[FFmpeg-devel] [PATCH]Fix utvideo regression

Michael Niedermayer michaelni at gmx.at
Mon Jun 9 14:52:58 CEST 2014

On Mon, Jun 09, 2014 at 01:18:13PM +0200, Christophe Gisquet wrote:
> Hi,
> 2014-05-29 12:27 GMT+02:00 Derek Buitenhuis <derek.buitenhuis at gmail.com>:
> > Have you tried the sample with the official decoder? If that breaks, then its not our
> > decoder which needs to be fixed, but our encoder.
> Actually, probably both.
> Non-existing symbols may get a codelength of e.g. 30 or 31, in turn
> causing the initial issue with the vlc parsing code. There's even a
> bogus "get_vlc2(&gb, vlc.table, vlc.bits, 4)" in the code (max_depth
> above 3 is meaningless).
> The issue is that utvideo writes a codelength of 255 for those values
> and special-case them in various places. ffmpeg's version tries to
> account for this, but somewhat fails, in particular by writing
> whatever ff_huff_gen_len_table outputs for absent symbols. This
> probably causes less optimal decoding for utvideo official decoder.

all fixed
will push after organizing in commits and some testing

> ffmpeg codec should probably uses 0 as length internally, depending on
> what ff_init_vlc_sparse prefers.
> -- 
> Christophe
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Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

it is not once nor twice but times without number that the same ideas make
their appearance in the world. -- Aristotle
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