TABLE OF CONTENTS Figure 13.5 illustrates the video bitstream, a hierarchical structure with seven layers. From top to bottom the layers are:
Video Sequence
Sequence Header
Group of Pictures (GOP)
Picture
Slice
Macroblock (MB)
Block
Several extensions may be used to support various levels of capability. These extensions are:
Sequence Extension
Sequence Display Extension
Sequence Scalable Extension
Picture Coding Extension
Quant Matrix Extension
Picture Display Extension
Picture Temporal Scalable Extension
Picture Spatial Scalable Extension
If the first sequence header of a video sequence is not followed by an extension start code (000001B5 H), then the video bitstream must conform to the MPEG-1 video bitstream.
For MPEG-2 video bitstreams, an extension start code (000001B5 H) and a sequence extension must follow each sequence header.
Note that start codes (000001xx H) must be byte aligned by inserting 0 7 "0" bits before the start code.
This 32-bit field has a value of 000001B7 H and terminates a video sequence.
A sequence header should occur about every one-half second. The structure is shown in Figure 13.5. If not followed by a sequence extension, the bitstream conforms to MPEG-1.
This 32-bit string has a value of 000001B3 H and indicates the beginning of a sequence header.
This is the twelve least significant bits of the width (in samples) of the viewable portion of the Y component. The two most significant bits...
