Abstract: In general, techniques are described for signaling channels for scalable coding of higher order ambisonic audio data. A device comprising a memory and a processor may be configured to perform the techniques. The memory may be configured to store the bitstream. The processor may be configured to obtain, from the bitstream, an indication of a number of channels specified in one or more layers in the bitstream, and obtain the channels specified in the one or more layers in the bitstream based on the indication of the number of channels.

Abstract: In general, techniques are described for signaling layers for scalable coding of higher order ambisonic audio data. A device comprising a memory and a processor may be configured to perform the techniques. The memory may be configured to store the bitstream. The processor may be configured to obtain, from the bitstream, an indication of a number of layers specified in the bitstream, and obtain the layers of the bitstream based on the indication of the number of layers.

Abstract: In general, techniques are directed to performing normalization with respect to ambient higher order ambisonic audio data. A device configured to decode higher order ambisonic audio data may perform the techniques. The device may include a memory and one or more processors. The memory may be configured to store an audio channel that provides a normalized ambient higher order ambisonic coefficient representative of at least a portion of an ambient component of a soundfield. The one or more processors may be configured to perform inverse normalization with respect to the audio channel.

Abstract: A device comprising a memory and one or more processors may be configured extract, from the bitstream, a type of quantization mode. The one or more processors may also be configured to switch, based on the type of quantization mode, between non-predictive vector dequantization to reconstruct a first set of one or more weights used to approximate the multi-directional V-Vector in the higher order ambisonics domain, and predictive vector dequantization to reconstruct a second set of one or more weights used to approximate the multi-directional V-Vector in the higher order ambisonics domain. The memory may be configured to store the reconstructed first set of one or more weights used to approximate the multi-directional V-Vector in the higher order ambisonics domain, and the reconstructed second set of one or more weights used to approximate the multi-directional V-Vector in the higher order ambisonics domain.

Abstract: In general, techniques are directed to intermediate compression of higher order ambisonic audio data. For example, a device comprising a processor and a memory may be configured to perform the techniques. The memory may be configured to store an intermediately formatted audio data generated as a result of an intermediate compression of higher order ambisonic audio data. The one or more processors may be configured to process the intermediately formatted audio data.

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 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 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 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 crossfading sets of spherical harmonic coefficients. An audio encoding device or audio decoding device comprising a memory and a processor may be configured to perform the techniques. The memory may be configured to store a first set of spherical harmonic coefficients (SHCs) and a second set of SHCs. The first set of SHCs describe a first sound field. The second set of SHCs describe a second sound field. The processor may be configured to crossfade between the first set of SHCs and a second set of SHCs to obtain a first set of crossfaded SHCs.

Abstract: In general, techniques are described for coding of vectors decomposed from higher-order ambisonic coefficients. A device comprising a memory and a processor may perform the techniques. The memory may be configured to store audio data. The processor may be configured to determine whether to perform vector dequantization or scalar dequantization with respect to a decomposed version of the plurality of HOA coefficients.

Abstract: In general, techniques are described for performing codebook selection when coding vectors decomposed from higher-order ambisonic coefficients. A device comprising a memory and a processor may perform the techniques. The memory may be configured to store a plurality of codebooks to use when performing vector dequantization with respect to a vector quantized spatial component of a soundfield. The vector quantized spatial component may be obtained through application of a decomposition to a plurality of higher order ambisonic coefficients. The processor may be configured to select one of the plurality of codebooks.

Abstract: In general, techniques are described for closed loop quantization of HOA coefficients that provide a three-dimensional representation of the sound field. An audio encoding device may perform closed loop quantization of an audio object based at least in part on a result of performing quantization of directional information associated with the audio object. An audio decoding device may obtain an audio object that has been closed loop quantized based at least in part on a result of performing quantization of directional information associated with the audio object, and may dequantize the audio object.

Abstract: In general, techniques are described for coding of vectors decomposed from higher order ambisonic coefficients. A device comprising a processor and a memory may perform the techniques. The processor may be configured to obtain from a bitstream data indicative of a plurality of weight values that represent a vector that is included in a decomposed version of the plurality of HOA coefficients. Each of the weight values may correspond to a respective one of a plurality of weights in a weighted sum of code vectors that represents the vector and that includes a set of code vectors. The processor may further be configured to reconstruct the vector based on the weight values and the code vectors. The memory may be configured to store the reconstructed vector.

Abstract: In general, techniques are described for inserting audio channels into descriptions of soundfields. A device comprising a processor may be configured to perform the techniques. The processor may be configured to obtain an audio channel separate from a higher-order ambisonic representation of a soundfield. The processor may further be configured to insert the audio channel at a spatial location within the soundfield such that the audio channel is able to be extracted from the soundfield.

Abstract: In general, techniques are described for low frequency rendering of higher-order ambisonic audio data. As an example, a device comprising a memory and a processor may perform the techniques. The memory may be configured to store higher-order ambisonic coefficients. The processor may be configured to obtain a renderer to be used when rendering the higher-order ambisonic coefficients into a speaker feed for a low frequency speaker.

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 signaling an order format for higher-order ambisonic audio data. An audio decoding device including a memory and a processor may perform the techniques. The memory may be configured to store a bitstream indicative of a coded higher-order ambisonic (HOA) audio signal. The processor may be configured to obtain, from the bitstream, a harmonic coefficient ordering format indicator indicative of a symmetric harmonic coefficient ordering format for a source set of HOA coefficients from which the coded HOA audio signal is generated. The processor may further be configured to decode the coded HOA audio signal based on the symmetric harmonic coefficient ordering format indicator.

Abstract: In general, techniques are described for coding an ambient higher order ambisonic coefficient. An audio decoding device comprising a memory and a processor may perform the techniques. The memory may store a first frame of a bitstream and a second frame of the bitstream. The processor may obtain, from the first frame, one or more bits indicative of whether the first frame is an independent frame that includes additional reference information to enable the first frame to be decoded without reference to the second frame. The processor may further obtain, in response to the one or more bits indicating that the first frame is not an independent frame, prediction information for first channel side information data of a transport channel. The prediction information may be used to decode the first channel side information data of the transport channel with reference to second channel side information data of the transport channel.

Abstract: In general, techniques are described for transitioning an ambient higher order ambisonic coefficient. A device comprising a memory and a processor may be configured to perform the techniques. The processor may obtain, from a frame of a bitstream of encoded audio data, a bit indicative of a reduced vector. The reduced vector may represent, at least in part, a spatial component of a sound field. The processor may also obtain, from the frame, a bit indicative of a transition of an ambient higher-order ambisonic coefficient. The ambient higher-order ambisonic coefficient may represent, at least in part, an ambient component of the sound field. The reduced vector may include a vector element associated with the ambient higher-order ambisonic coefficient in transition. The memory may be configured to store the frame of the bitstream.