Quoting Mark Thompson (2016-03-10 16:56:21)
> >> + ++avfc->nb_surfaces;
> >> + if (avfc->nb_surfaces == 1) {
> >> + // Test whether vaDeriveImage() works for this type of surface.
> >> + VAImageFormat *expected_format;
> >> + VAImage test_image;
> >> + int err;
> >> +
> >> + ctx->derive_works = 0;
> >
> > I think this is unsafe, since this variable is also accessed in
> > mapping the frame, which can easily happen concurrently with this
> > function. So it would be better to make this test in frames_init.
> > Also, this function won't be called at all if the caller supplies his
> > own frame pool. The mapping function should work even then.
>
> So call get_buffer() at the end of frames_init() and try the mapping there?
> That might be slightly surprising to the user supplying their own pool, but
> otherwise seems entirely reasonable.
I think just creating a single dummy surface with a random format and
calling derive on it might be simpler.
--
Anton Khirnov
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