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Add dual position parameter definition and parameter blocks #895

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452b57b
Add dual position parameter definition and parameter blocks
felicialim Jun 27, 2025
5b9f673
Merge branch 'AOMediaCodec:main' into dual_pos_params
felicialim Jun 30, 2025
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92 changes: 90 additions & 2 deletions index.bs
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Original file line number Diff line number Diff line change
Expand Up @@ -687,7 +687,7 @@ class AudioElementOBU() {
else if (param_definition_type == PARAMETER_DEFINITION_RECON_GAIN) {
ReconGainParamDefinition recon_gain_info;
}
else if (param_definition_type > 3) {
else if (param_definition_type > 4) {
leb128() param_definition_size;
unsigned int (8 x param_definition_size) param_definition_bytes;
}
Expand Down Expand Up @@ -776,18 +776,22 @@ NOTE: For a given [=audio_element_type=], a future version of the specification
<tr>
<td>3</td><td>PARAMETER_DEFINITION_SINGLE_POSITION</td><td>[=SinglePositionParamDefinition()=]</td>
</tr>
<tr>
<td>4</td><td>PARAMETER_DEFINITION_DUAL_POSITION</td><td>[=DualPositionParamDefinition()=]</td>
</tr>
</table>

- The following types SHALL NOT be present in an [=Audio Element OBU=]:
- PARAMETER_DEFINITION_MIX_GAIN
- PARAMETER_DEFINITION_SINGLE_POSITION
- PARAMETER_DEFINITION_DUAL_POSITION
- The type SHALL NOT be duplicated in one [=Audio Element OBU=].
- When [=codec_id=] = <code>fLaC</code> or <code>ipcm</code>, the type PARAMETER_DEFINITION_RECON_GAIN SHALL NOT be present.
- When [=num_layers=] > 1, the type PARAMETER_DEFINITION_RECON_GAIN SHALL be present.
- When the [=loudspeaker_layout=] = 15 or the [=loudspeaker_layout=] of the (non-)scalable channel audio (i.e., [=num_layers=] = 1) is less than or equal to 3.1.2ch (i.e., Mono, Stereo, or 3.1.2ch), the type PARAMETER_DEFINITION_DEMIXING SHALL NOT be present.
- When the highest [=loudspeaker_layout=] of the scalable channel audio (i.e., [=num_layers=] > 1) is greater than 3.1.2ch, both PARAMETER_DEFINITION_DEMIXING and PARAMETER_DEFINITION_RECON_GAIN types SHALL be present.
- When [=num_layers=] = 1 and [=loudspeaker_layout=] is greater than 3.1.2ch (i.e., 5.1.2ch, 5.1.4ch, 7.1.2ch, or 7.1.4ch), the type PARAMETER_DEFINITION_DEMIXING MAY be present.
- An OBU parser SHALL be able to parse [=audio_element_obu/param_definition_type=] = P (where P > 3) and [=param_definition_size=]. The OBU parser SHOULD ignore the bytes indicated by [=param_definition_size=] that it does not recognize.
- An OBU parser SHALL be able to parse [=audio_element_obu/param_definition_type=] = P (where P > 4) and [=param_definition_size=]. The OBU parser SHOULD ignore the bytes indicated by [=param_definition_size=] that it does not recognize.

<dfn noexport>demixing_info</dfn> is an instance of the [=DemixingParamDefinition()=] class, which provides the parameter definition for the demixing information, which is used to reconstruct a scalable channel audio representation. The corresponding parameter data to be provided in [=Parameter Block OBU=]s with the same [=parameter_block_obu/parameter_id=] is specified in the [=DemixingInfoParameterData()=] class.

Expand Down Expand Up @@ -1408,6 +1412,8 @@ class RenderingConfig() {
leb128() param_definition_type;
if (param_definition_type == PARAMETER_DEFINITION_SINGLE_POSITION) {
SinglePositionParamDefinition single_position;
} else if (param_definition_type == PARAMETER_DEFINITION_DUAL_POSITION) {
DualPositionParamDefinition dual_position;
}
else {
leb128() rendering_config_params_extension_size;
Expand Down Expand Up @@ -1439,13 +1445,16 @@ Parsers encountering a reserved value of [=headphones_rendering_mode=] SHALL ign

- The type SHALL NOT be duplicated in one [=RenderingConfig()=].
- The PARAMETER_DEFINITION_SINGLE_POSITION type SHALL be present only when the referenced [=Audio Element=] has [=audio_element_type=] = OBJECT_BASED and [=num_objects=] = 1.
- The PARAMETER_DEFINITION_DUAL_POSITION type SHALL be present only when the referenced [=Audio Element=] has [=audio_element_type=] = OBJECT_BASED and [=num_objects=] = 2.
- The following types SHALL NOT be present in [=RenderingConfig()=]:
- PARAMETER_DEFINITION_MIX_GAIN
- PARAMETER_DEFINITION_DEMIXING
- PARAMETER_DEFINITION_RECON_GAIN

<dfn noexport>single_position</dfn> is an instance of the [=SinglePositionParamDefinition()=] class. It provides the parameter definition for the position that is used when rendering an [=Audio Element=] with one object. The corresponding parameter data to be provided in [=Parameter Block OBU=]s with the same [=parameter_block_obu/parameter_id=] is specified in the [=SinglePositionParameterData()=] class.

<dfn noexport>dual_position</dfn> is an instance of the [=DualPositionParamDefinition()=] class. It provides the parameter definition for the position that is used when rendering an [=Audio Element=] with two objects. The corresponding parameter data to be provided in [=Parameter Block OBU=]s with the same [=parameter_block_obu/parameter_id=] is specified in the [=DualPositionParameterData()=] class.

<dfn noexport>rendering_config_params_extension_size</dfn> indicates the size in bytes of [=rendering_config_params_extension_bytes=].

<dfn noexport>rendering_config_params_extension_bytes</dfn> represents reserved bytes for future use. Parsers that don't understand these bytes SHOULD ignore them.
Expand Down Expand Up @@ -1485,6 +1494,40 @@ where 0 degrees is horizontally ahead and positive angles are going up, followin

<dfn noexport>default_distance</dfn> specifies the default distance, when there are no [=Parameter Block OBU=]s with the same [=parameter_block_obu/parameter_id=] provided. The value is expressed as a normalized distance from the origin in the range [0.0, 1.0], where 1.0 is on the surface of the unit sphere.

### Dual Position Parameter Definition Syntax and Semantics ### {#syntax-dual-position-parameter-definition}

The <dfn noexport>DualPositionParamDefinition()</dfn> class provides the parameter definition for two objects' positions.

This section specifies the syntax structures of the [=DualPositionParamDefinition()=] class.

<b>Syntax</b>

```
class DualPositionParamDefinition() extends ParamDefinition() {
signed int (9) default_first_azimuth;
signed int (8) default_first_elevation;
unsigned int (3) default_first_distance;

signed int (9) default_second_azimuth;
signed int (8) default_second_elevation;
unsigned int (3) default_second_distance;
}
```

<b>Semantics</b>

<dfn noexport>default_first_azimuth</dfn> is the same as [=default_azimuth=] in [=SinglePositionParamDefinition()=] except that this applies to the first object in the referenced [=Audio Substream=].

<dfn noexport>default_first_elevation</dfn> is the same as [=default_elevation=] in [=SinglePositionParamDefinition()=] except that this applies to the first object in the referenced [=Audio Substream=].

<dfn noexport>default_first_distance</dfn> is the same as [=default_distance=] in [=SinglePositionParamDefinition()=] except that this applies to the first object in the referenced [=Audio Substream=].

<dfn noexport>default_second_azimuth</dfn> is the same as [=default_azimuth=] in [=SinglePositionParamDefinition()=] except that this applies to the second object in the referenced [=Audio Substream=].

<dfn noexport>default_second_elevation</dfn> is the same as [=default_elevation=] in [=SinglePositionParamDefinition()=] except that this applies to the second object in the referenced [=Audio Substream=].

<dfn noexport>default_second_distance</dfn> is the same as [=default_distance=] in [=SinglePositionParamDefinition()=] except that this applies to the second object in the referenced [=Audio Substream=].


### Mix Gain Parameter Definition Syntax and Semantics ### {#syntax-mixgain-parameter-definition}

Expand Down Expand Up @@ -1714,6 +1757,9 @@ class ParameterBlockOBU() {
else if (param_definition_type == PARAMETER_DEFINITION_SINGLE_POSITION) {
SinglePositionParameterData single_position_parameter_data;
}
else if (param_definition_type == PARAMETER_DEFINITION_DUAL_POSITION) {
DualPositionParameterData dual_position_parameter_data;
}
else {
leb128() parameter_data_size;
unsigned int (8 x parameter_data_size) parameter_data_bytes;
Expand Down Expand Up @@ -1756,6 +1802,8 @@ The values of [=parameter_block_obu/duration=], [=parameter_block_obu/constant_s

<dfn noexport>single_position_parameter_data</dfn> is an instance of the [=SinglePositionParameterData()=] class, which provides the parameter values to apply in this parameter block.

<dfn noexport>dual_position_parameter_data</dfn> is an instance of the [=DualPositionParameterData()=] class, which provides the parameter values to apply in this parameter block.

<dfn noexport>parameter_data_size</dfn> indicates the size in bytes of [=parameter_data_bytes=].

<dfn noexport>parameter_data_bytes</dfn> represents reserved bytes for future use when new syntaxes are defined. Parsers that don't understand these bytes SHOULD ignore them.
Expand Down Expand Up @@ -1954,6 +2002,46 @@ where 0 degrees is horizontally ahead and positive angles are going up, followin
</table>


### Dual Position Parameter Data Syntax and Semantics ### {#syntax-dual-position-param}

The <dfn noexport>DualPositionParameterData()</dfn> class provides the position parameter data to be used when rendering an object-based [=Audio Element=] with two objects. This section specifies the syntax structure of the [=DualPositionParameterData()=] class.

<b>Syntax</b>

```
class DualPositionParameterData() {
leb128() dual_position_parameter_data_size;
leb128() animation_type;

AnimatedParameterData<signed int (9)> first_azimuth;
AnimatedParameterData<signed int (8)> first_elevation;
AnimatedParameterData<unsigned int (3)> first_distance;

AnimatedParameterData<signed int (9)> second_azimuth;
AnimatedParameterData<signed int (8)> second_elevation;
AnimatedParameterData<unsigned int (3)> second_distance;
}
```

<b>Semantics</b>

<dfn noexport>dual_position_parameter_data_size</dfn> indicates the size in bytes of [=DualPositionParameterData()=] immediately following this field. Parsers SHOULD ignore bytes past the [=DualPositionParameterData()=] syntax that they recognize.

<dfn noexport for="dual_position_param_data">animation_type</dfn> specifies the type of animation applied to the parameter values. Supported values are defined in the [=Animation Types=] table. When an unknown value of [=dual_position_param_data/animation_type=] is used, parsers SHOULD ignore the [=Parameter Block OBU=] that contains this [=dual_position_parameter_data=].

<dfn noexport>first_azimuth</dfn> is the same as [=azimuth=] in [=SinglePositionParameterData()=] except that this applies to the first object in the referenced [=Audio Substream=].

<dfn noexport>first_elevation</dfn> is the same as [=elevation=] in [=SinglePositionParameterData()=] except that this applies to the first object in the referenced [=Audio Substream=].

<dfn noexport>first_distance</dfn> is the same as [=distance=] in [=SinglePositionParameterData()=] except that this applies to the first object in the referenced [=Audio Substream=].

<dfn noexport>second_azimuth</dfn> is the same as [=azimuth=] in [=SinglePositionParameterData()=] except that this applies to the second object in the referenced [=Audio Substream=].

<dfn noexport>second_elevation</dfn> is the same as [=elevation=] in [=SinglePositionParameterData()=] except that this applies to the second object in the referenced [=Audio Substream=].

<dfn noexport>second_distance</dfn> is the same as [=distance=] in [=SinglePositionParameterData()=] except that this applies to the second object in the referenced [=Audio Substream=].


## Audio Frame OBU Syntax and Semantics ## {#obu-audioframe}

The <dfn noexport>Audio Frame OBU</dfn> provides the coded audio frame for an [=Audio Substream=]. This section specifies the payload format of the [=Audio Frame OBU=].
Expand Down