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:

  1. The tile for frame #1 is encoded as an original tile at 25% progressive quality.

  2. The tile is upgraded to 50% progressive quality.

  3. The tile for frame #2 is encoded as a difference tile at 25%.

  4. The tile is upgraded to 50%.

  5. 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