Macro Blocking

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A block is an 8x8 pixel area of the image, and thus is 64 pixels. A macro-block is 4 intensity blocks plus 2 color blocks (Pr and Pb), and thus is a complete representation of a 16x16 area. (It gets more complicated for interlace.)

Macro blocking is when the macro-block boundaries become evident. There are two common situations when this happens. 1. A reception error can cause macro-blocks to become lost or misplaced in the image. 2. In high action scenes the required data rate can exceed what is allowed. There are several software schemes for dealing with this. One is to randomly delete (defer) macro-blocks. Another is to reduce resolution momentarily. Both of these can make the macro-block boundaries evident, especially if you sit close.