On 18.09.2014, at 08:45, Pascal Massimino <pascal.massim...@gmail.com> wrote: > Hi, > > the webp lossless doc was unclear regarding palette index falling out of > range. > See issue #206 [1] for the bug report. > The solution retained was to treat out-of-range index as color 0x00000000, > so we could keep the speed-up in libwebp (we use fake extra entries in the > cmap to handle out-of-bound values without the extra branch). > > The doc was clarified (along with few other loose ends) in patch #71605 [2] > Attached is the fix for ffmpeg's webp decoder to treat out-of-bound index > as transparent-black instead of reporting an error.
The spec now says "should be set". I don't fully understand why we would ordinarily expect out-of-range value. I also don't understand why the issue talks about speed loss in the decoder, when it is the encoder that decides to use out-of-bounds values. Why does the spec not e.g. say "the encoder MUST NOT produce out-of-range values. A decoder SHOULD interpret them as black" (in which case our decoder should still warn about the file being invalid). Also, a branch per pixel is not necessary even if the spec required creating an error, you could just or the result of the range check together, which could/should come in at maybe 1 cycle/pixel. _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-devel
