[FFmpeg-devel] [PATCH, v2] avcodec/amfenc: increase precision of Sleep() on Windows

[Kieran Kunhya]

On Mon, Aug 19, 2024 at 7:31 PM Timo Rothenpieler <timo at rothenpieler.org> wrote:
>
> On 19.08.2024 16:23, Araz Iusubov wrote:
> > From: Evgeny Pavlov <lucenticus at gmail.com>
> >
> > This commit increase precision of Sleep() function on Windows.
> > This fix reduces the sleep time on Windows to improve AMF encoding
> > performance on low resolution input videos.
> >
> > Fix for issue #10622
> >
> > We evaluated CreateWaitableTimerExW with
> > CREATE_WAITABLE_TIMER_HIGH_RESOLUTION flag. In fact, this function has
> > the same precision level as the Sleep() function.
> >
> > Usually changing the time resolution will only affect the current
> > process and will not impact other processes, thus it will not cause a
> > global effect on the current system. Here is an info from
> > documentation on timeBeginPeriod
> > https://learn.microsoft.com/en-us/windows/win32/api/timeapi/nf-timeapi-timebeginperiod
> >
> > "Prior to Windows 10, version 2004, this function affects a global
> > Windows setting. For all processes Windows uses the lowest value (that
> > is, highest resolution) requested by any process. Starting with
> > Windows 10, version 2004, this function no longer affects global timer
> > resolution. For processes which call this function, Windows uses the
> > lowest value (that is, highest resolution) requested by any process.
> > For processes which have not called this function, Windows does not
> > guarantee a higher resolution than the default system resolution."
>
> Even modifying the current process is not acceptable, since lavc is
> frequently embedded in other applications, which might not expect
> this/be aversely impacted by it.
>
> Why does the AMF wrapper need to sleep at all?

Agreed, we can't have things like this in FFmpeg. This might be
acceptable in a binary blob but not in an open source project.

Kieran