4.1.2 Progressive Entropy Encode and Decode
The example in this section illustrates the process of entropy encoding and decoding for a tile at various quality levels. For simplicity, this example only encodes one color component, which consists of 14 DWT coefficients.
The tile contains three bands: HL, LH, and LL. These bands are composed of 5, 5, and 4 DWT coefficients, respectively, totaling 14 coefficients for the tile.
Three progressive quality levels are used when encoding: 25%, 50%, and 100%.
The input presented in this example is the direct result of the discreet wavelet transform and quantization of a sample image.
The following scenarios are covered in this example:
The tile for frame #1 is encoded as an original tile at 25% progressive quality.
The tile is upgraded to 50% progressive quality.
The tile for frame #2 is encoded as a difference tile at 25%.
The tile is upgraded to 50%.
The tile is finally upgraded to 100%.
The coefficients for frame #1 and frame #2 are presented in the following table.
|
|
HL |
LH |
LL |
|||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
Frame #1 |
-34 |
-13 |
15 |
-3 |
0 |
0 |
-7 |
5 |
-3 |
9 |
15 |
17 |
-9 |
12 |
|
Frame #2 |
-2 |
-2 |
3 |
-3 |
1 |
3 |
-7 |
5 |
-2 |
1 |
24 |
13 |
18 |
5 |
The progressive quantization table for the two intermediate qualities (25% and 50%) appear in the following table.
|
Quality |
HL |
LH |
LL |
|---|---|---|---|
|
25% |
4 |
3 |
2 |
|
50% |
0 |
1 |
2 |