The transform itself is often of a small block rather than the entire macroblock.

Figure 1: An example of macroblock assignment to four slices.

A macroblock is the smallest independent unit of (color) video.

A predicted macroblock rarely matches the current picture perfectly, however.

Different reference frames can be chosen for each 8x8 partition of a macroblock.

In the worst case, swapping occurs after decoding each macroblock.

Motion vectors (see below) operate solely at the macroblock level.

The differences between the estimated matching area, and the real frame/macroblock is called the prediction error.

The encoder will only record that it is a Skip Macroblock.

This choice, while costing an additional bit per macroblock, can improve prediction quality and therefore reduce residual.

Scattered or dispersed slice groups, type 1: Every macroblock is a different slice.

P-frames have 1 motion vector per macroblock, relative to the previous anchor frame.

Only the (smaller) amount of difference between the MVs for each macroblock needs to be stored in the final bitstream.

A possible bitstream representation of a macroblock in a video codec which uses motion compensation and transform coding is given below.

This allows the video encoder to choose among more than one previously decoded frame on which to base each macroblock in the next frame.

The basic processing unit of the design is called a macroblock, and H.261 was the first standard in which the macroblock concept appeared.

Partial macroblocks, and black borders/bars encoded into the video that do not fall exactly on a macroblock boundary, cause havoc with motion prediction.

Then, the macroblock is treated like an I-frame macroblock.

The difference between a P-frame and its anchor frame is calculated using motion vectors on each macroblock of the frame (see below).

Macroblock is a processing unit in image and video compression formats based on linear block transforms, such as the discrete cosine transform.

The sequence and picture parameter set structures contain information such as picture size, optional coding modes employed, and macroblock to slice group map.

The list of pointers, together with the address of the first macroblock of the slice, will be used to navigate through the out of order slices.

This "residual" is appended to the motion vector and the result sent to the receiver or stored on the DVD for each macroblock being compressed.

In H.265/HEVC, the macroblock as basic processing unit been replaced by the coding tree unit.

These boundaries can be transform block boundaries, prediction block boundaries, or both, and may coincide with macroblock boundaries.