[FFmpeg-user] Same binary and same command 1 byte difference first frame

Andrew Sinclair ajsinclair at gmail.com
Tue Sep 4 06:29:57 EEST 2018

On Tue, 4 Sep 2018 at 09:15 Carl Eugen Hoyos <ceffmpeg at gmail.com> wrote:

> 2018-08-31 2:57 GMT+02:00, Andrew Sinclair <ajsinclair at gmail.com>:
> > Bit of a long shot here in case anyone may know, I am running the same
> > binary of ffmpeg on the same docker image on 2 different hosts and as a
> > result I get a different sized first I frame (out by 1 byte) between the
> 2
> > hosts, anyone have any idea how that could happen or know any settings I
> > could try to make the frames identical? I tried crf and disabling asm on
> > x264
> asm is always bit-exact as far as I know.
> Apart from the fact that this is not x264-users, you could test with one
> thread.

yes setting the threads does the trick, the issue is that the header
written by x264 in the SEI is of variable length and if the number of
threads changes based on the underlying hardware from say 6 to 11 (as it
was in my case) when running in the different containers that caused the

> Carl Eugen
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