[FFmpeg-user] on frame changes in recode

Xen list at xenhideout.nl
Wed Apr 27 20:31:41 CEST 2016


I was just taking a video from YouTube and, in this case, cutting off 
the largest part of the beginning of it, leaving only the end.

I have first used PiTiVi and later AviDemux and later tried ffpeg cmd 


This was ultimately the command line that I used:

ffmpeg -i input.mp4 -ss 00:5:50.800 -vcodec libx264 output.mp4

I don't know if its output is important.

The beginning of the scene starting at 00:5:50.800 of this file has a 
transition that is a cross-fade from the previous scene. The transition 
starts with the last full clear picture of the last scene, and then in 
10 steps fades into the next one.

So this is a transition that takes 10 steps (frames) to complete at 

Now I recoded it using Linux and the same transition now takes 11 steps 
to complete at 30fps.

All problems stem from these programs using the same library, I'm sure.

in this sequence of 11 frames the 2nd frame is always duplicated in the 

So you have the initial frame of the last scene, then the fading starts, 
the 2nd frame is a light crossfade beginning and the 3rd frame is 
identical to the 2nd frame. After that it proceeds as usual and as the 
original video file.

I have no clue if this behaviour is dependent on the type of video but I 
have done nothing else yet. It is so easy to see in this case because of 
it being a crossfade.

I don't get how it happens but I just want to have a frame by frame 
copy. I need to render because otherwise I won't have a starting 

The frames themselves are NOT changed but the 2nd frame is duplicated.

Any idea what's going on here?


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Regards, Xen.

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