motion estimation and compensation for very low bitrate video coding

26 Chapter 1. Digital Video Coding at Very-Low BitRate
Watershed
computation
original
image tree
A
decomposition
B
C
regions
labels
interest
criteria
merge
procedure
interest
labels
D
reconstruction
E F
Figure 1.5: Block diagram to intra-code a picture in the COMIS coder
components by a succession of binary decisions. A binary tree ensures
the correspondence with a multiscale representation of the picture (Figure
1.6).
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1
1 1
1
0 0
1 0
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1
1
1 0
0 1
1 0
0 1
Figure 1.6: Example of binary tree segmentation
The split process is repeated until reaching homogeneous blocks or a
block of prede ned minimal size. Once the block is considered homogeneous
enough, the luminance of all its pixels is replaced by the mean
luminance of the block (plus midtread quantization) and is attached to
the appropriate leaf of the tree. A criterion (see references) is added
to prevent regions with random textures from splitting. Such regions
are assumed not to be perceptually important and are also described by
their mean value.
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