On Wednesday 13 April 2016 10:27:03 am you wrote: > On Tue, 12 Apr 2016 19:53:13 +0000 (UTC) > > Carl Eugen Hoyos <cehoyos at ag.or.at> wrote: > > wm4 <nfxjfg <at> googlemail.com> writes: > > > > - flags |= 2 + 16; > > > > + flags |= 2; > > > > + if (st->codecpar->format != AV_PIX_FMT_YUV420P) > > > > + flags |= 16; // stream may contain transparency > > > > information > > > > > > The pixel format shouldn't be required to be set in this muxer. > > > > I am sorry, I don't understand the word "should" in this > > sentence: Do you mean the webp specification is bad or > > that the muxer should use a different information to > > find out if the frames may contain transparency? > > Or that the ticket is invalid or that I misunderstand it? > > No, I'm just saying that using the pixel format here (or how it's used) > is not overly robust. > > Maybe there is not better way to signal alpha content to the muxer, but > even then it sounds wrong to assume alpha if the format is not set.
Generally, I don't think assuming alpha for yuva420p and bgra is wrong. > Maybe it should just check whether the pixel format is alpha, instead > of whether it's not yuv420p. (Just a suggestion.) Isn't that exactly equivalent to what my patch is doing? Or do I just misunderstand? I just thought that "if (pix_fmt != AV_PIX_FMT_YUV420P)" is shorter than "if (pix_fmt == AV_PIX_FMT_RGB32 || pix_fmt == AV_PIX_FMT_YUVA420P)". Do you disagree? > But ideally maybe it could be parsed from the image data? (I'm not sure > if that's feasible.) I don't think this makes sense, especially since the header is written for the first output frame afaict. I was able to test my original patch and it "fixes" reading the output file of the following command with current webpmux: $ ffmpeg -f lavfi -i color=d=1 out.webp The general "bug" cannot be fixed afaict, but fixing many standard use-cases makes sense imo. Please comment, Carl Eugen _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel