Audio variable bit rate indication

Overview

Containing profile atom: Track (sound), movie
part-ID: 0x20202020 (universal feature)
feature-code: 'avbr'
feature-value: Unsigned int(32) holding the value 0 if the audio is constant bit rate or 1 if the audio is variable bit rate

Feature Values

The feature value holds one of the following two values: 0 if the audio is constant bit rate, or 1 if the audio is variable bit rate.

Writer Responsibilities

A writer of the Audio Variable Bit Rate Indication feature should determine if the audio frames are constant or variable bit rate in nature and record either 0 or 1, respectively.

Feature Value Algorithm

Consult the audio sample descriptions. If the compressionID field in the sample descriptions is 0 or -1, then the audio is constant bit rate. If the field is -2, then the same algorithm as for video applies: if all the samples have both constant duration and constant size, then the audio is constant bit rate; otherwise it is variable.

Reader Responsibilities

A reader of this feature code should only expect the values 0 or 1.