[FFmpeg-devel] [PATCH] avfilter/vf_stereo3d: implement auto detection by using frame side data

[Michael Niedermayer]

On Fri, Dec 01, 2017 at 10:01:42AM +0100, Nicolas George wrote:
> Paul B Mahol (2017-11-30):
> > +static int reset_links(AVFilterContext *filter)
> > +{
> > +    int i, ret;
> > +
> > +    if (!filter)
> > +        return 0;
> > +
> > +    for (i = 0; i < filter->nb_outputs; i++) {
> > +        AVFilterLink *link = filter->outputs[i];
> > +
> > +        link->init_state = AVLINK_UNINIT;
> > +        link->frame_rate.num = link->frame_rate.den = 0;
> > +        link->w = link->h = 0;
> > +
> > +        ret = reset_links(link->dst);
> > +        if (ret < 0)
> > +            return ret;
> > +    }
> > +
> > +    if (!i)
> > +        return avfilter_config_links(filter);
> > +
> > +    return 0;
> > +}
> 
> Sorry, but no. All filters are currently written with the assumption
> that config_props is called only once. Not all of them actually rely on
> this assumption, but some do, and expect the fields of the private
> context to be in their initial state. Violating that assumption would
> result in a lot of memory leaks and probably a few crashes, some of them
> security relevant.
> 
> Plus, the public API of buffersink does not document params changes and
> does not provide a good way of reacting to it, so enabling params
> changes like that would have problematic results on applications that
> expect frames with all the same size.
> 
> (By the way, I am quite worried to see that Michael weakened the
> protections for that last point in 5d859e59809.)
> 

> Filters reconfiguration has been wanted for a lot of time. If it was
> that simple, it would have been done already. If you want to implement
> it, please go ahead, but it will not be an easy task.

As the one who tried implementing changing frame parameters like
dimension long time ago, the only real problem i encountered was
bikeshedding, i dont rememer a technical problem. The bikeshedding in
fact resolved itself but by the time i had lost interrest ...

And in fact many filters should just be able to handle changing frame
parameters as they are or with minimal changes.

[...]


-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

During times of universal deceit, telling the truth becomes a
revolutionary act. -- George Orwell
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 181 bytes
Desc: Digital signature
URL: <http://ffmpeg.org/pipermail/ffmpeg-devel/attachments/20171201/ee91d0c3/attachment.sig>