Cirrus Logic's format packs 4 pixel samples into a single u_int32 by sacrificing precision on each sample. Y samples are truncated to 5 bits each, U and V have 6 bits per sample.
|Y Sample Period||1||1|
|V Sample Period||4||1|
|U Sample Period||4||1|
Effective bits per pixel : 8
Positive biHeight implies top-down image (top line first)