[FFmpeg-devel] [PATCH 3/4] fftools/opt_common: stop accessing a private field

[Anton Khirnov]

Quoting Alexander Strasser via ffmpeg-devel (2024-10-15 21:16:28)
> On 2024-10-15 15:09 +0200, Anton Khirnov wrote:
> > Quoting James Almer (2024-10-15 14:54:08)
> > > On 10/15/2024 6:57 AM, Anton Khirnov wrote:
> > > > avfilter_process_command() may or may not return ENOSYS whether that
> > > > flag is set or not, so I don't see what exactly would it be useful for.
> > >
> > > I see, although I wouldn't expect ENOSYS for any other case than
> > > "unsupported". If a command fails, imo it would be EINVAL, or maybe ENOMEM.
> >
> > Correct, but
> > * some commands work on all filters; for now it's just "ping", but we
> >   can add more in the future;
> > * the "enable" command works on all filters flagged with
> >   AVFILTER_FLAG_SUPPORT_TIMELINE; again, we may add more such
> >   "semi-generic" commands in the future;
> > * filters that do implement the process_command() callback will still
> >   return ENOSYS when you send them a command they do not support.
> >
> > So checking for the existence of process_command() does not really tell
> > you anything specific, and the same would hold for the hypothetical flag
> > that would replace it.
> >
> > >
> > > > Same holds for printing the capability in fftools - just what is the
> > > > user expected to do with that information?
> > >
> > > Know they can use the send command interrupt for a given filter without
> > > having it unconditionally fail, i guess. But for that matter, is the
> > > list of supported commands available anywhere for the user? Is there an
> > > API to query them, or is it expected to be only in the documentation?
> > > If there's no API, then maybe printing this is pointless.
> >
> > There is no such API, which I agree would be useful - but if it did
> > exist we would again not need the flag.
> 
> For me that flag is more about if some filter brings commands of its own.

Most filters implementing the process_command() callback just use
the generic implementation - ff_filter_process_command(). So what
information does that flag actually give you?

-- 
Anton Khirnov