audioChannelFormat
Description
An audioChannelFormat represents a single sequence of audio samples on which some action may be performed, such as movement of an object, which is rendered in a scene. It contains one or more audioBlockFormats, which sub-divide it in the time domain. The typeDefinition/typeLabel is used to define the type of channel.
The types of audioChannelFormats are:
Common Attributes
| Attribute | Description | Example | Required |
|---|---|---|---|
| audioChannelFormatName | Name of the channel | FrontLeft | Yes |
| audioChannelFormatID | ID of the channel. The yyyy digits of AC_yyyyxxxx_represent the type of audio contained in the channel. The xxxx digits should match the audioStreamFormat xxxx digits. | AC_00010001 | Yes |
| typeLabel | Descriptor of the type of channel | 0001 | Optional |
| typeDefinition | Description of the type of channel | DirectSpeakers | Optional |
* At least one of typeLabel or typeDefinition is required.
The typeDefinition of the audioChannelFormat specifies the type of audio it is describing, and also determines which parameters are used within its audioBlockFormat children.
Common Sub-elements
| Sub-element | Description | Attributes | Quantity |
|---|---|---|---|
| audioBlockFormat | Time division of channel containing dynamic metadata | 1...* | |
| frequency | Sets a high or low cut-off frequency for the audio in Hz | typeDefinition = “lowPass" or “highPass" | 0...2 |
audioBlockFormat
An audioBlockFormat represents a single sequence of audioChannelFormat samples with fixed parameters, including position, within a specified time interval.
Attributes
| Attribute | Description | Example | Required | Default |
|---|---|---|---|---|
| audioBlockFormatID | ID for block | AB_00010001_00000001 | Yes | |
| rtime | Start time of block (relative to the start time of the parent audioObject) | 00:00:00.00000 | Optional | 00:00:00.00000 |
| duration | Duration time of block. | 00:00:10.00000 | Optional | unbounded duration |
The last 8 hexadecimal digits in the audioBlockFormatID contain the index for the block within the channel, starting at 00000001 for the first block.
If rtime is not used then the block starts at 00:00:00.00000. If duration is not used then the block lasts for the whole duration of the channel.
If there is only one audioBlockFormat within an audioChannelFormat it is assumed to be a ‘static’ object that lasts the duration of the channel, therefore rtime and duration should be omitted. When there is more than one audioBlockFormat within an audioChannelFormat it is assumed to be a ‘dynamic’ object, therefore both rtime and duration should be used.
Time Format
The time is shown in the format ‘hh:mm:ss.zzzzz’ which indicate hours, minutes, seconds and fractional seconds.
Sub-elements
The sub-elements within audioBlockFormat depend upon the typeDefinition/typeLabel of the audioChannelFormat.