Decoding a JPEG Huffman block (table)

Question

The following block is nested by Huffman block markers

-HUFF---------------------------------------------------------------------0084-
  10    0    1    2    4           


        

Answer 1

The next 16 bytes after the 0x10 tell you how many codes of each length. In your example, there are 0 codes of length 1 bit, 1 code of length 2 bits, 2 codes of length 3 bits, 4 codes of length 4 bits, 3 codes of length 5 bits, and so on.

These are then followed by the values that are encoded by those codes, in order. Again from your example:

Code length | Number | Symbol(s)
------------+--------+----------
1 bit       | 0      |
2 bits      | 1      | 0x01
3 bits      | 2      | 0x02 0x11
4 bits      | 4      | 0x00 0x03 0x04 0x21
5 bits      | 3      | 0x05 0x12 0x31
... etc

You then build a binary tree from the top down, assigning the symbols in order. In this example, you get:

Symbol | Code 
-------+------
0x01   | 00
0x02   | 010
0x11   | 011
0x00   | 1000
0x03   | 1001
0x04   | 1010
0x21   | 1011
...etc