[Mp4-tech] [H.264] Deblocking across Slices/SliceGroups

[John Cox]

Hi
Yes, when disable_deblocking_filter_idc=0 then you have to filter across
slice boundaries.  I can't speak for the standards committee, but I rate
the picture quality gains achieved by deblocking across the slice
boundaries as outweighing the minor corruption of edge pels under error
conditions (as you have clearly lost the slice 'above' then this is
trivial in comparison).  If it does worry you then you should use
deblocking_filter_idc=2 (and probably constrained_intra_pred_flag=1
too).
Regards
John Cox
SJ Consulting
>Hello All,
>
>I have some confusion regarding the Deblocking specifications. The
>specifications [Ref: ITU-T Rec. H.264 (03/2005) - Prepublished version]
>in Section 8.7, say that when  "disable_deblocking_filter_idc is equal
>to 2, macroblocks in different slices are considered not available
>during specified steps of the operation of the deblocking filter
>process." It also mentions that
>filterLeftEdgeMBFlag/filterTopEdgeMBFlag=0 when
>disable_deblocking_filter_idc =2 and mbAddrA/mbAddrB is not available.
>Since 'availability' (Section 6.4.5) is defined to treat macroblocks in
>different slices as not available, this means that when
>disable_deblocking_filter_idc =2 we do not have to apply the filter
>across slice edges. Some questions:
>
>~ What about the case when disable_deblocking_filter_idc =0? Do we have
>to filter across slices in this case? Doesn't this conflict with the
>fundamental idea behind slices (error resilience)?
>~ What about sliceGroups? Since every sliceGroup edge will necessarily
>be a slice edge, does the above apply to sliceGroup edges too? 
>
>
>Thanks and regards,
>Mohit Garg
>Nvidia Graphics Pvt. Ltd.
>
>"We may say that we KNOW, but by our actions it is KNOWN" -- Anon
>Personal Homepage: http://mohitgarg.vectorstar.net
>Social Work: http://www.noragging.com
>
>