Audio sample rate for a sample entry

Overview

Containing profile atom: Track (sound), movie
part-ID: 0x20202020 (universal feature)
feature-code: 'ausr'
feature-value: Unsigned int(32) holding the audio sample rate in units per second (for example, 44100 for 44.1 kHz)

Feature Values

This feature value is an unsigned 32-bit integer holding the audio sample rate in units per seconds (cycles per second). The value should be rounded up to the nearest integer if it has a fractional portion.

Examples: 24 kHz = 24000, 44.1 kHz = 44100.

Writer Responsibilities

A writer of the Audio Sample Rate feature should record the integer portion (rounded up if there is a fractional portion) of the audio sample rate found in a sound track’s SoundDescription structure.

If multiple audio sample rates are used in the movie, then either all must recorded in the profile atom, or none must be recorded.

Feature Value Algorithm

This is the integer portion of the sample rate from a QuickTime audio sample description (rounded up if there is a fractional portion). If the sample rate is greater than 64 kHz, the integer portion can be recorded here.

If a sample rate has a fractional portion, the writer should round up to the nearest integer. So, the 22254.54545 value that may occur in QuickTime audio as a Fixed value represented as 0x56EE8BA3 can be recorded as 22255.

Reader Responsibilities

A reader of this feature code should compare the recorded value with its own audio sample rate limits. If the reader only supports discrete values (such as 44100), it can perform equality comparisons (=). If the reader supports ranges of audio sample rates (such as all rates less than or equal to 32000), the reader can perform relative comparisons (<, <=, >, or >=).