Methods, apparatus and systems for encoding and decoding of directional sound sources
Some disclosed methods involve encoding or decoding directional audio data. Some encoding methods may involve receiving a mono audio signal corresponding to an audio object and a representation of a radiation pattern corresponding to the audio object. The radiation pattern may include sound levels corresponding to plurality of sample times, a plurality of frequency bands and a plurality of directions. The methods may involve encoding the mono audio signal and encoding the source radiation pattern to determine radiation pattern metadata. Encoding the radiation pattern may involve determining a spherical harmonic transform of the representation of the radiation pattern and compressing the spherical harmonic transform to obtain encoded radiation pattern metadata.
1. A method for decoding audio data, comprising:
receiving an encoded core audio signal, encoded radiation pattern metadata and encoded audio object metadata, wherein the audio object metadata includes Six Degrees of Freedom (6DoF) source orientation information;
decoding the encoded core audio signal to determine a core audio signal;
decoding the encoded radiation pattern metadata to determine a decoded radiation pattern;
rendering the core audio signal based on the audio object metadata and the decoded radiation pattern.
2. The method of claim 1 , wherein the core audio signal comprises a plurality of directional objects based on a cluster of objects, and wherein the decoded radiation pattern is representative of a centroid that reflects an average value for each frequency band.
3. The method of claim 1 , wherein the encoded radiation pattern metadata corresponds with a time—and frequency-varying set of spherical harmonic coefficients.
4. The method of claim 1 , wherein the encoded radiation pattern metadata comprises audio object type metadata.
5. The method of claim 4 , wherein the audio object type metadata indicates parametric directivity pattern data and wherein the parametric directivity pattern data includes one or more functions selected from a list of functions that consists of a cosine function, a sine function or a cardioidal function.
6. The method of claim 4 , wherein the audio object type metadata indicates dynamic directivity pattern data and wherein the dynamic directivity pattern data corresponds with a time—and frequency-varying set of spherical harmonic coefficients.
7. The method of claim 6 , further comprising receiving the dynamic directivity pattern data prior to receiving the encoded core audio signal.
8. The method of claim 1 , wherein the rendering is based on applying subband gains, based at least in part on the decoded radiation pattern, to the decoded core audio signal.
9. The method of claim 4 wherein the audio object type metadata indicates database directivity pattern data and wherein decoding the encoded radiation pattern metadata to determine the decoded radiation pattern comprises querying a directivity data structure that includes audio object types and corresponding directivity pattern data.
10. A non-transitory computer-readable medium having stored thereon instructions, that when executed by one or more processors, cause one or more processors to perform the method of 1 .
11. An audio decoding apparatus, comprising:
an interface system; and
a control system configured for:
receiving, via the interface system, audio data corresponding to at least one audio object, the audio data including a monophonic audio signal, audio object position metadata, and a rendering parameter, wherein the audio object position metadata includes
Six Degrees of Freedom (6DoF) source orientation information; determining whether the rendering parameter indicates a positional mode or a directivity mode; and, upon determining that the rendering parameter indicates a directivity mode, rendering the audio data for reproduction via at least one loudspeaker according to a directivity pattern indicated by at least one of the audio object position metadata.