[Mp4-tech] minimum # of slices

[Ahmed, Syed Mahmood]

Tomo San,
U once asked a similar question on the "maximum number of slices" per picture
Below, I copy-paste your original question on that subject, and Mr. Gary Sullivan's reply to your question. I want to take this opportunity to revisit that discussion
In his reply to your question on maximum number of slices per picture , Gary seems to suggest that the "SliceRate" (as provided in Table A-4, page 265 of the spec) provides an upper limit (max value) for the long-term average of the number of slices per picture.  
However, the spec in Section A.3.3, on page 263 says: 
"...shall satisfy  the constraint that the number of slices in picture n is less than or equal to MaxMBPS * ( tr( n )   tr( n   1 ) ) ÷ SliceRate ...".  
For Main Profile, Level 3, for PAL, the above calculates to 40500 * 0.04 / 22 = 73.6. 
It looks to me like the SliceRate is more like a constraint on the minimum number of macroblocks per slice 
I'll appreciate your feedback
Thanks
>[Mp4-tech] [H.264, VIDEO] maximum number of slices
>Gary Sullivan garysull windows.microsoft.com 
>Wed Mar 28 19:27:56 EDT 2007 
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>Tomo,

>That is almost true, but not quite true.  The the number of allowed slices increases if >the decoder is given more time to decode a picture (as measured by the difference >between decoding times, i.e., between CPB removal times).

>If fixed_frame_rate_flag is 1 (so the sequence is fixed at the maximum frame rate >which in this case is 25 fps at 720x576 picture size), then it is true that the *average* >number of slices per picture over a (very) long period of time cannot exceed 22.  But >there's a difference between talking about the average over time and talking about >the limit on any particular picture.

>The constraint is imposed on a per picture basis, based on the amount of time >between decoding timestamps (CPB removal times).  For that picture size 
> (720x756), the decoding times of frames can't be closer together than 1/25th of a >second (for level 3).  But if the decoding times are farther apart, the number of >allowed slices for the picture increases.

>The limit is really more time-based than picture-based.

>Best Regards,

>Gary Sullivan 

+> -----Original Message-----
+> From: mp4-tech-bounces lists.mpegif.org 
+> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Tomo
+> Sent: Wednesday, March 28, 2024 1:38 PM
+> To: mp4-tech lists.mpegif.org
+> Subject: [Mp4-tech] [H.264, VIDEO] maximum number of slices
+> 
+> Hi
+> 
+> I was told that (Main profile, Level 3) bitstream can have
+> 22 slices (maximum) per frame.
+> Is that correct?
+> 
+> Standard limits "slice rate" to 22 for this level and profile.
+> But I do not think the slice rate == the number of slices per frame.
+> 
+> So, in case PAL/NTSC (D1) rate sources, what will be the maximum
+> number of slices per frame?  Or is it indeed 22?
+> 
+> Also, somewhat relating question. Are there any NAL size limitation?
+> Can a NAL be 600Kbits?  [600K is arbitrary I picked). 
+> 
+> Thanks
+> 
+> 
+> Tomo
-----Original Message-----
From: mp4-tech-bounces lists.mpegif.org [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Tomo
Sent: Thursday, July 19, 2023 5:15 PM
To: mp4-tech lists.mpegif.org
Subject: [Mp4-tech] minimum # of slices
Hi
In case MPEG2, a picture cannot be composed of a slice (assume picture
hight is more than 16-pixel).  In case H.264 standard, as far as
Iknow, there is no such restrictions (a picture can be a slice).
I have been thinking how to design HD-resolution decoder within
reasonable design technology, cost and so forth. For MPEG2, I
once designed HD-decoder to implement multiple slice-level decoders
(slice-level decoder can handle picture-level, so 1 HD decoder can
handle multiple SD-level streams in parallel). This worked quite
good.  In case H264, even slice is a good boundary, since a picture
may be composed of one slice, I cannot use the technique.
Then, I wondered, if any product specifications (e.g. HD-DVD, Bluray)
that utilize H264 have certain restrictions. So far I do not find any,
though I found some service prohibits using FMO, ASO and other
features that H264 standard specifies. 
So, even though it may not be a good question to ask, are there
any restrictions in specification (not in H264 standard) discussing
the number of slices per picture?
HD-level decoder design is quite a challenge (H264). Regardless
of the slice structure, deblock filter also makes some difficulty
as de-block filter can accross the slice boundary. 
But there seems already some HD-level decoders, but design itself
is not much discussed.  If someone can point me any papers or
publications, much appreciated. 
Regards
Tomo