[FFmpeg-devel] About avpicture_alloc (deprecate?)

[Reimar Döffinger]

On Wed, May 05, 2010 at 10:06:55PM -0700, Baptiste Coudurier wrote:
> On 5/3/10 12:38 AM, Cyril Russo wrote:
> >
> >Le 02/05/2010 19:45, Reimar D?ffinger a ?crit :
> >>On Sun, May 02, 2010 at 07:31:44PM +0200, Cyril Russo wrote:
> >>>As soon as you use swscale, you need it.
> >>>avcodec_alloc_frame allocate the frame structure but not the "data"
> >>>buffer, while avpicture_alloc does.
> >>>
> >>>So unless you want people starting to allocate data[0] et al, by
> >>>themselves (and doing bad thing with alignment since it's very hard
> >>>to find out the required stride for decoder, see issue1909)
> >>The get_buffer functions are for allocating the data, and their
> >>documentation also explains how to get proper values _if_ you want
> >>to implement them yourselves (which is a good idea if performance is
> >>important).
> >The fact is when you're using swscale, you need an allocated picture
> >that is likely not in the same format of the decoded picture.
> >You can't call codecContext.get_buffer as it'll allocate (or reuse, the
> >doc doesn't say) a picture in the format expected by the codec.
> >
> >Let's take an example then, you want to convert YUV420P to RGB24.
> >How do you allocate the RGB24 picture without avpicture_alloc (and make
> >sure about the alignement requirement of swscale's algorithms) ?
> 
> Yes, that is right, avpicture_alloc is needed and must be part of
> the public API.

That surely is a exaggeration, quite a few users will implement
their own allocation functions anyway, but I see it is more
convenient.