[Mp4-tech] DC Parameter In Chroma Residue Computation and Run-Level Coding in H.264

[Sugeeth]

Hi Friends,
                 I have a doubt and hope that some of you would be able 
to reply back to me regarding this issue.
The doubt is with only  Reference to P frame  Processing and not I frames :
In H.264, during luma coding, all values in the 4x4 block are taken as 
ACvalues and the AClevels and ACruns are computed.
There is no DC parameter in Luma.
1.However, in chroma, we take the first pixel of each 4x4 block, combine 
the 4 such pels of a U or V 8x8 block and seperately process these 
values as hadamard's and the run- level coding done for these 4 values 
stored seperately in a DC Array while the remaining 15 pixels in each 
4x4 chroma block is processed as AC... Why this differentiation that 
only Chroma should only contain DC Components and Luma does not contain 
DC Components....... ????.
2. Since the eye is sensitive  to luma and very less to chroma, with 
some minor degree of error, can we code the DC pels in the Chroma Blocks 
as AC itself, or does such a change deviate away from the H.264 
standard?????
Thank you,
Sugeeth.