Re: [FFmpeg-devel] [PATCH v2] lavu/opt: Clarify that AVOptions is not indended for general use

From: Andrew Sayers <ffmpeg-devel@pileofstuff.org>
To: FFmpeg development discussions and patches <ffmpeg-devel@ffmpeg.org>
Subject: Re: [FFmpeg-devel] [PATCH v2] lavu/opt: Clarify that AVOptions is not indended for general use
Date: Tue, 23 Apr 2024 19:52:49 +0100
Message-ID: <ZigDgbvCtIeJMOcg@andrews-2024-laptop.sayers> (raw)
In-Reply-To: <CABLWnS8KkkctYRj-B1H=fAnWzfpt4H9no+0uwpR_ucsY7jNHCw@mail.gmail.com>

On Tue, Apr 23, 2024 at 10:28:38AM -0700, Vittorio Giovara wrote:
> On Tue, Apr 23, 2024 at 4:55 AM Andrew Sayers <ffmpeg-devel@pileofstuff.org>
> wrote:
> 
> > The hypothetical me wants not to throw away a week's work
> > because he did everything through AVOptions then came across some edge case
> > that doesn't fit into the AVOptions model.
> 
> 
> Out of curiosity, what are those edge cases?

It's really more a question of how to recover from the thing you didn't think
of, which makes it hard to think of good examples ;)

But since you ask, it might be worth looking at SANE option descriptors[0].
They perform a very similar function to AVOptions (providing a flexible
configuration API for a C codebase), and have a 90% overlap in features.  But
for example, SANE doesn't have an equivalent of AVRational, while AVOptions
doesn't have an equivalent of option groups.  More importantly, some things are
technically compatible but perform unobviously different jobs, like how SANE's
"description" text seems to do the same as FFmpeg's "help" text, but if memory
serves descriptions are usually several paragraphs while help is usually a
sentence or two.  It would waste a lot of time if I coded up a whole program
only to discover the SANE config screen had nicely-grouped options with
novel-length tooltips, while the FFmpeg config screen had a flat list of
well-described options that would have looked good if I'd picked an interface
with a search bar.

In a situation like that, it would be very helpful to know that FFmpeg's
position is "have a go and send us a patch if it works" rather than e.g. "we
never got round to making that private" or "we're in the middle of spinning
that off as a standalone library".  I'll have a think overnight and submit an
updated patch tomorrow based on everyone's feedback (thanks!).

[0] http://www.sane-project.org/html/doc011.html#s4.2.9
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