[FFmpeg-devel] [PATCH] snow: remove strange av_assert2

Andreas Cadhalpun andreas.cadhalpun at googlemail.com
Thu Jul 9 20:24:52 CEST 2015

On 08.07.2015 18:07, Michael Niedermayer wrote:
> On Wed, Jul 08, 2015 at 07:24:13AM -0400, Ronald S. Bultje wrote:
>> - last of all, I want to remind you guys that we haven't done a very
>> thorough code analysis to see if this can actually be triggered. As an
>> example, look at commit 458446acfa1441d283dacf9e6e545beb083b8bb0. Before
>> that, vp8 files smaller than 16x16 or vp9 files smaller than 64x64 could
>> cause aborts. The vp9 ones I noticed due to some fate files being so small.
>> I doubt you'll ever find such vp8 files, but they're valid.
>> Let's not add silly checks to replace other silly ones.

Do you have any vp9 files triggering this assert?

> if people prefer i ca revert b8c438e7623644edcfdb508c946a723a3b79b893
> or add a check for stride == 0
> what do people prefer ?

The assert can be triggered by the h264 decoder:
mc_dir_part in libavcodec/h264_mb.c calls the 16 bit variant of
emulated_edge_mc and thus the assert is triggered due to the
sizeof(pixel) factor, even though block_w is smaller than buf_linesize.

If that's valid behavior of the h264 decoder, then the assert should
be removed, but if on the other hand this is a bug in the h264
decoder, then that should be fixed and the assert remain.

Best regards,

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