[M4IF Technotes] Request for clarifications while decoding backward using RVLC

[A.Ilangovan]

Dear friends,
1)   For RVLC backward decoding also, we require the
      DC values of Ref blocks "A" and "C". To be assured of these
      Ref Blocks' DC values in the data_partitioned (DP) header,
      only the DC VLC table must be used and AC VLC table must
      not be used (If AC VLC table is used for DC coef, the DC is
      treated with other AC coeffs in the texture info and would have
     got corrupted in errors and also not available in DP header).
     The safer / simpler way to ensure this is to make "intra_dc_vlc_thr"
      equal to "0" in VOP header (ofcourse in VP header also), which
     always forces the DC VLC table for DC coefficients of all the blocks.
     To the extent I tried to confirm this from the standard, I am not able
     to find it. Am I missing it or it is missed in the standard? However,
     all the test bitstreams provided by the standard has "intra_dc_vlc_thr"
     equals "0" in such cases. But, I don't want to infer this way, and may
     I request confirmation from experts? Also, if this is the true and is
not
     mentioned in the standard, it should be added in the amendments to
    avoid this ambiguity.
2)  This confusion can be further fuelled by E.1.4.4.2.2 (page:425) which
     says INTRA MBs in a DP VP must be discarded even though they
     could have been decoded!
    Again, I have infered from the context that, this is applicable for
    INTRA MBs in P-VOPs only!! Can experts confirm this also?
    If this is also correct, one more item for amendments?
Thank you in advance
A.Ilangovan
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