# audioPackFormat (HOA)

The audioPackFormat with typeDefinition 'HOA' is used for scene-based audio (such as Higher Order Ambisonics). Many audioPackFormat definitions with the 'HOA' type are already defined in the Common Definitions, so they do not need to be defined explicitly when generating ADM metadata.

It is common that a pack of HOA components/signals will share the same normalization, NFC compensation and/or screen-relation. However, when the parameters are specified within an audioBlockFormat, these values overwrite those given in the audioPackFormat.

## Attributes

There are no additional attributes defined for the audioPackFormat with typeDefinition 'HOA'. See Common Attributes for the list of common ones.

## Sub-elements

In addition to the common sub-elements the following sub-elements are defined for the audioPackFormat with typeDefinition 'HOA'.

Sub-element Description Example Quantity Default
audioChannelFormatIDRef Reference to an audioChannelFormat AC_00040001 0...* -
audioPackFormatIDRef Reference to an audioPackFormat AP_00040002 0...* -
absoluteDistance Absolute distance in metres 4.5 0 or 1 -
normalization Indicates the normalization scheme of the HOA content (N3D, SN3D, FuMa). N3D 0 or 1 SN3D
nfcRefDist Indicates the reference distance (in metres) of the loudspeaker setup for near-field compensation (NFC). If no nfcRefDist is defined or the value is 0, NFC is not necessary. 2 0 or 1 0
screenRef Indicates whether the content is screen-related (flag is equal to 1) or not (flag is equal to 0) 0 0 or 1 0

## Example

<audioPackFormat audioPackFormatID="AP_00040001"
audioPackFormatName="3D_order1_SN3D_ACN"
typeLabel="0004" typeDefinition="HOA">
<audioChannelFormatIDRef>AC_00040001</audioChannelFormatIDRef>
<audioChannelFormatIDRef>AC_00040002</audioChannelFormatIDRef>
<audioChannelFormatIDRef>AC_00040003</audioChannelFormatIDRef>
<audioChannelFormatIDRef>AC_00040004</audioChannelFormatIDRef>
</audioPackFormat>