[FFmpeg-devel] [PATCH] lavu/opt: Mention that AVOptions is not reentrant

Paul B Mahol onemda at gmail.com
Wed Jun 5 16:50:55 EEST 2024


On Wed, Jun 5, 2024 at 3:44 PM Andrew Sayers <ffmpeg-devel at pileofstuff.org>
wrote:

> On Wed, Jun 05, 2024 at 03:34:50PM +0200, Paul B Mahol wrote:
> > On Wed, Jun 5, 2024 at 3:18 PM Andrew Sayers <
> ffmpeg-devel at pileofstuff.org>
> > wrote:
> >
> > > An external API developer might think they can use AVOptions to modify
> > > values
> > > during playback (e.g. putting a playback quality slider next to the
> volume
> > > slider).  Make it clear that behaviour is not recommended.
> > >
> >
> > There are options that can be changed at runtime,
> > And it works just fine.
>
> How would an external developer know which options can be safely changed
> (preferably including in future versions of FFmpeg) vs. ones where their
> tests
> got lucky and happened not to trigger a read during a non-atomic write?
>

See this flag:

#define AV_OPT_FLAG_RUNTIME_PARAM   (1 << 15)

What is the point/gain in changing options from multiple threads
concurrently?



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