[M4IF Technotes] question about the value of fixed_vop_time_i ncrement

[Kris Huber]

Hi Leonid and Amit,
This problem in the text is corrected in an upcoming MPEG-4 corrigenda item
under ballot.  Please inform the list if this text does not match the
behavior of both reference software versions dated 12/2000 and beyond, which
is the intent in this particular case (in earlier reference software,
Microsoft used 0 bits and MoMuSys used 1 bit for vop_time_increment in the
case of vop_time_increment_resolution=1).
vop_time_increment:  This value represents the absolute vop_time_increment
from the synchronization point marked by the modulo_time_base measured in
the number of clock ticks. It can take a value in the range of
[0,vop_time_increment_resolution). The number of bits representing the value
is calculated as the minimum number of unsigned integer bits required to
represent the above range, unless vop_time_increment_resolution is equal to
'1', in which case one bit with a value of '0' is used. The local time base
in the units of seconds is recovered by dividing this value by the
vop_time_increment_resolution.
modulo_time_base:  This value represents the local time base in one second
resolution units (1000 milliseconds). It consists of a number of
consecutive '1' followed by a '0'. Each '1' represents a duration of one
second that have elapsed. For I-, S(GMC)-,  and P-VOPs of a non scalable
bitstream and the base layer of a scalable bitstream, the number of '1's
indicate the number of seconds elapsed since the synchronization point
marked by time_code of the previous GOV header or by non-zero
modulo_time_base of the previously decoded I-, S(GMC)-, or P-VOP, in
decoding order. For B-VOP of non scalable bitstream and base layer of
scalable bitstream, the number of '1's indicate the number of seconds
elapsed since the synchronization point marked in the previous GOV header,
I-VOP, S(GMC)-VOP,  or P-VOP, in display order. For I-, P-, or B-VOPs of
enhancement layer of scalable bitstream, the number of '1's indicate the
number of seconds elapsed since the synchronization point marked in the
previous GOV header, I-VOP, P-VOP, or B-VOP, in display order.
I think this matches what Chris Lampert indicated as well.
Regards,
Kris Huber
-----Original Message-----
Date: Tue, 1 Oct 2023 19:36:49 +0300
From: "Amit Klir" <amit.klir   emblaze.com>
To: <technotes   lists.m4if.org>
Cc: "Leonid Kolotigin" <leonid.kolotigin   emblaze.com>
Subject: [M4IF Technotes] question about the value of
fixed_vop_time_increment
Hi,
We have a question regarding the number of bits for the representation of
VOP_time_increment_resolution
where its value is 1.
In the case of  vop_time_increment_resolution == 1  and fixed_vop_rate == 1
the sending of the bit for the fixed_vop_time_increment is redundant.
the only possible values of the vop_time_increment and
fixed_vop_time_increment are in the range of
[0,VOP_time_increment_resolution).In this case
the value is 0.
If we have the value of the VOP_time_increment_resolution == n , we need n-1
bits for the vop_time_increment representation.
In this special case the number of bits for the fixed_vop_time_increment is
0.
According the standard, what is the actual number of bits that need to
specify the case of  VOP_time_increment_resolution=1 
	0 - since 0 is the minimum between [0 1) ?
or 
	1- since the value 0 is forbidden ?
Thanks in advance
 Leonid & Amit
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