Parameters other than the splitting level and the common mode parameter are, perhaps confusingly, termed block data, even though they may apply to blocks, sub-MBs or the MB itself depending on the value of the MB data. The prediction mode has already been described. The five remaining block parameters are:
REF1_x: horizontal component of motion vector to the first reference frame;
REF1_y: vertical component of motion vector to the first reference frame;
REF2_x: horizontal component of motion vector to the second reference frame;
REF2_y: vertical component of motion vector to the second reference frame.
DC: DC or average value for the prediction unit for each component (Y, U or V) being coded, to 8-bit accuracy.
Clearly not all of these values must be coded. If the prediction mdoe is REF1_ONLY then REF2_x and REF2_y will not be coded, for example, and if the prediction unit is not INTRA, then no DC value need be sent.
Previous: Variable size block-matching
Table of contents Back to Macroblock structures and motion vector data