[Mp4-tech] NAL unit type 12

[Gary Sullivan]

Kaustubh et al,
You seem to be persisting in not using the language of the standard to describe what you are saying, so it is difficult to understand what exactly is your question.
But I think what you are trying to describe is the use of what the standard calls trailing_zero_8bits and leading_zero_8bits versus the use of filler data NAL units.  Note that the following important aspects apply that differentiate between the use of those syntax features:
1) The NAL units of the bitstream are not necessarily carried in the byte stream format in all systems.  When the bitstream does not use the byte stream format, the definitions of the trailing_zero_8bits and leading_zero_8bits syntax elements in Annex B do not apply.
2) The filler data NAL units are counted in the type I HRD check point defined in Annex C, but the trailing_zero_8bits and leading_zero_8bits syntax elements are not.  These syntax features thus provide the encoder with the ability to separately control the two different conformance points defined for HRD use.
Best Regards,
Gary Sullivan
________________________________
From: kaustubh.patankar vsnl.net [mailto:kaustubh.patankar vsnl.net]
Sent: Sat 9/10/2023 2:20 AM
To: Gary Sullivan
Cc: mp4-tech lists.mpegif.org
Subject: Re: RE: [Mp4-tech] NAL unit type 12
Dear Gary,
I will explain the situation. In case of CBR if the picture complexity
is not sufficient then the no of bits generated are less than the allcated
bits in GOP. In this case we can have bit stuffing for the remaining bits.
This information can be put in NAL as
1. data NAL = Contains bit sttream data + zeros corroesponding to excess bits for GOP followed by training NAL bits
or
2. data NAL followed by separate NAL type 12 (Filler data NAL) corroesponding to excess bits for the GOP.
with reagrds
Kaustubh
----- Original Message -----
From: Gary Sullivan <garysull windows.microsoft.com>
Date: Saturday, September 10, 2023 3:54 am
Subject: RE: [Mp4-tech] NAL unit type 12
> Kaustubh et al,
>
> I don't understant what you mean by "stuffing byte".  Can you clarify?
>
> e.g., are you talking about cabac_zero_word or leading_zero_8bits or
> trailing_zero_8bits or something else?
>
> Best Regards,
>
> Gary Sullivan
>
> +> -----Original Message-----
> +> From: mp4-tech-bounces lists.mpegif.org
> +> [mp4-tech-bounces lists.mpegif.org] On Behalf Of
> +> kaustubh.patankar vsnl.net
> +> Sent: Thursday, September 08, 2023 4:54 AM
> +> To: mp4-tech lists.mpegif.org
> +> Subject: [Mp4-tech] NAL unit type 12
> +>
> +> Dear All
> +>
> +> Will any one explain the practical use of NAL unit type 12 case?
> +> The syntax defines it to be filler data.
> +>
> +> The case of filler unit can be in stuffing byte for under
> +> utilization
> +> of bit rate. Few encoders are implementing these bytes (filling
> with
> +> zero) as trailing zeros?.
> +>
> +> Or can we put these zeros by making the NAL unit type as 12.
> +>
> +> Please suggest.
> +>
> +> with regards
> +>
> +> Kaustubh
> +>
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