[FFmpeg-devel] [PATCH] avcodec: Require avoptions for the user to set max_pixels.

Michael Niedermayer michael at niedermayer.cc
Sun Dec 11 02:23:17 EET 2016

On Sat, Dec 10, 2016 at 08:31:57PM -0300, James Almer wrote:
> On 12/10/2016 7:01 PM, Michael Niedermayer wrote:
> > When we will backport this, it will be inevitably in a different location
> > in AVCodecContext in each release and master. 3.0, 3.1, 3.2 and master
> > use the same soname though and must have a binary compatible interface.
> > It thus can only saftely be accessed through AVOptions
> > 
> > It may be enough to require this only in the releases but that could be
> > rather confusing.
> Wouldn't it be better to initially add such new fields inside
> AVCodecContext->internal and accessible by AVOptions only so they
> may be trivial to backport, then once a major bump occurs they can
> be moved to the actual public struct with enabled direct access?
> Not sure how feasible is to have options_table.h options change
> values from that internal struct, but it would solve the above
> concerns.

AVCodecInternal does not start with a AVClass / AVOption table
(thats solvable though would need to be done to past releases)

AVCodecContext->internal is not a child class of AVCodecContext
(that is solvable too, if we want to take the risk to do that in
 point releases)

AVCodecContext->internal is allocated in avcodec_open2() so nothing
can be set in it by the user before
(i dont see a solution to this that we would want to backport)

If you suggest to make these changes now to for future use.
that will make backports across this change very annoying, as theres
a point before AVCodecInternal cannot be used.
And also theres more work for us to maintain seperate implementations
for the options, all code accessing them has to deal with them being
in different places, making all related backports harder.

To me that looks like a disadvantage from every side

I think the real solution is to start liking AVOptions, they make
our work easier.

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The bravest are surely those who have the clearest vision
of what is before them, glory and danger alike, and yet
notwithstanding go out to meet it. -- Thucydides
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