Patent Description:
Audio plays a significant role in providing a content-rich multimedia experience in consumer electronics. The scalability and mobility of consumer electronic devices along with the growth of wireless connectivity provides users with instant access to content. Various audio reproduction systems can be used for playback over headphones or loudspeakers. In some examples, audio program content can include more than a stereo pair of audio signals, such as including surround sound or other multiple-channel configurations.

A conventional audio reproduction system can receive digital or analog audio source signal information from various audio or audio/video sources, such as a CD player, a TV tuner, a handheld media player, or the like. The audio reproduction system can include a home theater receiver or an automotive audio system dedicated to the selection, processing, and routing of broadcast audio and/or video signals. Audio output signals can be processed and output for playback over a speaker system. Such output signals can be two-channel signals sent to headphones or a pair of frontal loudspeakers, or multi-channel signals for surround sound playback. For surround sound playback, the audio reproduction system may include a multichannel decoder.

The audio reproduction system can further include processing equipment such as analog-to-digital converters for connecting analog audio sources, or digital audio input interfaces. The audio reproduction system may include a digital signal processor for processing audio signals, as well as digital-to-analog converters and signal amplifiers for converting the processed output signals to electrical signals sent to the transducers. The loudspeakers can be arranged in a variety of configurations as determined by various applications. Loudspeakers, for example, can be stand-alone units or can be incorporated in a device, such as in the case of consumer electronics such as a television set, laptop computer, hand held stereo, or the like. Due to technical and physical constraints, audio playback can be compromised or limited in such devices. Such limitations can be particularly evident in electronic devices having physical constraints where speakers are narrowly spaced apart, such as in laptops and other compact mobile devices. To address such audio constraints, various audio processing methods are used for reproducing two-channel or multi-channel audio signals over a pair of headphones or a pair of loudspeakers. Such methods include compelling spatial enhancement effects to improve the listener's experience.

Various techniques have been proposed for implementing audio signal processing based on Head-Related Transfer Functions (HRTF), such as for three-dimensional audio reproduction using headphones or loudspeakers. In some examples, the techniques are used for reproducing virtual loudspeakers localized in a horizontal plane with respect to a listener, or located at an elevated position with respect to the listener. To reduce horizontal localization artifacts for listener positions away from a "sweet spot" in a loudspeaker-based system, various filters can be applied to restrict the effect to lower frequencies.

Document <CIT> discloses an audio providing method that includes receiving an audio signal including a plurality of channels, applying an audio signal having a channel, from among the plurality of channels, giving a sense of elevation to a filter to generate a plurality of virtual audio signals to be respectively output to a plurality of speakers. The filter processes the audio signal to have a sense of elevation.

Document <CIT> discloses an audio providing apparatus that includes an object renderer configured to render an object audio signal based on geometric information regarding the object audio signal; a channel renderer configured to render an audio signal having a first channel number into an audio signal having a second channel number; and a mixer configured to mix the rendered object audio signal with the audio signal having the second channel number.

Document <CIT> discloses a method which decodes a downmix matrix for mapping a plurality of input channels of audio content to a plurality of output channels, the input and output channels being associated with respective speakers at predetermined positions relative to a listener position, wherein the downmix matrix is encoded by exploiting the symmetry of speaker pairs of the plurality of input channels and the symmetry of speaker pairs of the plurality of output channels.

Document <CIT> discloses an audio signal rendering method for reducing distortion of a sound image even when the layout of the arranged speakers is different from the standard layout.

Document <CIT> discusses reverberation generation for headphone virtualization, wherein one or more components of a binaural room impulse response (BRIR) for headphone virtualization are generated.

Document <CIT> discusses a system of rendering object-based audio content through a system that includes individually addressable drivers.

Document <CIT> shows a frequency-domain signal processing chain of a multi-channel audio decoder applying a first upmix/downmix unit, a decorrelator, and a second upmix/downmix unit.

The present invention provides for a method for providing virtualized audio information with the features of claim <NUM> and a system with the features of claim <NUM>. Embodiments of the invention are identified in the dependent claims.

Audio signal processing can be distributed across multiple processor circuits or software modules, such as in scalable systems or due to system constraints. For example, a TV audio system solution can include combined digital audio decoder and virtualizer post-processing modules so that an overall computational budget does not exceed the capacity of a single Integrated Circuit (IC) or System-On-Chip (SOC). To accommodate such a limitation, the decoder and virtualizer blocks can be implemented in separate cascaded hardware or software modules.

In an example, an internal I/O data bus, such as in TV audio system architecture, can be limited to <NUM> or <NUM> channels (e.g., corresponding to <NUM> or <NUM> surround sound systems). However, it can be desired or required to transmit a greater number of decoder output audio signals to a virtualizer input to provide a compelling immersive audio experience. The present inventors have thus recognized that a problem to be solved includes distributing audio signal processing across multiple processor circuits and/or devices to enable multi-dimensional audio reproduction of multiple-channel audio signals over loudspeakers or, in some examples, headphones. In an example, the problem can include using legacy hardware architecture with channel count limitations to distribute or process multi-dimensional audio information.

A solution to the above-described problem includes various methods for multi-dimensional audio reproduction using loudspeakers or headphones, such as can be used for playback of immersive audio content over sound bar loudspeakers, home theater systems, TVs, laptop computers, mobile or wearable devices, or other systems or devices. The methods and systems described herein can enable distribution of virtualization post-processing across two or more processor circuits or modules while reducing an intermediate transmitted audio channel count.

This overview is intended to provide a summary of the subject matter of the present patent application.

In the following description that includes examples of virtual environment rendering and audio signal processing, such as for reproduction via headphones or other loudspeakers, reference is made to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the inventions disclosed herein can be practiced.

As used herein, the phrase "audio signal" is a signal that is representative of a physical sound. Audio processing systems and methods described herein can include hardware circuitry and/or software configured to use or process audio signals using various filters. In some examples, the systems and methods can use signals from, or signals corresponding to, multiple audio channels. In an example, an audio signal can include a digital signal that includes information corresponding to multiple audio channels.

Various audio processing systems and methods can be used to reproduce two-channel or multi-channel audio signals over various loudspeaker configurations. For example, audio signals can be reproduced over headphones, over a pair of bookshelf loudspeakers, or over a surround sound or immersive audio system, such as using loudspeakers positioned at various locations with respect to a listener. Some examples can include or use compelling spatial enhancement effects to enhance a listening experience, such as where a number or orientation of physical loudspeakers is limited.

In <CIT>, entitled "Virtual Audio Processing for Loudspeaker or Headphone Playback", audio signals can be processed with a virtualizer processor circuit to create virtualized signals and a modified stereo image. Additionally or alternatively to the techniques in the '<NUM> patent, the present inventors have recognized that virtualization processing can be used to deliver an accurate sound field representation that includes various spatially-oriented components using a minimum number of loudspeakers.

In an example, relative virtualization filters, such as can be derived from head-related transfer functions, can be applied to render virtual audio information that is perceived by a listener as including sound information at various specified altitudes, or elevations, above or below a listener to further enhance a listener's experience. In an example, such virtual audio information is reproduced using a loudspeaker provided in a horizontal plane and the virtual audio information is perceived to originate from a loudspeaker or other source that is elevated relative to the horizontal plane, such as even when no physical or real loudspeaker exists in the perceived origination location. In an example, the virtual audio information provides an impression of sound elevation, or an auditory illusion, that extends from, and optionally includes, audio information in the horizontal plane. Similarly, virtualization filters can be applied to render virtual audio information perceived by a listener as including sound information at various locations within or among the horizontal plane, such as at locations that do not correspond to a physical location of a loudspeaker in the sound field.

<FIG> illustrates generally an example <NUM> of audio signal virtualization processing. In the example <NUM>, an input signal pair designated L<NUM> and R<NUM> are provided to a two-channel virtualizer module <NUM>. The two-channel virtualizer module <NUM> can include a first processor circuit configured to processes the input signal pair and provide an output signal pair designated LO and RO. In an example, the output signal pair is configured for playback using a stereo loudspeaker pair or headphones.

In an example, the virtualizer module <NUM> can be realized using a transaural shuffler topology such as when the input and output signal pairs represent information for loudspeakers that are symmetrically located relative to an anatomical median plane of a listener. In this example, sum and difference virtualization filters can be designated as shown in Equations (<NUM>) and (<NUM>), and can be applied by the first processor circuit in the two-channel virtualizer module <NUM>. <MAT> <MAT> In the example of Equations (<NUM>) and (<NUM>), dependence on frequency is omitted for simplification, and the following notations are used:.

In the case of headphone reproduction, H0c is substantially zero and H0i corresponds to a headphone-to-ear transfer function.

<FIG> illustrates generally an example <NUM> of a four-channel three-dimensional audio reproduction system. The example <NUM> can include or use virtualization processing to provide virtualized audio signal information for reproduction to a listener <NUM>. In the example <NUM>, a virtualization processor circuit <NUM> receives input signals L<NUM>, R<NUM>, L<NUM> and R<NUM> and applies virtualization processing to the input signals and renders or provides a fewer number of output signals than input signals. Binaural and transaural 3D audio virtualization algorithms can be used to process the various input signals, including sum and difference "shuffler"-based topologies that leverage properties such as left-right symmetry of channel layouts, minimum-phase models of head-related transfer functions (HRTFs) and spectral equalization methods, as well as digital IIR filter approximations. In an example, the virtualization processor circuit <NUM> receives the multiple input signals L<NUM>, R<NUM>, L<NUM> and R<NUM> from an audio decoder circuit, such as a surround sound decoder circuit, and renders substantially the same information using a pair of loudspeakers.

In <FIG>, the three-dimensional audio reproduction system or processor circuit <NUM> provides output signals designated LO and RO. Based on the virtualization processing, when the LO and RO signals are reproduced using a pair of loudspeakers (such as the loudspeakers corresponding to L and R in the example of <FIG>), audio information is perceived by the listener <NUM> as including information from multiple sources distributed about the loudspeaker environment. For example, when the LO and RO signals are reproduced using the speakers designated in the figure as L and R, the listener <NUM> can perceive audio signal information as originating from the left or right front speakers L<NUM> and R<NUM>, from the left or right rear speakers L<NUM> and R<NUM>, or from an intermediate location or phantom source somewhere between the speakers.

<FIG> illustrates generally an example <NUM> of multiple-stage virtualization processing. In an example, the three-dimensional audio reproduction system or processor circuit <NUM> from <FIG> can be implemented or applied using the virtualization processing in the example <NUM> of <FIG>. The example of <FIG> includes a first two-channel virtualizer module <NUM> and a second two-channel virtualizer module <NUM>. The first two-channel virtualizer module <NUM> is configured to receive a first input signal pair designated L<NUM> and R<NUM>, and the second two-channel virtualizer module <NUM> is configured to receive a second input signal pair designated L<NUM> and R<NUM>, In an example, L<NUM> and R<NUM> represent a front stereo pair and L<NUM> and R<NUM> represent a rear stereo pair (see, e.g., <FIG>). In other examples, L<NUM>, R<NUM>, L<NUM> and R<NUM> can represent other audio information such as for side, rear, or elevated sound signals, such as configured or designed for reproduction using a particular loudspeaker arrangement. In an example, the first two-channel virtualizer module <NUM> is configured to apply or use sum and difference virtualization filters, such as shown in Equation (<NUM>).

The second two-channel virtualizer module <NUM> can include a second processor circuit configured to receive the second input signal pair L<NUM> and R<NUM> and generate intermediate virtualized audio information as output signals designated L<NUM>,O and R<NUM>,O. In an example, the second two-channel virtualizer module <NUM> is configured to apply or use sum and difference virtualization filters, such as shown in Equation (<NUM>), to generate the intermediate virtualized output signals L<NUM>,O and R<NUM>,O. In an example, the second two-channel virtualizer module <NUM> is thus configured to provide or generate a partially virtualized signal, or multiple signals that are partially virtualized. The signal or signals are considered to be partially virtualized because the second two-channel virtualizer module <NUM> can be configured to provide virtualization processing in a limited manner. For example, the second two-channel virtualizer module <NUM> can be configured for horizontal plane virtualization processing, while vertical plane virtualization processing can be performed elsewhere or using a different device. The partially virtualized signals can be combined with one or more other virtualized or non-virtualized signals before reproduction to a listener. In an example, the second two-channel virtualizer module <NUM> can apply or use the functions described in Equations <NUM> and <NUM> to provide the intermediate virtualized output signals. <MAT> <MAT> In the example of Equations (<NUM>) and (<NUM>), dependence on frequency is omitted for simplification, and the following notations are used:.

In the example of <FIG>, the intermediate virtualized output signals L<NUM>,O and R<NUM>,O are combined with the first input signal pair designated L<NUM> and R<NUM> prior to virtualization of the first input signal pair designated L<NUM> and R<NUM>. The combined signals are then further processed or virtualized using the first two-channel virtualizer module <NUM>. The first and second two-channel virtualizer modules <NUM> and <NUM> can be configured to apply different virtualization processing such as to achieve different virtualization effects. For example, the first two-channel virtualizer module <NUM> can be configured to provide horizontal-plane virtualization processing, and the second two-channel virtualizer module <NUM> can be configured to provide vertical-plane virtualization processing. Other types of virtualization processing can similarly be used or applied using the different modules.

The present inventors have recognized that a result of virtualization processing by modules <NUM> and <NUM> and combining the intermediate signals according to the example of <FIG> is substantially equivalent to virtualization processing by both modules independently. <FIG>, for example, illustrates generally an example <NUM> that includes independent virtualization processing by first and second two-channel virtualizer modules <NUM> and <NUM>. In the example of <FIG>, the first two-channel virtualizer module <NUM> receives the input signal pair designated L<NUM> and R<NUM> and generates a partially virtualized output signal pair designated L<NUM>,O and R<NUM>,O, and the second two-channel virtualizer module <NUM> receives the input signal pair designated L<NUM> and R<NUM> and generates a partially virtualized output signal pair designated L<NUM>,O and R<NUM>,O. The example <NUM> of <FIG> further includes a summing module <NUM> that includes a circuit configured to sum the partially virtualized output signal pairs L<NUM>,O and R<NUM>,O, and L<NUM>,O and R<NUM>,O to provide the virtualized output signals LO and RO.

In the example of <FIG>, the first two-channel virtualizer module <NUM> is configured to apply the sum and difference virtualization filters as shown in Equations (<NUM>) and (<NUM>), and as similarly described above in the example of the two-channel virtualizer module <NUM> from <FIG>. The second two-channel virtualizer module <NUM> is configured to apply sum and different virtualization filters as shown in Equations (<NUM>) and (<NUM>). <MAT> <MAT>.

By comparing Equations (<NUM>) and (<NUM>) with Equations (<NUM>) and (<NUM>), it can be observed that the four-channel pairwise virtualizer examples of <FIG> are substantially the same.

<FIG> illustrates generally an example <NUM> that includes virtualization processing by first and second two-channel virtualizer modules <NUM> and <NUM>. In the example of <FIG>, the second two-channel virtualizer module <NUM> receives the input signal pair designated L<NUM> and R<NUM> and generates a partially virtualized output signal pair designated L<NUM>,O and R<NUM>,O. The example <NUM> of <FIG> further includes a summing module <NUM> that includes a circuit configured to sum the partially virtualized output signal pair L<NUM>,O and R<NUM>,O with an input signal pair L<NUM> and R<NUM> and provide the summed signals to the first two-channel virtualizer module <NUM>. The first two-channel virtualizer module <NUM> receives the summed signal pair and generates the virtualized output signals LO and RO.

In the example of <FIG>, the first two-channel virtualizer module <NUM> is configured to apply the sum and difference virtualization filters as shown in Equations (<NUM>) and (<NUM>), and as similarly described above in the example of the two-channel virtualizer module <NUM> from <FIG>. The second two-channel virtualizer module <NUM> is configured to apply sum and different virtualization filters as shown in Equation (<NUM>).

The example of <FIG> thus illustrates generally a simplified version of the four-channel virtualizer of <FIG>, wherein the second two-channel virtualizer module <NUM> applies the same filter to both input signals when the transfer functions H<NUM>/<NUM>,SUM and H<NUM>/<NUM>,DlFF are approximately equal, that is, when ipsilateral and contralateral HRTF ratios are approximately equal.

Any one or more of the virtualization processing examples described herein can include or use decorrelation processing. For example, any one of more of the virtualizer modules from <FIG>, <FIG>, and/or <NUM>, can include or use a decorrelator circuit configured to decorrelate one or more of the audio input signals. In an example, a decorrelator circuit precedes at least one input of a virtualizer module such that the virtualizer module processes signal pairs that are decorrelated from each other. Further examples and discussion about decorrelation processing are provided below.

<FIG> illustrates generally an example <NUM> of a block diagram that shows virtualization processing of multiple audio signals. The example <NUM> includes a first audio signal processing device <NUM> coupled to a second audio signal processing device <NUM> using a data bus circuit <NUM>.

The first audio signal processing device <NUM> can include a decoder circuit <NUM>. In an example, the decoder circuit <NUM> receives a multiple-channel input signal <NUM> that includes digital or analog signal information. In an example, the multiple-channel input signal <NUM> includes a digital bit stream that includes information about multiple audio signals. In an example, the multiple-channel input signal <NUM> includes audio signals for a surround sound or an immersive audio program. In an example, an immersive audio program can include nine or more channels, such as in the DIS:X <NUM>. 1ch format. In an example, the immersive audio program includes eight channels, including left and right front channels (L<NUM> and R<NUM>), a center channel (C), a low frequency channel (Lfe), left and right rear channels (L<NUM> and R<NUM>), and left and right elevation channels (L<NUM> and R<NUM>). Additional or fewer channels or signals can similarly be used.

The decoder circuit <NUM> can be configured to decode the multiple-channel input signal <NUM> and provide a decoder output <NUM>. The decoder output <NUM> can include multiple discrete channels of information. For example, when the multiple-channel input signal <NUM> includes information about an <NUM> immersive audio program, then the decoder output <NUM> can include audio signals for twelve discrete audio channels. In an example, the bus circuit <NUM> includes at least twelve channels and transmits all of the audio signals from the first audio signal processing device <NUM> to the second audio signal processing device <NUM> using respective channels. The second audio signal processing device <NUM> can include a virtualization processor circuit <NUM> that is configured to receive one or more of the signals from the bus circuit <NUM>. The virtualization processor circuit <NUM> can process the received signals, such as using one or more HRTFs or other filters, to generate an audio output signal <NUM> that includes virtualized audio signal information. In an example, the audio output signal <NUM> includes a stereo output pair of audio signals (e.g., LO and RO) configured for reproduction using a pair of loudspeakers in a listening environment, or using headphones. In an example, the first or second audio signal processing device <NUM> or <NUM> can apply one or more filters or functions to accommodate artifacts related to the listening environment to further enhance a listener's experience or perception of virtualized components in the audio output signal <NUM>.

In some audio signal processing devices, particularly at the consumer-grade level, the bus circuit <NUM> can be limited to a specified or predetermined number of discrete channels. For example, some devices can be configured to accommodate up to, but not greater than, six channels (e.g., corresponding to a <NUM> surround system). When audio program information includes greater than, e.g., six channels of information, then at least a portion of the audio program can be lost if the program information is transmitted using the bus circuit <NUM>. In some examples, the lost information can be critical to the overall program or listener experience. The present inventors have recognized that this channel count problem can be solved using distributed virtualization processing.

<FIG> illustrates generally an example <NUM> that includes a distributed audio virtualization system. The example <NUM> can be used to provide multiple-channel immersive audio rendering such as using physical loudspeakers or headphones. The example <NUM> includes a first audio signal processing device <NUM> coupled to a second audio signal processing device <NUM> using a second data bus circuit <NUM>. In an example, the second data bus circuit <NUM> includes the same bandwidth as is provided by the data bus circuit <NUM> in the example of <FIG>. That is, the second data bus circuit <NUM> can include a bandwidth that is lower than may be required to carry all of the information about the multiple-channel input signal <NUM>.

In the example of <FIG>, the first audio signal processing device <NUM> can include the decoder circuit <NUM> and a first virtualization processor circuit <NUM>. In an example, the decoder circuit <NUM> receives the multiple-channel input signal <NUM>, such as can include digital or analog signal information. As similarly explained above in the example of <FIG>, the multiple-channel input signal <NUM> includes a digital bit stream that includes information about multiple audio signals, and can, in an example, include audio signals for an immersive audio program.

The decoder circuit <NUM> can be configured to decode the multiple-channel input signal <NUM> and provide the decoder output <NUM>. The decoder output <NUM> can include multiple discrete channels of information. For example, when the multiple-channel input signal <NUM> includes information about an immersive audio program (e.g., <NUM> format), then the decoder output <NUM> can include audio signals for, e.g., twelve discrete audio channels. In an example, the bus circuit <NUM> includes fewer than twelve channels and thus cannot transmit each of the audio signals from the first audio signal processing device <NUM> to the second audio signal processing device <NUM>.

In an example, the decoder output <NUM> can be partially virtualized by the first audio signal processing device <NUM>, such as using the first virtualization processor circuit <NUM>. For example, the first virtualization processor circuit <NUM> can include or use the example <NUM> of <FIG>, the example <NUM> of <FIG>, or the example <NUM> of <FIG>, to receive multiple input signals, apply first virtualization processing to at least a portion of the received input signals to render or provide intermediate virtualized audio information, and then combine the intermediate virtualized audio information with one or more others of the input signals.

Referring now to <FIG> and to <FIG> as a representative and nonlimiting example, the multiple-channel input signal <NUM> (see <FIG>) can include the input signal pairs designated L<NUM>, R<NUM>, L<NUM> and R<NUM> (see <FIG>). The first virtualization processor circuit <NUM> can receive at least the input signal pair designated L<NUM> and R<NUM> and can perform first virtualization processing on the signal pair. According to the invention, the first virtualization processor circuit <NUM> applies first HRTF filters to one or more of the L<NUM> and R<NUM> signals to render or generate the partially virtualized output signal pair designated L<NUM>,O and R<NUM>,O. The first virtualization processor circuit or a designated summing module can receive the partially virtualized output signal pair L<NUM>,O and R<NUM>,O and sum the partially virtualized output signal pair L<NUM>,O and R<NUM>,O with the other input signal pair L<NUM> and R<NUM>. Following the summation of the signals, fewer than four audio signal channels are provided by the first audio signal processing device <NUM> to the second data bus circuit <NUM>. Thus, in an example where the multiple-channel input signal <NUM> includes four audio signals, the second data bus circuit <NUM> can be used to transmit partially virtualized information from the first audio signal processing device <NUM> to another device, such as without a loss of information.

In the example of <FIG>, the second data bus circuit <NUM> provides the partially virtualized information to the second audio signal processing device <NUM>. The second audio signal processing device <NUM> can further process the received signals using a second virtualization processor circuit <NUM> and generate further virtualized output signals (e.g., output signals LO and RO in the example of <FIG>).

The second virtualization processor circuit <NUM> can be configured to receive one or more of the signals from the second data bus circuit <NUM>. The second virtualization processor circuit <NUM> can process the received signals, according to the invention using one or more HRTFs, to generate an audio output signal <NUM> that includes virtualized audio signal information. In an example, the audio output signal <NUM> includes a stereo output pair of audio signals (e.g., LO and RO from the example of <FIG>) configured for reproduction using a pair of loudspeakers in a listening environment, or using headphones. In an example, the first or second audio signal processing device <NUM> or <NUM> can apply one or more filters or functions to accommodate artifacts related to the listening environment to further enhance a listener's experience or perception of virtualized components in the audio output signal <NUM>.

In other words, the example of <FIG> illustrates generally a first audio signal processing device <NUM> that includes a first virtualization processor circuit <NUM> that is configured to process or "virtualize" information from one or more channels in the multiple-channel input signal <NUM> to provide one or more corresponding intermediate virtualized signals. The intermediate virtualized signals can then be combined with one or more other channels in the multiple-channel input signal <NUM> to provide a partially virtualized audio program that includes fewer channels than were included in the multiple-channel input signal <NUM>. That is, the first virtualization processor circuit <NUM> can receive an audio program that includes a first number of channels, then apply virtualization processing and render a fewer number of channels than were originally received with the audio program, such as without losing the information or fidelity provided by the other channels. The partially virtualized audio program can be transmitted using the second data bus circuit <NUM> without a loss of information, and the transmitted information can be further processed or further virtualized using another virtualization processor (e.g., using the second audio signal processing device <NUM> and/or the second virtualization processor circuit <NUM>), such as before output to a sound reproduction system such as physical loudspeakers or headphones.

In an example, a method for providing virtualized audio information using the system of <FIG> includes receiving audio program information that includes at least N discrete audio signals, such as corresponding to the multiple-channel input signal <NUM>. The method can include generating intermediate virtualized audio information such as using the first virtualization processor circuit <NUM> using at least a portion of the received audio program information. For example, generating the intermediate virtualized audio information can include applying a first virtualization filter ( based on an HRTF) to M of the N audio signals to provide a first virtualization filter output and providing the intermediate virtualized audio information using the first virtualization filter output. In an example, the intermediate virtualized audio information comprises J discrete audio signals, and J is less than N. In an example, M is less than or equal to N. The method can further include transmitting the intermediate virtualized audio information using the second data bus circuit <NUM> to the second virtualization processor circuit <NUM>, and the second data bus circuit <NUM> can have fewer than N channels. In an example, the second virtualization processor circuit <NUM> can be configured to generate further virtualized audio information by applying a different second virtualization filter to one or more of the J audio signals. For example, the first virtualization processor circuit <NUM> can be configured to apply horizontal-plane virtualization to at least the L<NUM> and R<NUM> signals to render or provide virtualized signals L<NUM>,O and R<NUM>,O, such as can be combined with other input signals L<NUM> and R<NUM> and transmitted using the second data bus circuit <NUM>. The second virtualization processor circuit <NUM> can be configured to apply other virtualization processing (e.g., vertical-plane virtualization) to the combined signals received from the second data bus circuit <NUM> to provide virtualized output signals for reproduction via loudspeakers or headphones.

<FIG> illustrates generally an example <NUM> of a first system configured to perform distributed virtualization processing on various audio signals. The example <NUM> includes a first audio processing module <NUM> coupled to a second audio processing module <NUM> using a third data bus circuit <NUM>. The first audio processing module <NUM> is configured to receive various pairwise input signals <NUM>, apply first virtualization processing and reduce a total audio signal or channel count by combining one or more signals or channels following the first virtualization processing. The first audio processing module <NUM> provides the reduced number of signals or channels to the second audio processing module <NUM> using the third data bus circuit <NUM>. The second audio processing module <NUM> applies second virtualization processing and renders, in the example of <FIG>, a pairwise output signal <NUM>. In an example, the multiple pairwise input signals <NUM> include various channels that can receive immersive audio program information, including signal channels L<NUM> and R<NUM> (e.g., corresponding to a front stereo pair), L<NUM> and R<NUM> (e.g., corresponding to a rear stereo pair), L<NUM> and R<NUM> (e.g., corresponding to a height or elevated stereo pair), a center channel C, and a low frequency channel Lfe. The pairwise output signal <NUM> can include a stereo output pair of signals designated LO and RO. Other channel types or designations can similarly be used.

In the example <NUM>, the first audio processing module <NUM> includes first stage virtualization processing by a first processor circuit <NUM> that receives input signals L<NUM> and R<NUM>, such as corresponding to height audio signals. The first processor circuit <NUM> includes a decorrelator circuit that is configured to apply decorrelation processing to at least one of the input signals L<NUM> and R<NUM>, such as to enhance spatialization processing and reduce an occurrence of audio artifacts in the processed signals. Following the decorrelator circuit, the decorrelated input signals are processed or virtualized such as using a two-channel virtualizer module (see, e.g., the second two-channel virtualizer module <NUM> from the example of <FIG> and Equation (<NUM>)). Following the first processor circuit <NUM>, output signals from the first processor circuit <NUM> can be combined with one or more others of the input signals <NUM>. For example, as shown in <FIG>, the output signals from the first processor circuit <NUM> can be combined or summed with the L<NUM> and R<NUM> signals, such as using a summing circuit <NUM>, to render signals L<NUM>,<NUM> and R<NUM>,<NUM>. One or more others of the input signals <NUM> can be processed using the first audio processing module <NUM>, however, discussion of such other processing is omitted for brevity and simplicity of the present illustrative example. With the partially-virtualized L<NUM> and R<NUM> signals combined with the input signals L<NUM> and R<NUM> to provide signals L<NUM>,<NUM> and R<NUM>,<NUM>, the first audio processing module <NUM> can thus provide six output signals (e.g., designated L<NUM>,<NUM>, R<NUM>,<NUM>, L<NUM>, R<NUM>, C, and Lfe in the example of <FIG>) to the third data bus circuit <NUM>.

The third data bus circuit <NUM> can transmit the six signals to the second audio processing module <NUM>. In the example, the second audio processing module <NUM> includes multiple second-stage virtualization processing circuits, including a second processor circuit <NUM>, third processor circuit <NUM>, and fourth processor circuit <NUM>. In the illustration, the second through fourth processor circuits <NUM>-<NUM> are shown as discrete processors however processing operations for one or more the circuits can be combined or performed using one or more physical processing circuits. The second processor circuit <NUM> is configured to receive the signals L<NUM>,<NUM>, and R<NUM>,<NUM>, the third processor circuit <NUM> is configured to receive the signals L<NUM>, and R<NUM>, and the fourth processor circuit <NUM> is configured to receive the signals C, and Lfe. The outputs of the second through fourth processor circuits <NUM>-<NUM> are provided to a second summing circuit <NUM> that is configured to sum output signals from the various processor circuits to render the pairwise output signal <NUM>, designated LO and RO.

In the example of <FIG>, the second processor circuit <NUM> receives input signals L<NUM>,<NUM>, and R<NUM>,<NUM>, such as corresponding to a combination of the virtualized height audio signals from the first processor circuit <NUM> and the L<NUM> and R<NUM> signals as received by the first audio processing module <NUM>. The second processor circuit <NUM> includes according to the invention a decorrelator circuit that is configured to apply decorrelation processing to at least one of the input signals L<NUM>,<NUM> and R<NUM>,<NUM>, such as to enhance spatialization processing and reduce an occurrence of audio artifacts in the processed signals. Following the decorrelator circuit, the decorrelated signals are processed or virtualized such as using a two-channel virtualizer module (see the first two-channel virtualizer module <NUM> from the example of <FIG> and Equations (<NUM> and <NUM>)).

The fourth processor circuit <NUM> can optionally include a decorrelator circuit (not shown) that is configured to apply decorrelation processing to at least one of the input signals L<NUM> and R<NUM>, such as to enhance spatialization processing and reduce an occurrence of audio artifacts in the processed signals. The input signals L<NUM> and R<NUM> are processed or virtualized such as using a two-channel virtualizer module (see, e.g., the second two-channel virtualizer module <NUM> from the example of <FIG> and Equations (<NUM> and <NUM>)). In the example of <FIG>, the third processor circuit <NUM> is configured to receive and process the C and Lfe signals, such as optionally using an all-pass filter and/or decorrelation processing.

The example of <FIG> thus illustrates a pairwise multi-channel virtualizer for two-channel output, such as over a frontal loudspeaker pair (see, e.g., <FIG>) using pairwise virtualization processing, such as illustrated in <FIG> and <FIG>. In this example, the height channel pair (L<NUM>, R<NUM>) is processed using a first-stage virtualizer including a decorrelator. This virtualizer topology, including using a designated virtual height filter implemented by the first processor circuit <NUM>, can be computationally advantageous because it enables sharing horizontal-plane virtualization processing with the front input signal pair. In addition, the illustrated topology allows an effectiveness or degree of the virtual height effect to be optimized or tuned, such as independently of the horizontal-plane or other virtualization processing.

<FIG> illustrates generally an example <NUM> of a second system configured to perform distributed virtualization processing on various audio signals. The example <NUM> includes a third audio processing module <NUM> coupled to a fourth audio processing module <NUM> using the third data bus circuit <NUM>. The example of <FIG> includes or uses some of the same circuitry and processing as described above in the example <NUM> from <FIG>.

For example, the third audio processing module <NUM> is configured to receive the various pairwise input signals <NUM>, apply virtualization processing and reduce a total audio signal or channel count by combining one or more signals or channels following the virtualization processing. The third audio processing module <NUM> provides the reduced number of signals or channels to the fourth audio processing module <NUM> using the six-channel, third data bus circuit <NUM>. The fourth audio processing module <NUM> applies other virtualization processing and renders, in the example of <FIG>, a pairwise output signal <NUM>. In an example, the pairwise output signals <NUM> and <NUM> from the examples of <FIG> and <FIG> can be substantially the same when the various modules and processors are configured to provide substantially the same virtualization processing, however, in a different order and by operating on different base signals or combinations of signals.

In the example <NUM>, the third audio processing module <NUM> includes first stage virtualization processing by the fourth processor circuit <NUM>. That is, the fourth processor circuit <NUM> receives input signals L<NUM> and R<NUM>, such as corresponding to rear stereo audio signals. Following the fourth processor circuit <NUM>, output signals from the fourth processor circuit <NUM> can be combined with one or more others of the input signals <NUM>. For example, as shown in <FIG>, the output signals from the fourth processor circuit <NUM> can be combined or summed with the L<NUM> and R<NUM> signals, such as using a first summing circuit <NUM>, to render signals L<NUM>,<NUM> and R<NUM>,<NUM>. One or more others of the input signals <NUM> can be processed using the third audio processing module <NUM>, however, discussion of such other processing is omitted for brevity and simplicity of the present illustrative example. With the partially-virtualized L<NUM> and R<NUM> signals combined with the input signals L<NUM> and R<NUM> to provide signals L<NUM>,<NUM> and R<NUM>,<NUM>, the fourth audio processing module <NUM> can thus provide six output signals (e.g., designated L<NUM>,<NUM>, R<NUM>,<NUM>, L<NUM>, R<NUM>, C, and Lfe in the example of <FIG>) to the third data bus circuit <NUM>.

The third data bus circuit <NUM> can transmit the six signals to the fourth audio processing module <NUM>. In the example, the fourth audio processing module <NUM> includes multiple second-stage virtualization processing circuits, including the first processor circuit <NUM>, the second processor circuit <NUM>, and the third processor circuit <NUM>. In the illustration, the first, second, and third processor circuits <NUM>, <NUM>, and <NUM>, are shown as discrete processors however processing operations for one or more the circuits can be combined or performed using one or more physical processing circuits in the fourth audio processing module <NUM>. The second processor circuit <NUM> is configured to receive the signals L<NUM>,<NUM>, and R<NUM>,<NUM>, the first processor circuit <NUM> is configured to receive the signals L<NUM>, and R<NUM>, and the third processor circuit <NUM> is configured to receive the signals C, and Lfe. Virtualized outputs from the first processor circuit <NUM> are provided to a second summing circuit <NUM>, where the outputs are summed with the received signals L<NUM>,<NUM>, and R<NUM>,<NUM> from the third data bus circuit <NUM> and then provided to the second processor circuit <NUM>. In this example, the second processor circuit <NUM> applies virtualization processing to a combination of the L<NUM>, R<NUM>, and the L<NUM> and R<NUM>, signals after such signals have received other virtualization processing by the first and fourth processor circuits <NUM> and <NUM>. Following processing in the fourth audio processing module <NUM>, the outputs of the first, second, and third processor circuits <NUM>, <NUM>, and <NUM> are provided to a third summing circuit <NUM> that is configured to sum output signals from the various processor circuits to render the pairwise output signal <NUM>, designated LO and RO.

<FIG> and <FIG> thus illustrate examples of pairwise, multi-channel virtualization processing system for two-channel output, such as over a frontal loudspeaker pair (see, e.g., <FIG>). The examples include pairwise virtualization processing, such as illustrated in <FIG> and <FIG>. In the example of <FIG>, the height channel pair (L<NUM>, R<NUM>) is processed using a first-stage virtualizer including a decorrelator. This virtualizer topology, including using a designated virtual height filter implemented by the first processor circuit <NUM>, can be computationally advantageous because it enables sharing horizontal-plane virtualization processing with the front input signal pair. In addition, the illustrated topology allows an effectiveness or degree of the virtual height effect to be optimized or tuned, such as independently of the horizontal-plane or other virtualization processing. In the example of <FIG>, the rear stereo channel pair (L<NUM>, R<NUM>) is processed using a first-stage virtualizer. This virtualizer topology, including using a designated virtual horizontal-plane filter implemented by the fourth processor circuit <NUM>, can be computationally advantageous because it enables sharing height or other virtualization processing with the front input signal pair. Similarly to the example of <FIG>, the illustrated topology of <FIG> optimizes tuning flexibility for virtualization processing in multiple different planes. For example, when the example of <FIG> is applied to render a two-channel output for headphone audio, this virtualizer topology provides independent tuning of virtual front and virtual rear effects over headphones for individual listeners, such as can be helpful to minimize occurrences of front-back confusion, spurious elevation errors, and to maximize perceived externalization.

Some modules or processors discussed herein are configured to apply or use signal decorrelation processing, such as prior to virtualization processing. Decorrelation is an audio processing technique that reduces a correlation between two or more audio signals or channels. In some examples, decorrelation can be used to modify a listener's perceived spatial imagery of an audio signal. Other examples of using decorrelation processing to adjust or modify spatial imagery or perception can include decreasing a perceived "phantom" source effect between a pair of audio channels, widening a perceived distance between a pair of audio channels, improving a perceived externalization of an audio signal when it is reproduced over headphones, and/or increasing a perceived diffuseness in a reproduced sound field.

By applying decorrelation processing to a left/right signal pair prior to virtualization, source signals panned between the left and right input channels will be heard by the listener at virtual positions substantially located on a shortest arc centered on the listener's position and joining the due positions of the virtual loudspeakers. The present inventors have realized that such decorrelation processing can be effective in avoiding various virtual localization artifacts, such as in-head localization, front-back confusion, and elevation errors.

In an example, decorrelation processing can be carried out using, among other things, an all-pass filter. The filter can be applied to at least one of the input signals and, in an example, can be realized by a nested all-pass filter. Interchannel decorrelation can be provided by choosing different settings or values of different components of the filter. Various other designs for decorrelation filters can similarly be used.

In an example, a method for reducing correlation between two (or more) audio signals includes randomizing a phase of each audio signal. For example, respective all-pass filters, such as each based upon different random phase calculations in the frequency domain, can be used to filter each audio signal. In some examples, decorrelation can introduce timbral changes or other unintended artifacts into the audio signals, which can be separately addressed.

Various systems and machines can be configured to perform or carry out one or more of the signal processing tasks described herein. For example, any one or more of the virtualization processing modules or virtualization processor circuits, decorrelation circuits, virtualization or spatialization filters, or other modules or processes, can be implemented using a general-purpose machine or using a special, purpose-built machine that performs the various processing tasks, such as using instructions retrieved from a tangible, non-transitory, processor-readable medium.

<FIG> is a block diagram illustrating components of a machine <NUM>, according to some example embodiments, able to read instructions <NUM> from a machine-readable medium (e.g., a machine-readable storage medium) and perform any one or more of the methodologies discussed herein. Specifically, <FIG> shows a diagrammatic representation of the machine <NUM> in the example form of a computer system, within which the instructions <NUM> (e.g., software, a program, an application, an applet, an app, or other executable code) for causing the machine <NUM> to perform any one or more of the methodologies discussed herein may be executed. For example, the instructions <NUM> can implement modules or circuits or components of <FIG>, and FIGS. <NUM>-<NUM>, and so forth. The instructions <NUM> can transform the general, non-programmed machine <NUM> into a particular machine programmed to carry out the described and illustrated functions in the manner described (e.g., as an audio processor circuit). In alternative embodiments, the machine <NUM> operates as a standalone device or can be coupled (e.g., networked) to other machines. In a networked deployment, the machine <NUM> can operate in the capacity of a server machine or a client machine in a server-client network environment, or as a peer machine in a peer-to-peer (or distributed) network environment.

The machine <NUM> can comprise, but is not limited to, a server computer, a client computer, a personal computer (PC), a tablet computer, a laptop computer, a netbook, a set-top box (STB), a personal digital assistant (PDA), an entertainment media system or system component, a cellular telephone, a smart phone, a mobile device, a wearable device (e.g., a smart watch), a smart home device (e.g., a smart appliance), other smart devices, a web appliance, a network router, a network switch, a network bridge, a headphone driver, or any machine capable of executing the instructions <NUM>, sequentially or otherwise, that specify actions to be taken by the machine <NUM>. Further, while only a single machine <NUM> is illustrated, the term "machine" shall also be taken to include a collection of machines <NUM> that individually or jointly execute the instructions <NUM> to perform any one or more of the methodologies discussed herein.

The machine <NUM> can include or use processors <NUM>, such as including an audio processor circuit, non-transitory memory/storage <NUM>, and I/O components <NUM>, which can be configured to communicate with each other such as via a bus <NUM>. In an example embodiment, the processors <NUM> (e.g., a central processing unit (CPU), a reduced instruction set computing (RISC) processor, a complex instruction set computing (CISC) processor, a graphics processing unit (GPU), a digital signal processor (DSP), an ASIC, a radiofrequency integrated circuit (RFIC), another processor, or any suitable combination thereof) can include, for example, a circuit such as a processor <NUM> and a processor <NUM> that may execute the instructions <NUM>. The term "processor" is intended to include a multi-core processor <NUM>, <NUM> that can comprise two or more independent processors <NUM>, <NUM> (sometimes referred to as "cores") that may execute the instructions <NUM> contemporaneously. Although <FIG> shows multiple processors <NUM>, the machine <NUM> may include a single processor <NUM>, <NUM> with a single core, a single processor <NUM>, <NUM> with multiple cores (e.g., a multi-core processor <NUM>, <NUM>), multiple processors <NUM>, <NUM> with a single core, multiple processors <NUM>, <NUM> with multiples cores, or any combination thereof, wherein any one or more of the processors can include a circuit configured to apply a height filter to an audio signal to render a processed or virtualized audio signal.

The memory/storage <NUM> can include a memory <NUM>, such as a main memory circuit, or other memory storage circuit, and a storage unit <NUM>, both accessible to the processors <NUM> such as via the bus <NUM>. The storage unit <NUM> and memory <NUM> store the instructions <NUM> embodying any one or more of the methodologies or functions described herein. The instructions <NUM> may also reside, completely or partially, within the memory <NUM>, within the storage unit <NUM>, within at least one of the processors <NUM> (e.g., within the cache memory of processor <NUM>, <NUM>), or any suitable combination thereof, during execution thereof by the machine <NUM>. Accordingly, the memory <NUM>, the storage unit <NUM>, and the memory of the processors <NUM> are examples of machine-readable media.

As used herein, "machine-readable medium" means a device able to store the instructions <NUM> and data temporarily or permanently and may include, but not be limited to, random-access memory (RAM), read-only memory (ROM), buffer memory, flash memory, optical media, magnetic media, cache memory, other types of storage (e.g., erasable programmable read-only memory (EEPROM)), and/or any suitable combination thereof. The term "machine-readable medium" should be taken to include a single medium or multiple media (e.g., a centralized or distributed database, or associated caches and servers) able to store the instructions <NUM>. The term "machine-readable medium" shall also be taken to include any medium, or combination of multiple media, that is capable of storing instructions (e.g., instructions <NUM>) for execution by a machine (e.g., machine <NUM>), such that the instructions <NUM>, when executed by one or more processors of the machine <NUM> (e.g., processors <NUM>), cause the machine <NUM> to perform any one or more of the methodologies described herein. Accordingly, a "machine-readable medium" refers to a single storage apparatus or device, as well as "cloud-based" storage systems or storage networks that include multiple storage apparatus or devices. The term "machine-readable medium" excludes signals per se.

The I/O components <NUM> may include a variety of components to receive input, provide output, produce output, transmit information, exchange information, capture measurements, and so on. The specific I/O components <NUM> that are included in a particular machine <NUM> will depend on the type of machine <NUM>. For example, portable machines such as mobile phones will likely include a touch input device or other such input mechanisms, while a headless server machine will likely not include such a touch input device. It will be appreciated that the I/O components <NUM> may include many other components that are not shown in <FIG>. The I/O components <NUM> are grouped by functionality merely for simplifying the following discussion, and the grouping is in no way limiting. In various example embodiments, the I/O components <NUM> may include output components <NUM> and input components <NUM>. The output components <NUM> can include visual components (e.g., a display such as a plasma display panel (PDP), a light emitting diode (LED) display, a liquid crystal display (LCD), a projector, or a cathode ray tube (CRT)), acoustic components (e.g., loudspeakers), haptic components (e.g., a vibratory motor, resistance mechanisms), other signal generators, and so forth. The input components <NUM> can include alphanumeric input components (e.g., a keyboard, a touch screen configured to receive alphanumeric input, a photo-optical keyboard, or other alphanumeric input components), point based input components (e.g., a mouse, a touchpad, a trackball, a joystick, a motion sensor, or other pointing instruments), tactile input components (e.g., a physical button, a touch screen that provides location and/or force of touches or touch gestures, or other tactile input components), audio input components (e.g., a microphone), and the like.

In further example embodiments, the I/O components <NUM> can include biometric components <NUM>, motion components <NUM>, environmental components <NUM>, or position components <NUM>, among a wide array of other components. For example, the biometric components <NUM> can include components to detect expressions (e.g., hand expressions, facial expressions, vocal expressions, body gestures, or eye tracking), measure biosignals (e.g., blood pressure, heart rate, body temperature, perspiration, or brain waves), identify a person (e.g., voice identification, retinal identification, facial identification, fingerprint identification, or electroencephalogram based identification), and the like, such as can influence a inclusion, use, or selection of a listener-specific or environment-specific impulse response or HRTF, for example. In an example, the biometric components <NUM> can include one or more sensors configured to sense or provide information about a detected location of the listener <NUM> in an environment. The motion components <NUM> can include acceleration sensor components (e.g., accelerometer), gravitation sensor components, rotation sensor components (e.g., gyroscope), and so forth, such as can be used to track changes in the location of the listener <NUM>. The environmental components <NUM> can include, for example, illumination sensor components (e.g., photometer), temperature sensor components (e.g., one or more thermometers that detect ambient temperature), humidity sensor components, pressure sensor components (e.g., barometer), acoustic sensor components (e.g., one or more microphones that detect reverberation decay times, such as for one or more frequencies or frequency bands), proximity sensor or room volume sensing components (e.g., infrared sensors that detect nearby objects), gas sensors (e.g., gas detection sensors to detect concentrations of hazardous gases for safety or to measure pollutants in the atmosphere), or other components that may provide indications, measurements, or signals corresponding to a surrounding physical environment. The position components <NUM> can include location sensor components (e.g., a Global Position System (GPS) receiver component), altitude sensor components (e.g., altimeters or barometers that detect air pressure from which altitude may be derived), orientation sensor components (e.g., magnetometers), and the like.

Communication can be implemented using a wide variety of technologies. The I/O components <NUM> can include communication components <NUM> operable to couple the machine <NUM> to a network <NUM> or devices <NUM> via a coupling <NUM> and a coupling <NUM> respectively. For example, the communication components <NUM> can include a network interface component or other suitable device to interface with the network <NUM>. In further examples, the communication components <NUM> can include wired communication components, wireless communication components, cellular communication components, near field communication (NFC) components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components, and other communication components to provide communication via other modalities. The devices <NUM> can be another machine or any of a wide variety of peripheral devices (e.g., a peripheral device coupled via a USB).

Moreover, the communication components <NUM> can detect identifiers or include components operable to detect identifiers. For example, the communication components <NUM> can include radio frequency identification (RFID) tag reader components, :N'FC smart tag detection components, optical reader components (e.g., an optical sensor to detect one-dimensional bar codes such as Universal Product Code (UPC) bar code, multi-dimensional bar codes such as Quick Response (QR) code, Aztec code, Data Matrix, Dataglyph, MaxiCode, PDF49, Ultra Code, UCC RSS-2D bar code, and other optical codes), or acoustic detection components (e.g., microphones to identify tagged audio signals). In addition, a variety of information can be derived via the communication components <NUM>, such as location via Internet Protocol (IP) geolocation, location via Wi-Fi® signal triangulation, location via detecting an NFC beacon signal that may indicate a particular location, and so forth. Such identifiers can be used to determine information about one or more of a reference or local impulse response, reference or local environment characteristic, or a listener-specific characteristic.

In various example embodiments, one or more portions of the network <NUM> can be an ad hoc network, an intranet, an extranet, a virtual private network (VPN), a local area network (LAN), a wireless LAN (WLAN), a wide area network (WAN), a wireless WAN (WWAN), a metropolitan area network (MAN), the Internet, a portion of the Internet, a portion of the public switched telephone network (PSTN), a plain old telephone service (POTS) network, a cellular telephone network, a wireless network, a Wi-Fi® network, another type of network, or a combination of two or more such networks. For example, the network <NUM> or a portion of the network <NUM> can include a wireless or cellular network and the coupling <NUM> may be a Code Division Multiple Access (CDMA) connection, a Global System for Mobile communications (GSM) connection, or another type of cellular or wireless coupling. In this example, the coupling <NUM> can implement any of a variety of types of data transfer technology, such as Single Carrier Radio Transmission Technology (1xRTT), Evolution-Data Optimized (EVDO) technology, General Packet Radio Service (GPRS) technology, Enhanced Data rates for GSM Evolution (EDGE) technology, third Generation Partnership Project (3GPP) including <NUM>, fourth generation wireless (<NUM>) networks, Universal Mobile Telecommunications System (UMTS), High Speed Packet Access (HSPA), Worldwide Interoperability for Microwave Access (WiMAX), Long Term Evolution (LTE) standard, others defined by various standard-setting organizations, other long range protocols, or other data transfer technology. In an example, such a wireless communication protocol or network can be configured to transmit headphone audio signals from a centralized processor or machine to a headphone device in use by a listener.

The instructions <NUM> can be transmitted or received over the network <NUM> using a transmission medium via a network interface device (e.g., a network interface component included in the communication components <NUM>) and using any one of a number of well-known transfer protocols (e.g., hypertext transfer protocol (HTTP)). Similarly, the instructions <NUM> can be transmitted or received using a transmission medium via the coupling <NUM> (e.g., a peer-to-peer coupling) to the devices <NUM>. The term "transmission medium" shall be taken to include any intangible medium that is capable of storing, encoding, or carrying the instructions <NUM> for execution by the machine <NUM>, and includes digital or analog communications signals or other intangible media to facilitate communication of such software.

Many variations of the concepts and examples discussed herein will be apparent to those skilled in the relevant arts. For example, depending on the embodiment, certain acts, events, or functions of any of the methods, processes, or algorithms described herein can be performed in a different sequence, can be added, merged, or omitted (such that not all described acts or events are necessary for the practice of the various methods, processes, or algorithms). Moreover, in some embodiments, acts or events can be performed concurrently, such as through multi-threaded processing, interrupt processing, or multiple processors or processor cores or on other parallel architectures, rather than sequentially. In addition, different tasks or processes can be performed by different machines and computing systems that can function together.

The various illustrative logical blocks, modules, methods, and algorithm processes and sequences described in connection with the embodiments disclosed herein can be implemented as electronic hardware, computer software, or combinations of both. To illustrate this interchangeability of hardware and software, various components, blocks, modules, and process actions are, in some instances, described generally in terms of their functionality. The described functionality can thus be implemented in varying ways for a particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of this document. Embodiments of the immersive spatial audio processing and reproduction systems and methods and techniques described herein are operational within numerous types of general purpose or special purpose computing system environments or configurations, such as described above in the discussion of <FIG>.

Conditional language used herein, such as, among others, "can," "might," "may," "e.g.," and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment.

While the above detailed description has shown, described, and pointed out novel features as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the devices or algorithms illustrated can be made without departing from the disclosure. As will be recognized, certain embodiments of the inventions described herein can be embodied within a form that does not provide all of the features and benefits set forth herein, as some features can be used or practiced separately from others.

Claim 1:
A method for providing virtualized audio information, the method comprising:
receiving audio program information (<NUM>) comprising at least N discrete audio signals;
generating, using a first virtualization processor circuit (<NUM>, <NUM>), intermediate virtualized audio information using at least a portion of the received audio program information, the generating including:
applying a first virtualization filter (<NUM>) to M of the N audio signals to provide a first virtualization filter output, the first virtualization filter (<NUM>) comprising a Head-Related Transfer Function, HRTF, filter; and
providing the intermediate virtualized audio information using the first virtualization filter output, wherein the intermediate virtualized audio information comprises J discrete audio signals, wherein J is less than N;
wherein M is less than N, and wherein the providing the intermediate virtualized audio information using the first virtualization filter output includes combining the first virtualization filter output with one or more of the N audio signals that are other than the M audio signals to provide one or more combined audio signals; and
transmitting the intermediate virtualized audio information to a second virtualization processor circuit (<NUM>, <NUM>), wherein the second virtualization processor circuit (<NUM>, <NUM>) is configured to generate further virtualized audio information by applying a different second virtualization filter to one or more of the combined audio signals, the second virtualization filter comprising an HRTF filter;
wherein the second virtualization processor circuit (<NUM>, <NUM>) includes a decorrelator circuit which is configured to apply decorrelation processing to at least one of the combined audio signals prior to applying the second virtualization filter;
wherein N, M, and J are integers.