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[str]

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.

If specified, author defaultValue as the attribute’s default, sparsely (when it makes sense to do so) if writeSparsely is true - the default for writeSparsely is false .

Parameters
  • defaultValue (VtValue) –

  • writeSparsely (bool) –

CreateEndTimeAttr(defaultValue, writeSparsely) Attribute

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

If specified, author defaultValue as the attribute’s default, sparsely (when it makes sense to do so) if writeSparsely is true - the default for writeSparsely is false .

Parameters
  • defaultValue (VtValue) –

  • writeSparsely (bool) –

CreateFilePathAttr(defaultValue, writeSparsely) Attribute

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

If specified, author defaultValue as the attribute’s default, sparsely (when it makes sense to do so) if writeSparsely is true - the default for writeSparsely is false .

Parameters
  • defaultValue (VtValue) –

  • writeSparsely (bool) –

CreateGainAttr(defaultValue, writeSparsely) Attribute

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

If specified, author defaultValue as the attribute’s default, sparsely (when it makes sense to do so) if writeSparsely is true - the default for writeSparsely is false .

Parameters
  • defaultValue (VtValue) –

  • writeSparsely (bool) –

CreateMediaOffsetAttr(defaultValue, writeSparsely) Attribute

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

If specified, author defaultValue as the attribute’s default, sparsely (when it makes sense to do so) if writeSparsely is true - the default for writeSparsely is false .

Parameters
  • defaultValue (VtValue) –

  • writeSparsely (bool) –

CreatePlaybackModeAttr(defaultValue, writeSparsely) Attribute

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

If specified, author defaultValue as the attribute’s default, sparsely (when it makes sense to do so) if writeSparsely is true - the default for writeSparsely is false .

Parameters
  • defaultValue (VtValue) –

  • writeSparsely (bool) –

CreateStartTimeAttr(defaultValue, writeSparsely) Attribute

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

If specified, author defaultValue as the attribute’s default, sparsely (when it makes sense to do so) if writeSparsely is true - the default for writeSparsely is false .

Parameters
  • defaultValue (VtValue) –

  • writeSparsely (bool) –

static Define()

classmethod Define(stage, path) -> SpatialAudio

Attempt to ensure a UsdPrim adhering to this schema at path is defined (according to UsdPrim::IsDefined() ) on this stage.

If a prim adhering to this schema at path is already defined on this stage, return that prim. Otherwise author an SdfPrimSpec with specifier == SdfSpecifierDef and this schema’s prim type name for the prim at path at the current EditTarget. Author SdfPrimSpec s with specifier == SdfSpecifierDef and empty typeName at the current EditTarget for any nonexistent, or existing but not Defined ancestors.

The given path must be an absolute prim path that does not contain any variant selections.

If it is impossible to author any of the necessary PrimSpecs, (for example, in case path cannot map to the current UsdEditTarget ‘s namespace) issue an error and return an invalid UsdPrim.

Note that this method may return a defined prim whose typeName does not specify this schema class, in case a stronger typeName opinion overrides the opinion at the current EditTarget.

Parameters
static Get()

classmethod Get(stage, path) -> SpatialAudio

Return a UsdMediaSpatialAudio holding the prim adhering to this schema at path on stage .

If no prim exists at path on stage , or if the prim at that path does not adhere to this schema, return an invalid schema object. This is shorthand for the following:

UsdMediaSpatialAudio(stage->GetPrimAtPath(path));
Parameters
GetAuralModeAttr() Attribute

Determines how audio should be played.

Valid values are:

  • spatial: Play the audio in 3D space if the device can support spatial audio. if not, fall back to mono.

  • nonSpatial: Play the audio without regard to the SpatialAudio prim’s position. If the audio media contains any form of stereo or other multi-channel sound, it is left to the application to determine whether the listener’s position should be taken into account. We expect nonSpatial to be the choice for ambient sounds and music sound- tracks.

Declaration

uniform token auralMode ="spatial"

C++ Type

TfToken

Usd Type

SdfValueTypeNames->Token

Variability

SdfVariabilityUniform

Allowed Values

spatial, nonSpatial

GetEndTimeAttr() Attribute

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.

This only applies if playbackMode is set to onceFromStartToEnd or loopFromStartToEnd, otherwise the endTimeCode of the stage is used instead of endTime. If endTime is less than startTime, it is expected that the audio will instead be played from endTime to startTime. Note that endTime is expressed as a timecode so that the stage can properly apply layer offsets when resolving its value. See Timecode Attributes and Time Scaling for more details and caveats.

Declaration

uniform timecode endTime = 0

C++ Type

SdfTimeCode

Usd Type

SdfValueTypeNames->TimeCode

Variability

SdfVariabilityUniform

GetFilePathAttr() Attribute

Path to the audio file.

In general, the formats allowed for audio files is no more constrained by USD than is image-type. As with images, however, usdz has stricter requirements based on DMA and format support in browsers and consumer devices. The allowed audio filetypes for usdz are M4A, MP3, WAV (in order of preference).

Usdz Specification

Declaration

uniform asset filePath = @@

C++ Type

SdfAssetPath

Usd Type

SdfValueTypeNames->Asset

Variability

SdfVariabilityUniform

GetGainAttr() Attribute

Multiplier on the incoming audio signal.

A value of 0”mutes”the signal. Negative values will be clamped to 0.

Declaration

double gain = 1

C++ Type

double

Usd Type

SdfValueTypeNames->Double

GetMediaOffsetAttr() Attribute

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.

If the prim’s playbackMode is a looping mode, mediaOffset is applied only to the first run-through of the audio clip; the second and all other loops begin from the start of the audio clip.

Declaration

uniform double mediaOffset = 0

C++ Type

double

Usd Type

SdfValueTypeNames->Double

Variability

SdfVariabilityUniform

GetPlaybackModeAttr() Attribute

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.

Valid values are:

  • onceFromStart: Play the audio once, starting at startTime, continuing until the audio completes.

  • onceFromStartToEnd: Play the audio once beginning at startTime, continuing until endTime or until the audio completes, whichever comes first.

  • loopFromStart: Start playing the audio at startTime and continue looping through to the stage’s authored endTimeCode.

  • loopFromStartToEnd: Start playing the audio at startTime and continue looping through, stopping the audio at endTime.

  • loopFromStage: Start playing the audio at the stage’s authored startTimeCode and continue looping through to the stage’s authored endTimeCode. This can be useful for ambient sounds that should always be active.

Declaration

uniform token playbackMode ="onceFromStart"

C++ Type

TfToken

Usd Type

SdfValueTypeNames->Token

Variability

SdfVariabilityUniform

Allowed Values

onceFromStart, onceFromStartToEnd, loopFromStart, loopFromStartToEnd, loopFromStage

static GetSchemaAttributeNames()

classmethod GetSchemaAttributeNames(includeInherited) -> list[str]

Return a vector of names of all pre-declared attributes for this schema class and all its ancestor classes.

Does not include attributes that may be authored by custom/extended methods of the schemas involved.

Parameters

includeInherited (bool) –

GetStartTimeAttr() Attribute

Expressed in the timeCodesPerSecond of the containing stage, startTime specifies when the audio stream will start playing during animation playback.

This value is ignored when playbackMode is set to loopFromStage as, in this mode, the audio will always start at the stage’s authored startTimeCode. Note that startTime is expressed as a timecode so that the stage can properly apply layer offsets when resolving its value. See Timecode Attributes and Time Scaling for more details and caveats.

Declaration

uniform timecode startTime = 0

C++ Type

SdfTimeCode

Usd Type

SdfValueTypeNames->TimeCode

Variability

SdfVariabilityUniform

class pxr.UsdMedia.Tokens

Attributes:

auralMode

endTime

filePath

gain

loopFromStage

loopFromStart

loopFromStartToEnd

mediaOffset

nonSpatial

onceFromStart

onceFromStartToEnd

playbackMode

spatial

startTime

auralMode = 'auralMode'
endTime = 'endTime'
filePath = 'filePath'
gain = 'gain'
loopFromStage = 'loopFromStage'
loopFromStart = 'loopFromStart'
loopFromStartToEnd = 'loopFromStartToEnd'
mediaOffset = 'mediaOffset'
nonSpatial = 'nonSpatial'
onceFromStart = 'onceFromStart'
onceFromStartToEnd = 'onceFromStartToEnd'
playbackMode = 'playbackMode'
spatial = 'spatial'
startTime = 'startTime'