[FFmpeg-devel] [PATCH] avutil: make AVFrameSideData buffers ref-counted.

[Ronald S. Bultje]

Hi,

On Mon, Mar 23, 2015 at 12:15 PM, wm4 <nfxjfg at googlemail.com> wrote:

> On Mon, 23 Mar 2015 11:02:30 -0400
> "Ronald S. Bultje" <rsbultje at gmail.com> wrote:
>
> > Hi,
> >
> > On Mon, Mar 23, 2015 at 3:41 AM, Nicolas George <george at nsup.org> wrote:
> >
> > > Le duodi 2 germinal, an CCXXIII, Ronald S. Bultje a écrit :
> > > > ---
> > > >  libavutil/frame.c | 171
> > > +++++++++++++++++++++++++++++++-----------------------
> > > >  libavutil/frame.h |   1 +
> > > >  2 files changed, 98 insertions(+), 74 deletions(-)
> > >
> > > What consequences does it have for API users ? If there are not, do you
> > > know
> > > why it was not done from the start?
> >
> >
> > I asked that on IRC yesterday. The best answer I got was "probably
> because
> > this data is usually small". Which is true for most fields, but not all
> > (e.g. mvs).
>
> Well, you're really coming up with a special-case here. Side-data as
> designed really just included additional parameters and such, and no
> bulk data. On the other hand, nothing really speaks against extending
> AVFrame for refcounted side-data.
>
> Maybe very small side-data should not be refcounted, because the
> refcounting adds at least 2 more malloc allocations per side-data.


I can add non-refcounting for whatever side threshold you come up with. I
don't mind supporting non-refcounted side data (it's trivial).

> Consequences for API users is that people that wrote their own personal
> > av_frame_new_side_data() function are going to be screwed. There's some
> > code in av_ref_frame() to deal with that for image planes (if !buf alloc
> > new mem and memcpy), which we could theoretically do here as well. I'm
> not
> > sure we care about people messing with our public structures outside the
> > provided api, though...
>
> Uh, no, this is not how we should do things. You clearly define what's
> included in ABI and API, and what not. But it seems this question is
> not easily answered in this case. Did you ask Anton?


It's undocumented so I don't know what we want to include as part of
abi/api. We can do this any way you guys want. I just want some side-data
to be ref-counted.

Ronald