[FFmpeg-user] Different conversion results on similar conversion runs.

[Carl Eugen Hoyos]

Anatol <anatol2002 <at> gmail.com> writes:

> 
> First the command line u asked for:
> ffmpeg -i input.mp4 -c:v h264 

I asked for a command line that does not use 
external libraries (like x264).
The reason is that I know the FFmpeg version 
you are using (and I can test the exact version) 
if necessary but I cannot know your x264 version 
(and it takes a magnitude more effort to use the 
same version here). Since you said the problem 
is reproducible without external libraries, I'd 
like to test that.

> I got a hint from the FFmpeg Support Forum.
> It is about setting encoding side 'threads' 
> value (rather than decoding side in my 
> original post).

Yes, this is what I wrote this morning.
(It would be a bug if setting the decoder 
thread count to a different value made a 
difference.)

> I understand why there are differences when the 
> command line is executed with different threads 
> settings.

Good.

> I don't understand why execution of exactly the 
> same command line generates different files on 
> consecutive runs.

Then you apparently do not understand above...
(Or I don't but I suspect FFmpeg cannot know 
how much work your whole system has to do at 
a given moment, it cannot be multi-threaded 
and deterministic at the same time.)

Carl Eugen