[Ffmpeg-devel] MPEG4: error in handling interlaced direct-mode macroblocks

[Michael Niedermayer]

Hi

On Sun, Mar 19, 2006 at 09:15:45PM +0000, Rahul Kumar wrote:
> Hi everybody,
> 
>     Finally I seem to be having some clue as to why this happens. Here
> is the story in brief:
> 
> FFMPEG directly applies the equations of section 7.7.2.2 (of the
> standard), for a interlaced direct-mode macro-block. However since
> FFMPEG stores motion vectors as field motion vectors, (for field
> macroblocks  mv=mv/2), this prodoces erroneous result. I think the
> cleanest way to solve this problem would be to always store the motion
> vectors as frame motion-vectos, irrespective of the block-type, and
> perform adjustment for field-based macroblocks in mpeg_motion() or
> qpel_motion().
> 
> Also note that FFMPEG doesn't set the correct field_select parameters
> for direct-mode macroblocks.
> 
> Hope this would help others (if any) who are trying to debug this stream..

i think ive fixed the field_select stuff, is everything correct now or is
it still buggy?

[...]
-- 
Michael