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
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