[M4IF Technotes] Short Video Header mode problem

[Luc Martel]

Hi all,
This migth be a simple problem but I've been banging my head on it since few
days and I still don't understand what's going on. I'm encoding in Short
Video Header mode at 30 (29.97) fps, so that my temporal_reference field
increment by one every frame (I tried to keep it simple). I'm encoding every
frame in only 1 group of blocks (again, I kept it simple). In the first
group of picture (in the first IPPPPPPPPPPP group) there is no problem. The
problems start after this first group of pictutre. For some reason it look
like the decoder gets confused and don't use the right reference frame.
I don't know if there is something that I'm not doing right or not doing at
all. For every frame, in video_plane_with_short_header(), I increment
temporal_reference by one, set the picture_coding_type to either (0 for I, 1
for P) and the macroblocks are following. The other fields don't seem to be
related with the synchronisation.
I didn't know whether I could post a bit stream example in attachment. But I
have a 5 seconds example, foreman 30fps, 100 P-frames per GOP. The first GOP
is perfect but in the second you can easily see that something is wrong.
Tkx in advance.
Luc Martel
Senior Engineer
Atsana Semiconductor Corp.
lmartel   atsana.com