[Mp4-tech] Non zero Coefficients in deblocking filter

[rama krishnan]

Hello Experts,
I am a beginner and working on JSVM 9.6, can you please tell me where (in
which file) I have to change/modify to get output of different size of
pictures that can be viewed on any player.(In short by what means I can
achieve spatial or temporal scalable output).
Please help the beginner.
Waiting for your responses and helpful links.....
Thanks in advance.
On Tue, Apr 22, 2024 at 8:09 AM, Gary Sullivan <
garysull windows.microsoft.com> wrote:
>  It is true that the CBP is an 8x8-level indicator while the transform
> block size is sometimes smaller.  However, we have some significant
> constraints on the relationship between coded block pattern and the presence
> of non-zero transform coefficients.  My recollection is that the reasoning
> behind those restrictions is to allow the checking of the coded block
> pattern as a substitute for some of those conditions and that this is what
> the reference software decoder does (or at least did at one time).  I
> think that was for deblocking filter purposes.
>
> Referring to the JVT-X201 draft, see subclause 7.4.5 below equation 7-34,
> up to and including Table 7-15.  There are some constraint statements using
> the word "shall" there that would not be necessary if we weren't trying to
> use the CBP for some non-obvious purpose.  Those are there for that reason. There
> is a long history on that topic.
>
> Best Regards,
>
> Gary Sullivan
>
>  ------------------------------
> *From:* Jain, Anurag [mailto:anurag ti.com]
> *Sent:* Tuesday, April 22, 2024 6:41 AM
> *To:* Gary Sullivan; Srikar Dasari; mp4-tech lists.mpegif.org
>
> *Subject:* RE: [Mp4-tech] Non zero Coefficients in deblocking filter
>
>    Gary,
>
>
>
> Doesn't CBP come at 8x8 block level and Total Coefficients come at 4x4
> sub-block level. Boundary strength is calculated for sub-block edges so
> Total Coefficients is a more appropriate measure to check. Hence CBP bit can
> be non-zero and still some of the sub-blocks may have all-zero coefficients.
>
>
>
> I think we need to check Total Coefficients and derive CSBP (Coded
> Sub-Block Pattern) for loop filtering.
>
>
>
> Regards,
>
> Anurag
>
>
>  ------------------------------
>
> *From:* mp4-tech-bounces lists.mpegif.org [mailto:
> mp4-tech-bounces lists.mpegif.org] *On Behalf Of *Gary Sullivan
> *Sent:* Tuesday, April 22, 2024 9:28 AM
> *To:* Srikar Dasari; mp4-tech lists.mpegif.org
> *Subject:* RE: [Mp4-tech] Non zero Coefficients in deblocking filter
>
>
>
> Srikar,
>
>
>
> I suggest to check what the reference software is doing.  If I remember
> correctly, the text is phrased so that certain things are prohibited (by
> disallowing the values of all transform coefficients being decoded as zero
> when some coded block pattern bits are set), so that the complexity of the
> decoding process is minimized.  The text and software do the same thing, but
> that is not obvious at first glance, because their equivalence depends on
> the exact phrasing of the text.  We had one or two correction efforts
> devoted to this topic in the past, so if you look in some old drafts you
> will find incorrect text.
>
>
>
> Again, my basic advice is to check what you find in the JM reference
> software.
>
>
>
> Best Regards,
>
>
>
> Gary Sullivan
>  ------------------------------
>
> *From:* mp4-tech-bounces lists.mpegif.org [
> mp4-tech-bounces lists.mpegif.org] On Behalf Of Srikar Dasari [
> srikar pelican-networks.com]
> *Sent:* Monday, April 21, 2024 3:43 PM
> *To:* mp4-tech lists.mpegif.org
> *Subject:* [Mp4-tech] Non zero Coefficients in deblocking filter
>
> Experts,
>
>
>
> I have a question in the boundary calculation in deblocking filter. I kinda
> of asked this question earlier. I need some more clarification.
>
> In the filtering process the boundary strength is set based on one of the
> conditions being, the luma block p0 or luma block q0 contains non-zero
> transform coefficient levels.
>
>
>
> My question is,
>
> Isn't this non-zero transform coefficient level condition, come from both
> CBP value and also from the TC (total coefficients) during the CAVLC
> decoding?
>
> In other words, Do we have to consider the CBP pattern alone or Do we have
> to take into account TC being zero, in addition to CBP.
>
>
>
> Please let me know, if I am not clear anywhere. Your answers are greatly
> appreciated.
>
>
>
> Thanks,
>
> Srikar
>
>
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