On Sun, Aug 30, 2015 at 8:22 PM, wm4 <nfx...@googlemail.com> wrote: > On Sun, 30 Aug 2015 18:09:05 +0000 (UTC) > Carl Eugen Hoyos <ceho...@ag.or.at> wrote: > >> wm4 <nfxjfg <at> googlemail.com> writes: >> >> > Change the default to blend with black, which >> > gives generally expected results. >> >> Given that this introduces a speed regression, is >> rarely needed and it is immediately visible that >> the function is needed, I don't think this is a >> sensible change. > > Performance is no argument in this case. Alpha video is rare in the > first place, so it won't affect most ffmpeg uses. Also, you can assume > the alpha channel exists for a reason. > > As for speed, the user can always disable alpha blending. I'd rather > prefer sane, correct default behavior, over fast and broken. > >> Note that contrary to visual issue, the performance >> regression is not immediately visible. > > It's the other way around. Did you even look at the test video in the > issue tracker? Judging whether the result is correct requires manual > checking of the whole video. On the other hand, libswscale is an > obvious thing to check when the conversion seems to be going too > slowly. libswscale is known not to be the fastest, especially with > "obscure" pixel formats. > >> And "black" may be sensible for prores, in all >> other cases, it is either suboptimal or bad. > > Such as? Name all the counter examples you know. I'm curious. > > But side from that, blending with _any_ color is still more reasonable > than discarding the alpha.
I agree, simply discarding information is not a good default. Defaults should be for reference quality, and degrading-but-faster modes should be options. - Hendrik _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
