Databases Reference
In-Depth Information
(a)
(b)
(c)
F I GU R E 16 . 3
Three popular subband structures.
F I GU R E 16 . 4
Decomposition of Sinan image using the four-tap Daubechies filter.
If we now encode this image at the rate of 0.5 bits per pixel, we get the reconstructed
image shown in Figure
16.5
. Notice that the quality is comparable to that obtained using filters
requiring two or four times as much computation.
In this example, we used a simple scalar quantizer for quantization of the coefficients.
However, if we use strategies that are motivated by the properties of the coefficients themselves,
we can obtain significant performance improvements. In the next sections, we examine two
popular quantization strategies developed specifically for wavelets.
