[M4IF Technotes] About getting time_stamp from the vops

[Li Zhengming]

Hi all!
I have a question about the time codes in the vops. I figured the modulo_time_base and vop_time_increment in a video stream coded with xvid, which is without B vops, and found that the modulo_time_base is always 0, while the vop_time_increment is always 1. This is not to understand, since the Mpeg4 video specification says that vop_time_increment indicates the time increment of the current vop compared with the previous I or P vop in display order.
I think this is consistent with the spec. 
However, I found another kind of pattern when I was looking for information about the vop_time_increment in the M4IF technotes library, which was as follows:
It seems that every vops have the first I vop as their reference vop, and have incremental vop_time_increment values:10, 20, 30, and so on. I wonder whether this is reasonable according to the Mpeg4 video spec, and when this kind of time code patter can exist should it be reasonable and valid.
Thanks for your consideration!
THE FOLLOWING IS WHAT I SAW IN A TECHNOTES::
That is what I expected, fine. However, this is just for
> I/P/S-VOPs, not
> for B-VOPs. Consider almost a sequence encoded with IBBPBBPBBP...
> and only 12fps to keep the lines shorter (vop_time_incr_res=120),
> I understand it would be (display order):
>
>  I   B   B   P   B   B   P   B   B   P   B   B   P   B   B   P
>  0   0   0   0   0   0   0   0   0   0   0   0   1   0   0   0
> 000 010 020 030 040 050 060 070 080 090 100 110 000 010 020 030
>
> now with 11fps (vop_time_incr_res=110) things get complicated.
> Would it be:
>
>  I   B   B   P   B   B   P   B   B   P   B   B   P   B   B   P
>  0   0   0   0   0   0   0   0   0   0   0   1   1   0   0   0
> 000 010 020 030 040 050 060 070 080 090 100 000 010 020 030 040

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