[FFmpeg-devel] bug: snow encoder pred_block assertion. (sample data on upload.ffmpeg.org)

Chris Stones chris.stones
Wed Jul 1 22:27:12 CEST 2009

Hey guys... Im jumping in at the deep end, and attempting to solve the
problem with the following assertion.

ffmpeg: libavcodec/snow.c:2357: pred_block: Assertion `b_w>1 && b_h>1'

Before I spend too much time on this, can anyone confirm that it is indeed a
bug ?
With some failing sample media, this assertion fails on all versions of
ffmpeg i can get my hands on, right from todays svn (AMD64 Linux),
to very old unofficial win32 builds.

It doesnt seem to be a problem with the unusual resolution of the sample
media, as some sample data of the same res works fine.

I am converting a png flipbook animation to a snow video in a nut container
with the following command.

/usr/local/bin/ffmpeg -i snow_encoder_pred_block_assertion/gold%02d.png
-strict -2 -pix_fmt yuv420p -an -qscale 2.0 -f nut -vcodec snow gold.nut

I have uploaded some sample data to

As for solving this.. can anyone give me a kickstart in the correct
direction, like i say, im jumping right in at the deep end.

Thankyou very much for any help/direction.



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