Hi ffmpeg folks, This is based on a report on WebP issue tracker: https://code.google.com/p/webp/issues/detail?id=266
Looks like ffmpeg's native WebP muxer always sets ALPHA_FLAG to be true in VP8X chunk: https://github.com/FFmpeg/FFmpeg/blob/master/libavformat/webpenc.c#L110 (Even for a completely opaque image: e.g. an animated image where none of the frames have transparency info). But according to the WebP container spec: https://developers.google.com/speed/webp/docs/riff_container?hl=en#extended_file_format <Quote> Alpha (L): 1 bit Set if any of the frames of the image contain transparency information ("alpha"). <Unquote> This needs to be corrected. I took a dig at this, but it seemed non-trivial: ffmpeg needs to find out if there is "at least one frame containing transparency" -- this could be through (i) an ALPH chunk or (ii) inside a VP8L chunk. While, detecting case (i) is easy due to the presence of ALPH_FLAG in VP8X chunk, the same is not true for (ii) as in that case VP8X chunk may not be present. Can someone think of a good solution? Thanks, Urvang _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
