ffmpeg | branch: master | Ronald S. Bultje <rsbul...@gmail.com> | Fri Oct 14 13:01:27 2016 -0400| [be885da3427c5d9a6fa68229d16318afffe67193] | committer: Ronald S. Bultje
vp9: change order of operations in adapt_prob(). This is intended to workaround bug "665 Integer Divide Instruction May Cause Unpredictable Behavior" on some early AMD CPUs, which causes a div-by-zero in this codepath, such as reported in Mozilla bug #1293996. Note that this isn't guaranteed to fix the bug, since a compiler is free to reorder instructions that don't depend on each other. However, it appears to fix the bug in Firefox, and a similar patch was applied to libvpx also (see Chrome bug #599899). > http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=be885da3427c5d9a6fa68229d16318afffe67193 --- libavcodec/vp9.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-) diff --git a/libavcodec/vp9.c b/libavcodec/vp9.c index 779f2d5..1aab6ba 100644 --- a/libavcodec/vp9.c +++ b/libavcodec/vp9.c @@ -3705,11 +3705,10 @@ static av_always_inline void adapt_prob(uint8_t *p, unsigned ct0, unsigned ct1, if (!ct) return; + update_factor = FASTDIV(update_factor * FFMIN(ct, max_count), max_count); p1 = *p; - p2 = ((ct0 << 8) + (ct >> 1)) / ct; + p2 = ((((int64_t) ct0) << 8) + (ct >> 1)) / ct; p2 = av_clip(p2, 1, 255); - ct = FFMIN(ct, max_count); - update_factor = FASTDIV(update_factor * ct, max_count); // (p1 * (256 - update_factor) + p2 * update_factor + 128) >> 8 *p = p1 + (((p2 - p1) * update_factor + 128) >> 8); _______________________________________________ ffmpeg-cvslog mailing list ffmpeg-cvslog@ffmpeg.org http://ffmpeg.org/mailman/listinfo/ffmpeg-cvslog
