# audioPackFormat (Matrix)

The audioPackFormat with typeDefinition 'Matrix' needs extra sub-elements to allow the definition of encoding (e.g. Left/Right to Mid/Side), decoding (e.g. Mid/Side to Left/Right) and direct (e.g. Lo/Ro) matrices.

The matrix can either be an encoding, a decoding or a direct matrix. An encoding matrix converts an input pack of any type (though “DirectSpeakers” would be the most likely to be used) into a matrix-encoded pack. A decoding matrix takes matrix-encoded pack and converts into a channel-based output pack. Related encoding and decoding matrices can be cross-referenced.

For example, Stereo to Mid/Side would be an encoding matrix, and Mid/Side to Stereo would be a decoding matrix.

The diagram below how encoder and decoder matrix audioPackFormats relate to each other, as well in the input and output audioPackFormats and audioChannelFormats.

The diagram below shows how a direct matrix audioPackFormat relates to input and output audioPackFormats and audioChannelFormats.

## Attributes

There are no additional attributes defined for the audioPackFormat with typeDefinition 'Matrix'. 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 'Matrix'.

Even though it is defined as a common sub-element, the absoluteDistance sub-element is unlikely to be used in the 'Matrix' mode.

Sub-element Description Example Quantity
audioChannelFormatIDRef Reference to an audioChannelFormat AC_00021001 0...*
audioPackFormatIDRef Reference to an audioPackFormat AP_00021002 0...*
absoluteDistance Absolute distance in metres 4.5 0 or 1
encodePackFormatIDRef Reference to an encoding matrix audioPackFormat from a decoding matrix. AP_00020001 0…*
decodePackFormatIDRef Reference to a decoding matrix audioPackFormat from an encoding matrix. AP_00020101 0 …*
inputPackFormatIDRef Reference to a channel-based (DirectSpeakers) input audioPackFormat. AP_00010002 0 or 1
outputPackFormatIDRef Reference to a channel-based (DirectSpeakers) matrix decoded audioPackFormat. AP_00010002 0 or 1

The encoding matrix contains an inputPackFormatIDRef, which references a channel-based input pack. It can also contain a list of decodePackFormatIDRefs, which are references to corresponding decoding matrices.

The decoding matrix contains an outputPackFormatIDRef, which reference a channel-based output pack. It can also contain a list of encodePackFormatIDRefs, which are references to corresponding encoding matrices.

The direct matrix contains an inputPackFormatIDRef, which references a channel-based input pack and an outputPackFormatIDRef, which reference a channel-based output pack.

## Example

<audioPackFormat audioPackFormatID="AP_00021001"
audioPackFormatName="PackMat1_Encode"
typeLabel="0002" typeDefinition="Matrix">
<audioChannelFormatIDRef>AC_00021001</audioChannelFormatIDRef>
<audioChannelFormatIDRef>AC_00021002</audioChannelFormatIDRef>
<decodePackFormatIDRef>AP_00021101</decodePackFormatIDRef>
<inputPackFormatIDRef>AP_00010002</inputPackFormatIDRef>
</audioPackFormat>