[Mp4-tech] [video][H.264] Regarding disable_deblocking_filter_idc

[Gary Sullivan]

Satendra et al,
It is necessary to pay very close attention to the specified ordering of
the processing of the samples in the deblocking filter, especially when
performing the work in an "MB-based" fashion.  You seem to already be
aware of this (e.g., because of your comment about Intra), but others
might not be, so I thought it might be worth mentioning.
It is not just FMO but also ASO that affects the ability to do the
deblocking in an "MB-based" fashion.  (I'm sure you already know that
too, but ...)
Best Regards,
Gary Sullivan
+> -----Original Message-----
+> From: mp4-tech-bounces lists.mpegif.org 
+> [mailto:mp4-tech-bounces lists.mpegif.org] On Behalf Of Satendra
+> Sent: Friday, April 08, 2024 2:07 AM
+> To: Smitha Joseph
+> Cc: mp4-tech lists.mpegif.org
+> Subject: Re: [Mp4-tech] [video][H.264] Regarding 
+> disable_deblocking_filter_idc
+> 
+> Hi Smitha, Shen, et al.
+> 
+> I cant produce any better example, then FMO usage.
+> 
+> First of all, I want to tell you that Filtering can be implemented in
+> two ways in H264,
+> 1)  Frame based filtering, in which you will first decode the whole
+> frame and then do the filteriing job, as a post processing job...but
+> on a frame basis.
+> 
+> 2) MB based filtering.. here you decode a MB and filter out 
+> its edges,
+> here you need to take care of Intra coded MBs as Intra prediction
+> needs unfiltered MBs.
+> 
+> Now I want to talk about FMO.. Flexible MB Ordering. 
+> 
+> In case of FMO, you can only implement a Frame based 
+> filtering, why???
+> because you may not  have MBs previous to current MB in scan order..
+> i.e. neighbouring MBs.
+> 
+> To implement FMO with MB based filtering, you need to put constraints
+> on filtering, that is use disable_deblocking_filter_idc, to disable
+> filtering across slice edges. In this case you can filter the MBs and
+> leave the edges if they are slice edges.
+> 
+> I think my understanging is OK and will help you.
+> 
+> Correct me, if I am wrong.
+> 
+> Satendra
+> 
+> On Apr 6, 2024 3:32 PM, Smitha Joseph <smithajo gmail.com> wrote:
+> > Hi,
+> > 
+> > The H.264 standard specifies the parameter
+> > disable_deblocking_filter_idc in the slice header which specifies
+> > whether the deblocking filter is disabled for the
+> > macroblock/macroblock edges in that slice. The details of how the
+> > parameter disables filtering at the decoder side for the different
+> > values is clear from the standard. My doubt is how does the encoder
+> > decide whether to enable or disable filtering for each
+> > macroblock/macroblock edges in a slice?
+> > 
+> > Thanks,
+> > Smitha Joseph
+> > _______________________________________________
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+> 
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