Mark Thompson: > On 08/02/2022 09:41, Andreas Rheinhardt wrote: >> L[i] can be in the range of 0-255, see table B.5 of ITU T.81. >> >> Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@outlook.com> >> --- >> libavcodec/cbs_jpeg.h | 2 +- >> libavcodec/cbs_jpeg_syntax_template.c | 4 ++-- >> 2 files changed, 3 insertions(+), 3 deletions(-) > > Do you have a valid file showing this? Not all values are allowed. >
Where is this said in the spec? The file jpg/12bpp.jpg from the FATE-suite triggers this. It has a Huffman table with 226 entries. (Sorry, should have mentioned the sample in the commit message.) > I guess I must have written it, but I have no idea where 224 came from. > As far as I know the worst case is in AC tables: 10 category values * 16 > run lengths + 2 special cases = 162 (which could indeed all be dumped in > the same code length if you want to be pathological). I have never heard of these restrictions. Would you care to elaborate which part of the spec they refer to? Anyway, IIRC there is no restriction against duplicates in the Huffman table, so one could use even more than 256 values (i.e. there might be spec-compliant pictures that are not supported by both our decoder and the current version of cbs_jpeg); it just makes no sense. Notice that the sample mentioned above has no duplicate values in any Huffman table. - Andreas _______________________________________________ ffmpeg-devel mailing list ffmpeg-devel@ffmpeg.org https://ffmpeg.org/mailman/listinfo/ffmpeg-devel To unsubscribe, visit link above, or email ffmpeg-devel-requ...@ffmpeg.org with subject "unsubscribe".
