[FFmpeg-devel] LIBMPEG2_BITSTREAM_READER vs. golomb.h

Måns Rullgård mans
Mon Jul 14 03:20:32 CEST 2008

Loren Merritt <lorenm at u.washington.edu> writes:

> On Mon, 14 Jul 2008, M?ns Rullg?rd wrote:
>> To avoid future mishaps, I was thinking of adding a preprocessor check
>> to golomb.h (I'm too lazy to try to make it work).  What exactly is
>> the requirement here?  The code seems to assume 32 bits are available,
>> even though ALT_BITSTREAM_READER only promises 25 bits.  Clearly,
>> those 25 bits are sufficient for actual data.  Briefly looking at the
>> H.264 spec, I can't find any mention of a maximum length for
>> exp-golomb codes.  Did I miss something, or is there really no limit?
> The standard doesn't specify a bit limit as such, but the largest
> syntax element that's golomb coded is mvd=+/-4095.75 which is 29 bits.

Does that mean our reader would fail, if such a long golomb code were

M?ns Rullg?rd
mans at mansr.com

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