UsdMedia module

Summary: The UsdMedia module provides a representation for including other media, such as audio, in the context of a stage. UsdMedia currently contains one media type, UsdMediaSpatialAudio, which allows the playback of audio files both spatially and non-spatially.

Classes:

`SpatialAudio`	The SpatialAudio primitive defines basic properties for encoding playback of an audio file or stream within a USD Stage.
`Tokens`

class pxr.UsdMedia.SpatialAudio

The SpatialAudio primitive defines basic properties for encoding playback of an audio file or stream within a USD Stage. The SpatialAudio schema derives from UsdGeomXformable since it can support full spatial audio while also supporting non-spatial mono and stereo sounds. One or more SpatialAudio prims can be placed anywhere in the namespace, though it is advantageous to place truly spatial audio prims under/inside the models from which the sound emanates, so that the audio prim need only be transformed relative to the model, rather than copying its animation.

Timecode Attributes and Time Scaling

startTime and endTime are timecode valued attributes which gives them the special behavior that layer offsets affecting the layer in which one of these values is authored are applied to the attribute’s value itself during value resolution. This allows audio playback to be kept in sync with time sampled animation as the animation is affected by layer offsets in the composition. But this behavior brings with it some interesting edge cases and caveats when it comes to layer offsets that include scale.

Although authored layer offsets may have a time scale which can scale the duration between an authored startTime and endTime, we make no attempt to infer any playback dilation of the actual audio media itself. Given that startTime and endTime can be independently authored in different layers with differing time scales, it is not possible, in general, to define an”original timeframe”from which we can compute a dilation to composed stage-time. Even if we could compute a composed dilation this way, it would still be impossible to flatten a stage or layer stack into a single layer and still retain the composed audio dilation using this schema.

Although we do not expect it to be common, it is possible to apply a negative time scale to USD layers, which mostly has the effect of reversing animation in the affected composition. If a negative scale is applied to a composition that contains authored startTime and endTime, it will reverse their relative ordering in time. Therefore, we stipulate when playbackMode is”onceFromStartToEnd”or”loopFromStartToEnd”, if endTime is less than startTime, then begin playback at endTime, and continue until startTime. When startTime and endTime are inverted, we do not, however, stipulate that playback of the audio media itself be inverted, since doing so”successfully”would require perfect knowledge of when, within the audio clip, relevant audio ends (so that we know how to offset the reversed audio to align it so that we reach the”beginning”at startTime), and sounds played in reverse are not likely to produce desirable results.

For any described attribute Fallback Value or Allowed Values below that are text/tokens, the actual token is published and defined in UsdMediaTokens. So to set an attribute to the value”rightHanded”, use UsdMediaTokens->rightHanded as the value.

Methods:

`CreateAuralModeAttr`(defaultValue, writeSparsely)	See GetAuralModeAttr() , and also Create vs Get Property Methods for when to use Get vs Create.
`CreateEndTimeAttr`(defaultValue, writeSparsely)	See GetEndTimeAttr() , and also Create vs Get Property Methods for when to use Get vs Create.
`CreateFilePathAttr`(defaultValue, writeSparsely)	See GetFilePathAttr() , and also Create vs Get Property Methods for when to use Get vs Create.
`CreateGainAttr`(defaultValue, writeSparsely)	See GetGainAttr() , and also Create vs Get Property Methods for when to use Get vs Create.
`CreateMediaOffsetAttr`(defaultValue, ...)	See GetMediaOffsetAttr() , and also Create vs Get Property Methods for when to use Get vs Create.
`CreatePlaybackModeAttr`(defaultValue, ...)	See GetPlaybackModeAttr() , and also Create vs Get Property Methods for when to use Get vs Create.
`CreateStartTimeAttr`(defaultValue, writeSparsely)	See GetStartTimeAttr() , and also Create vs Get Property Methods for when to use Get vs Create.
`Define`	classmethod Define(stage, path) -> SpatialAudio
`Get`	classmethod Get(stage, path) -> SpatialAudio
`GetAuralModeAttr`()	Determines how audio should be played.
`GetEndTimeAttr`()	Expressed in the timeCodesPerSecond of the containing stage, endTime specifies when the audio stream will cease playing during animation playback if the length of the referenced audio clip is longer than desired.
`GetFilePathAttr`()	Path to the audio file.
`GetGainAttr`()	Multiplier on the incoming audio signal.
`GetMediaOffsetAttr`()	Expressed in seconds, mediaOffset specifies the offset from the referenced audio file's beginning at which we should begin playback when stage playback reaches the time that prim's audio should start.
`GetPlaybackModeAttr`()	Along with startTime and endTime, determines when the audio playback should start and stop during the stage's animation playback and whether the audio should loop during its duration.
`GetSchemaAttributeNames`	classmethod GetSchemaAttributeNames(includeInherited) -> list[TfToken]
`GetStartTimeAttr`()	Expressed in the timeCodesPerSecond of the containing stage, startTime specifies when the audio stream will start playing during animation playback.

CreateAuralModeAttr(defaultValue, writeSparsely) → Attribute

See GetAuralModeAttr() , and also Create vs Get Property Methods for when to use Get vs Create.