[M4IF Technotes] Short Video Header

[Nitin Gupta--DSP, Noida]

Hi all,
	I have some doubt regarding the short video header
streams in Mpeg4. 
1) There is a parameter in the video plane with short header
"source format" which tells about the width & height of the
plane represented by the video_plane_with_short_header. I want to 
know can this parameter change within a particular stream 
between different frames ??
2) There is a parameter called "gob_frame_id" in the video plane
with short header. The description given about this parameter in
the standard 14496-2 on page no 129 is as follows :-
****
gob_frame_id:  This is a two bit field which is intended to help determine
whether the data following a gob_resync_marker can be used in cases for
which the vop header of the video_plane_with_short_header() may have been
lost. gob_frame_id shall have the same value in every GOB header of a given
video_plane_with_short_header(). Moreover, if any field among the
split_screen_indicator or document_camera_indicator or
full_picture_freeze_release or source_format or picture_coding_type as
indicated in the header of a video_plane_with_short_header() is the same as
for the previous transmitted picture in the same video object, gob_frame_id
shall have the same value as in that previous
video_plane_with_short_header(). However, if any of these fields in the
header of a certain video_plane_with_short_header() differs from that in the
previous transmitted video_plane_with_short_header() of the same video
object, the value for gob_frame_id in that picture shall differ from the
value in the previous picture.
****
The last 2 statements seem to be confusing. Is the last statement 
enough for the description ??
Thanx for ur cooperation.
Regards,
Nitin.