Image Processing Reference
Logarithmic scaling of samples
Figure 13-2 Logarithmic quantization.
Predictive Coding Improvements
The H.264 codec adds a spatial predictive tool for macroblocks within the same slice.
Prediction allows the starting point of a macroblock to be based on an earlier block with
only the residuals described as a series of changes to apply. This is slightly more efficient
than simply defining an average color value since some kind of gradient across the mac-
roblock might be usefully applied to make the residuals much smaller.
The prediction within a 16
16 macroblock is applied to the 4
4 sub macroblocks
16 macroblocks are
predicted based on a block from earlier in the same slice and several modes are used to
define how the prediction is applied.
and is based on an earlier block to the left and above. Complete 16
H.264 adds a very useful postprocessing step that softens the artifacts caused by over-
quantization. This artifact is exhibited as a very blocky appearance where the macroblock
structure of the image shows through.