[Mp4-tech] CABAC Related Problem in Reference Coder(JM9.3)

[Kim, Hee-yong]

Dear all,
I have decoding failure while doing encoding and decoding the following:
------------------------------------------------------------------------
--------------------
Picture size: 720x576 (4:2:2)
Video: Mobile
Frame Rate: 25 Hz
Profile: 122
Level: 40
Picture Structure: IBBPBBPBBPBBI
IDRIntraEnable:0 (Intra Picture is not IDR picture except 1st)
BreferncePicture:1  (B frame is reference frame)
PictureInterlace: 2 (Adaptive Frame/Field)
MbInterlace: 2 (Adaptive Frame/Field)
SymbolMode: 1 (CABAC)
NumberReferenceFrames: 5
------------------------------------------------------------------------
-------------------------
I did encoding and decoding.
During decoding, there was a Segment Violation in the middle 
by referecing frame number 5 which is NULL pointer
and is out of DPB if it is a frame based prediction.
I encoded and decoded  twice to make sure this and they were same.
I used DDD and at least I know where it was, but could not nail down all
the way.
However, I did not have a problem when I encoded with CAVLC.
So, I think that it is probably related to CABAC.
I wonder that anyone had the similar problem I had and please let me
know.
Also when I look at the code, 'read_one_macroblock()' in "image.c", it
is hard to follow by H.264 syntax.
It is probably equivalent code but I wish it follows the syntax as much
as possible.
Also, the notation is not the same as H.264.
For example, skip_flag  in the macroblock seems to be used the other way
around.
By syntax, skip_flag=1 means that MB is skipped, but the code negates
the bits.
Also, MB_type is at first assigned to skip_flag when it reads skip_flag
,
and then later it is overwritten when it really reads MB_type.
Regards,
Hee-Yong Kim
Hee-yong.kim cinea.com
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