Chapter 5. H.264 syntax


An 'H.264 video' is a video sequence that is represented in a particular format, the H.264/AVC syntax. This syntax is defined in the H.264 industry standard and specifies the exact structure of an H.264-compliant video sequence, in terms of syntax elements, parameters describing different aspects of the coded sequence, and the way in which each element is represented as a binary code. The syntax is hierarchical, from the highest level, the video sequence level, down through individual coded frames or fields (access units) and subsets of access units (slices) to macroblocks and blocks. Control parameters are stored as separate syntax sections such as Parameter Sets or as part of sections such as the macroblock layer. This chapter examines the H.264/AVC syntax in detail, beginning with an overview of frame and picture structures and handling, followed by each of the main layers of the syntax hierarchy.

A note about syntax examples

The various syntax sections in the H.264/AVC standard are illustrated later in the chapter with extracts from coded video sequences. These were generated using the Joint Model software video codec [[32]] using the 'Trace' mode which is described further in Chapter 9. Each syntax example is presented in the following way, Table 5.1:

Table 5.1. Syntax examples: format


Binary code






Baseline Profile

↑ The name of the syntax parameter, listed in the H.264/AVC standard

↑ The binary code

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