[XviD-devel] corruption of VideoObjectLayer width and height values when setting frame rate at 8 fps

[Andrea Barbieri]

Hello,

AB:=Andrea Barbieri

AB> Hello,
AB> 
AB> I just found a peculiar bug in xvidcore-1.1.3 (I think it has been 
AB> present since version 1.0.0)
AB> 
AB> I have built the library and the example executables under CygWin.
AB> 
AB> when I use xvid_encraw like this: ./xvid_encraw -lumimasking 
AB> -framerate 7.5 -turbo -single -type 0 -i 
AB> /cygdrive/c/Users/ab/foo.yuv -o /cygdrive/c/Users/ab/foo1.xvid -w 
AB> 720 -h 480
AB> 
AB> or with any other frame rates (apart from 8.0) the VOL parameters 
AB> video_object_layer_width and video_object_layer_height are set 
AB> correctly to 720 and 480 respectively.
AB> 
AB> as soon as I switch to a framerate of 8.0 those two parameters get 
AB> corrupted to 1441 and 961 respectively (it looks like they get set 
AB> to twice plus one of the original values).
AB> 
AB> I am using MPEG4P2 parser to look inside the generated bitsream 
AB> http://sourceforge.net/projects/mpegparser/

looking into the actual source code for mpegparser it seems the 
computation of the number of bits to read from vop_time_inc_resolution 
could be wrong...

they use N rather than N-1 for the computation ... leading to a value of 
4 bits rather than the actual value of 3 bits (which is indeed 
used/written by xvid_encraw and xvidcore).

regards,
andrea
-- 
Andrea Barbieri
Moving Image Research http://www.movingimageresearch.com/
The Workshop, Hampton Lane, Bristol, BS6 6LE, UK
Tel: +44 117 9732200  FAX: +44 117 9732210
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