• How to extract time-accurate video segments with ffmpeg ?

  25 mai 2016, par Jim Miller

  This is not a particularly new question area around here, but I’ve tried what’s been suggested there without much luck. So, my story :

  I’ve got a hunk of 15 seconds of straight-from-the-camera.mov video out of which I want to extract a specific chunk, which I can identify by start time and stop time, in seconds. I started by trying to do what I’ll call a "copy extraction" : to get seconds 9 to 12,

  ffmpeg -i test.mov -vcodec copy -acodec copy -ss 9 -to 12 test-copy.mov

  This was a not-bad start, but there are some black frames at the beginning and end of the clip, which I can’t have — it has to be a clean edit from the original. So, I tried recoding the original into a new, trimmed clip :

  ffmpeg -i test.mov -ss 00:00:09 -t 00:00:03 test-out.mov

  This is better, but not quite : There are no longer any black frames at the beginning of the clip, but they’re still there at the end.

  After some more browsing and reading, I then suspected that the problem is that ffmpeg is having trouble finding the proper points because of a lack of keyframes in the original video. So I recoded the original video to (presumably) add keyframes, in a couple of different ways. Since I want to be able to pick video at boundaries of a second ("from 9 seconds to 12 seconds"), I tried, copying various suggestions around the web,

  ffmpeg -i test.mov -force_key_frames "expr:gte(t, n_forced)" test-forced.mp4

  and

  ffmpeg -i test.mov -g 1 test-g-inserted.mp4

  (I built these as mp4’s based on some comments about an mp4 container being needed to support the keyframe search, but I’m honestly just hacking here.) I then tried the extraction as before, but on these new videos that presumably now have keyframes in them. No luck — both seem to be about the same ; the start is OK but there are still black frames at the end. (FWIW, both test-forced.mp4 and test-g-inserted.mp4 also have trailing black frames.)

  So : I’m still stuck, and would like to not be. Any insights out there as to what I’m doing wrong ? I feel like I’m close, but I really need to get rid of those trailing black frames....

• How to join 3 movieclips with ffmpeg with an added overlay to the second one ?

  16 avril 2014, par Alex Khvorov

  I want to add an overlay image to the clip and then add two short clips at the start and end of it