[FFmpeg-user] setpts filter produces much smaller files

[George Welch]

On 5/21/25 12:19 PM, German Geraskin wrote:
> Hi,
>
> Well, I can confirm the problem.
> The problem is specific to the libx265 encoder and ffmpeg version n7.x.
> The problem does not depend on the platform.
>
> I tested on Windows (x86_64).
>
> # FFmpeg n4.4 and n7.1
> The libx264 encoder gives the same results in both cases,
> regardless of the (setpts) filter presence in the command.
>
> # FFmpeg n4.4
> The libx265 encoder gives the same results in both cases,
> regardless of the (setpts) filter presence in the command.
>
> # FFmpeg n7.1
> The libx265 encoder produces output files with significantly different
> bitrates and quality depending on whether the (setpts) filter is used or not.
>
> Obviously it is the bug!
>
> German Geraskin

German, this is fantastically helpful!  Thank you.  I believe this 
solves the problem.

I was very surprised that you found the bug in windows.  That's because 
I had found it on macos but not on linux.  So when I saw your email I 
was very surprised since I had assumed it was just a bug on the Mac version.

So I looked deeper and found out I was being stupid.  The version I was 
running on linux was not 7.1.1 as I thought, but was installed giving 
homebrew the --HEAD option.  The actual version was N-119658-g4099d53759.

I uninstalled that and installed 7.1.1 and boom, the bug was there on 
linux too.

I then uninstalled 7.1.1 on my Mac and reinstalled it with --HEAD. The 
Mac version is now N-119658-g4099d53759, and the bug is gone!

So we see this on macos, linux, and windows with 7.1.1, but it is gone 
on both mac and linux with N-119658-g4099d53759.

Perhaps this was a real bug that has been fixed since 7.1.1 was 
released.  Do you know where to see release notes that might shed light 
on it?

Thanks everyone.

--George