JPEG - Idea and Practice/Appendix 1: Summary of the header segments

DQT (quantization)

Marker = (255, 219)

Length = (0, 67)

0 (½ byte)

destination identifier (½ byte)(for instance 0 for the Y component and 1 for the colour components)

the table (64 bytes)

SOF (frame)

Marker = (255, 192)

Length = (0, 8 + 3 * number of components)

8

width = b1*256 + b2, pair (b1, b2)

height = b1*256 + b2, pair (b1, b2)

number of components (1-3)

for each component:

component identifier (for instance 0, 1, 2 for the YCbCr components)

Hi (½ byte)(1 for the colour components, 1 or 2 for the Y component)

Vi (½ byte)(1 for the colour components, 1 or 2 for the Y component)

quantization table destination selector (for instance 0 for the Y component and 1 for the colour components)

DHT (Huffman)

Marker = (255, 196)

Length = (0, 19 + number of Huffman values (nhv))

0 for DC, 1 for AC (½ byte)

destination identifier (½ byte)(for instance 0 for the Y component and 1 for the colour components)

the list BITS (16 byte)

the list HUFFVAL (nhv bytes)

SOS (scan)

Marker = (255, 218)

Length = (0, 6 + 2 * number of components)

number of components (1-3)

for each component:

component identifier (for instance 0, 1, 2 for the YCbCr components)

destination selector of DC Huffman table (½ byte)(for instance 0 for the Y component and 1 for the colour components)

destination selector of AC Huffman table (½ byte)(for instance 0 for the Y component and 1 for the colour components)

0

63

0