Abstract: In general, techniques are described for specifying audio rendering information in a bitstream. A device configured to generate the bitstream may perform various aspects of the techniques. The bitstream generation device may comprise one or more processors configured to specify audio rendering information that includes a signal value identifying an audio renderer used when generating the multi-channel audio content. A device configured to render multi-channel audio content from a bitstream may also perform various aspects of the techniques. The rendering device may comprise one or more processors configured to determine audio rendering information that includes a signal value identifying an audio renderer used when generating the multi-channel audio content, and render a plurality of speaker feeds based on the audio rendering information.

Abstract: Systems and techniques for rendering audio data are generally disclosed. An example device for rendering a higher order ambition (HOA) audio signal includes a memory configured to store the HOA audio signal, and one or more processors coupled to the memory. The one or more processors are configured to perform a loudness compensation process as part of generating an effect matrix. The one or more processors are further configured to render the HOA audio signal based on the effect matrix.

Abstract: In general, techniques are described for specifying spherical harmonic coefficients in a bitstream. A device comprising one or more processors may perform the techniques. The processors may be configured to identify, from the bitstream, a plurality of hierarchical elements describing a sound field that are included in the bitstream. The processors may further be configured to parse the bitstream to determine the identified plurality of hierarchical elements.

Abstract: This disclosure describes techniques for coding of higher-order ambisonics audio data comprising at least one higher-order ambisonic (HOA) coefficient corresponding to a spherical harmonic basis function having an order greater than one. This disclosure describes techniques for adjusting HOA soundfields to potentially improve spatial alignment of the acoustic elements to the visual component in a mixed audio/video reproduction scenario. In one example, a device for rendering an HOA audio signal includes one or more processors configured to render the HOA audio signal over one or more speakers based on one or more field of view (FOV) parameters of a reference screen and one or more FOV parameters of a viewing window.

Abstract: In general, techniques are described for mapping virtual speakers to physical speakers, having first adjusted the position of one of the virtual speakers based on a relative position of the one of the virtual speakers to one of the physical speakers. A device comprising one or more processors may perform the techniques. The one or more processors may be configured to determine a difference in position between one of a plurality of physical speakers and one of a plurality of virtual speakers arranged in a geometry, and adjust a position of the one of the plurality of virtual speakers within the geometry based on the determined difference in position and prior to mapping the plurality of virtual speakers to the plurality of physical speakers.

Abstract: In general, techniques are described for obtaining one or more first vectors describing distinct components of a soundfield and one or more second vectors describing background components of the soundfield, both the one or more first vectors and the one or more second vectors generated at least by performing a transformation with respect to a plurality of spherical harmonic coefficients.

Abstract: In general, techniques are described for obtaining audio rendering information in a bitstream. A device configured to render higher order ambisonic coefficients comprising a processor and a memory may perform the techniques. The processor may be configured to obtain sign symmetry information indicative of sign symmetry of a matrix used to render the higher order ambisonic coefficients to generate a plurality of speaker feeds. The memory may be configured to store the sparseness information.

Abstract: In general, techniques are described for obtaining audio rendering information in a bitstream. A device configured to render higher order ambisonic coefficients comprising a processor and a memory may perform the techniques. The processor may be configured to obtain sparseness information indicative of a sparseness of a matrix used to render the higher order ambisonic coefficients to a plurality of speaker feeds. The memory may be configured to store the sparseness information.

Abstract: In general, techniques are described for compression and decoding of audio data are generally disclosed. An example device for compressing audio data includes one or more processors configured to apply a decorrelation transform to ambient ambisonic coefficients to obtain a decorrelated representation of the ambient ambisonic coefficients, the ambient HOA coefficients having been extracted from a plurality of higher order ambisonic coefficients and representative of a background component of a soundfield described by the plurality of higher order ambisonic coefficients, wherein at least one of the plurality of higher order ambisonic coefficients is associated with a spherical basis function having an order greater than one.

Abstract: In general, techniques are described for determining renderers used for rendering spherical harmonic coefficients to generate one or more loudspeaker signals. A device comprising one or more processors may perform the techniques. The one or more processors may be configured to determine a local speaker geometry of one or more speakers used for playback of spherical harmonic coefficients representative of a sound field, and configure the device to operate based on the local speaker geometry.

Abstract: In general, techniques are described for audio editing of higher-order ambisonic audio data. A device comprising a memory and one or more processors may be configured to perform the techniques. The memory may be configured to store a higher order ambisonic (HOA) representation of the audio object. The one or more processors may be configured to add a source tail to the HOA representation of the audio object by storing one or more spherical harmonic (SH) basis functions associated with the audio object to a buffer.

Abstract: In general, techniques are described for obtaining audio rendering information in a bitstream. A device configured to render higher order ambisonic coefficients comprising a processor and a memory may perform the techniques. The processor may be configured to obtain sparseness information indicative of a sparseness of a matrix used to render the higher order ambisonic coefficients to a plurality of speaker feeds. The memory may be configured to store the sparseness information.

Abstract: In general, techniques are described for transforming spherical harmonic coefficients. A device comprising one or more processors may perform the techniques. The processors may be configured to parse the bitstream to determine transformation information describing how the sound field was transformed to reduce a number of the plurality of hierarchical elements that provide information relevant in describing the sound field. The processors may further be configured to, when reproducing the sound field based on those of the plurality of hierarchical elements that provide information relevant in describing the sound field, transform the sound field based on the transformation information to reverse the transformation performed to reduce the number of the plurality of hierarchical elements.

Abstract: A device comprising one or more processors is configured to determine a plurality of segments for each of a plurality of binaural room impulse response filters, wherein each of the plurality of binaural room impulse response filters comprises a residual room response segment and at least one direction-dependent segment for which a filter response depends on a location within a sound field; transform each of at least one direction-dependent segment of the plurality of binaural room impulse response filters to a domain corresponding to a domain of a plurality of hierarchical elements to generate a plurality of transformed binaural room impulse response filters, wherein the plurality of hierarchical elements describe a sound field; and perform a fast convolution of the plurality of transformed binaural room impulse response filters and the plurality of hierarchical elements to render the sound field.

Abstract: Systems and techniques for rendering audio data are generally disclosed. An example device for rendering a higher order ambition (HOA) audio signal includes a memory configured to store the HOA audio signal, and one or more processors coupled to the memory. The one or more processors are configured to perform a loudness compensation process as part of generating an effect matrix. The one or more processors are further configured to render the HOA audio signal based on the effect matrix.

Abstract: In general, techniques are described for obtaining audio rendering information in a bitstream. A device configured to render higher order ambisonic coefficients comprising a processor and a memory may perform the techniques. The processor may be configured to obtain sparseness information indicative of a sparseness of a matrix used to render the higher order ambisonic coefficients to a plurality of speaker feeds. The memory may be configured to store the sparseness information.

Abstract: In general, techniques are described for editing of higher-order ambisonic audio data. A device comprising a memory and one or more processors may be configured to perform the techniques. The memory may be configured to store spherical harmonic (SH) basis functions. The one or more processors may be configured to manipulate the SH basis functions associated with higher order ambisonics coefficients to alter a direction of an audio object represented by the higher order ambisonics coefficients.

Abstract: In general, techniques are described for obtaining an indication of whether spherical harmonic coefficients are representative of a synthetic audio object. In accordance with the techniques, a device comprising one or more processors may be configured to obtain an indication of whether spherical harmonic coefficients representative of a sound field are generated from a synthetic audio object.

Abstract: In general, techniques are described for performing a positional analysis to code audio data. Typically, this audio data comprises a hierarchical representation of a soundfield and may include, as one example, spherical harmonic coefficients (which may also be referred to as higher-order ambisonic coefficients). An audio compression device that includes one or more processors may perform the techniques. The processors may be configured to allocate bits to one or more portions of the audio data, at least in part by performing positional analysis on the audio data.

Abstract: In general, techniques are described for coding of spherical harmonic coefficients representative of a three dimensional soundfield. A device comprising a memory and one or more processors may be configured to perform the techniques. The memory may be configured to store a plurality of spherical harmonic coefficients. The one or more processors may be configured to perform an energy analysis with respect to the plurality of spherical harmonic coefficients to determine a reduced version of the plurality of spherical harmonic coefficients.