Processing of time-varying metadata for lossless resampling
Embodiments are directed to a method of representing spatial rendering metadata for processing in an object-based audio system that allows for lossless interpolation and/or re-sampling of the metadata. The method comprises time stamping the metadata to create metadata instances, and encoding an interpolation duration to with each metadata instance that specifies the time to reach a desired rendering state for the respective metadata instance. The re-sampling of metadata is useful for re-clocking metadata to an audio coder and for the editing audio content.
1. A method, performed by an audio signal processing device, for resampling a sequence of metadata instances representing time-varying rendering metadata in an object-based audio system, wherein each metadata instance:
specifies a desired rendering state;
is associated with a time stamp, the time stamp indicating a point in time to begin a transition from a current rendering state to the desired rendering state; and
includes one or more parameters indicative of the time stamp and an interpolation duration parameter indicating the required time to reach the desired rendering state;
the method comprising:
receiving or generating the sequence of metadata instances;
generating one or more additional metadata instances; and
inserting the one or more additional metadata instances between a first and a second metadata instance of the sequence of metadata instances to generate the resampled metadata sequence;
wherein the one or more additional metadata instances are substantially similar to the first metadata instance and/or the second metadata instance, with the exception of the interpolation duration parameter, which is different than the interpolation duration parameters of the first metadata instance and/or the second metadata instance; and
wherein the desired rendering state is determined by converting the metadata instance into coefficients specifying gain factors for playback of audio content through audio drivers in a playback system.
2. The method of claim 1 wherein the desired rendering state represents one of: a spatial rendering vector or rendering matrix.
3. The method of claim 1 wherein the metadata describes spatial rendering data of one or more audio objects.
4. The method of claim 3 wherein the metadata describes how an object should be rendered through the audio drivers in the playback system.
5. The method of claim 1 wherein the time stamp represents the start of the transition from the current rendering state to the desired rendering state.
6. The method of claim 5 wherein the time stamp is defined relative to a reference point in the audio content processed by the object-based audio system.
7. The method of claim 1 further comprising:
determining if the current state does not significantly deviate from the desired state; and
removing one or more metadata instances in between the current state and the desired state if the change does not significantly deviate.
8. The method of claim 1 further comprising converting each metadata instance into a set of values defining one of a spatial rendering vector or rendering matrix defining the desired rendering state.
9. The method of claim 1 wherein the metadata instances include metadata elements that define one or more object attributes selected from the group consisting of: object position, object size, and object zone exclusion.
10. An audio signal processing device for resampling a sequence of metadata instances representing time-varying rendering metadata in an object-based audio system, wherein each metadata instance:
specifies a desired rendering state;
is associated with a time stamp, the time stamp indicating a point in time to begin a transition from a current rendering state to the desired rendering state; and
includes one or more parameters indicative of the time stamp and an interpolation duration parameter indicating the required time to reach the desired rendering state;
and wherein the audio signal processing device:
receives or generates the sequence of metadata instances;
generates one or more additional metadata instances; and
inserts the one or more additional metadata instances between a first and a second metadata instance of the sequence of metadata instances to generate the resampled metadata sequence;
wherein the one or more additional metadata instances are substantially similar to the first metadata instance and/or the second metadata instance, with the exception of the interpolation duration parameter, which is different than the interpolation duration parameters of the first metadata instance and/or the second metadata instance; and
wherein the desired rendering state is determined by converting the metadata instance into coefficients specifying gain factors for playback of audio content through audio drivers in a playback system.
11. The audio signal processing device of claim 10 wherein the desired rendering state represents one of: a spatial rendering vector or rendering matrix, and wherein the metadata describes spatial rendering data of one or more audio objects.
12. The audio signal processing device of claim 10 wherein the playback system is selected from a group consisting of: digital media disc player, home theater system, soundbar, personal music device, and cinema sound system.
13. The audio signal processing device of claim 12 wherein the metadata describes how an object should be rendered through the playback system, and wherein the metadata include one or more object attributes selected from the group consisting of: object position, object size, and object zone exclusion.
14. The audio signal processing device of claim 10 , wherein the device further:
determines if a change between the current state does not significantly deviate from the desired state; and
removes one or more metadata instances in between the current state and the desired state if the change does not significantly deviate.
15. A method, performed by an audio signal processing device, for generating a sequence of rendering states, comprising:
receiving a sequence of metadata instances representing time-varying rendering metadata of an object-based audio system, wherein:
each metadata instance is associated with a time stamp, the time stamp indicating a point in time to begin a transition from a current rendering state to a desired rendering state;
each metadata instance includes one or more parameters indicative of the time stamp and an interpolation duration parameter indicating the required time to reach the desired rendering state; and
one or more consecutive metadata instances are substantially similar to a previous or subsequent metadata instance, with the exception of the interpolation duration parameter, which is different than the interpolation duration parameters of the previous or subsequent metadata instances;
converting each metadata instance into a respective desired rendering state comprising coefficients specifying gain factors for playback of audio content through audio drivers in a playback system; and
determining the sequence of rendering states by interpolating, for each metadata instance, from the current rendering state to the respective desired rendering state, in response to the interpolation duration parameter.
16. An audio signal processing device for generating a sequence of rendering states, wherein the audio signal processing device:
receives a sequence of metadata instances representing time-varying rendering metadata of an object-based audio system, wherein:
each metadata instance is associated with a time stamp, the time stamp indicating a point in time to begin a transition from a current rendering state to a desired rendering state;
each metadata instance includes one or more parameters indicative of the time stamp and an interpolation duration parameter indicating the required time to reach the desired rendering state; and
one or more consecutive metadata instances are substantially similar to a previous or subsequent metadata instance, with the exception of the interpolation duration parameter, which is different than the interpolation duration parameters of the previous or subsequent metadata instances;
converts each metadata instance into a respective desired rendering state comprising coefficients specifying gain factors for playback of audio content through audio drivers in a playback system; and
determines the sequence of rendering states by interpolating, for each metadata instance, from the current rendering state to the respective desired rendering state, in response to the interpolation duration parameter.