Dolby Laboratories Licensing Corporation

Thomson Licensing

Johann-Markus Batke

Johannes Boehm

Sven Kordon

Florian Keiler

Alexander Krueger

Peter Jax

Alexander Krüger

Mark R P Thomas

Holger Kropp

Alexander Kruger

Soundfield signals such as e.g. Ambisonics carry a representation of a desired sound field. The Ambisonics format is based on spherical harmonic decomposition of the soundfield, and Higher Order Ambisonics (HOA) uses spherical harmonics of at least 2order. However, commonly used loudspeaker setups are irregular and lead to problems in decoder design. A method for improved decoding an audio soundfield representation for audio playback comprises calculating a panning function (W) using a geometrical method based on the positions of a plurality of loudspeakers and a plurality of source directions, calculating a mode matrix (Ξ) from the loudspeaker positions, calculating a pseudo-inverse mode matrix (Ξ) and decoding the audio soundfield representation. The decoding is based on a decode matrix (D) that is obtained from the panning function (W) and the pseudo-inverse mode matrix (Ξ).

Method and device for decoding an audio soundfield representation

A method and apparatus for decompressing a Higher Order Ambisonics (HOA) signal representation is disclosed. The apparatus includes an input interface that receives an encoded directional signal and an encoded ambient signal and an audio decoder that perceptually decodes the encoded directional signal and encoded ambient signal to produce a decoded directional signal and a decoded ambient signal, respectively. The apparatus further includes an extractor for obtaining side information related to the directional signal and an inverse transformer for converting the decoded ambient signal from a spatial domain to an HOA domain representation of the ambient signal. The apparatus also includes a synthesizer for recomposing a Higher Order Ambisonics (HOA) signal from the HOA domain representation of the ambient signal and the decoded directional signal. The side information includes a direction of the directional signal selected from a set of uniformly spaced directions.

Method and apparatus for compressing and decompressing a higher order ambisonics signal representation

Method and apparatus for compressing and decompressing a higher order Ambisonics signal representation

Method and apparatus for compressing and decompressing a Higher Order Ambisonics signal representation

Soundfield signals such as e.g. Ambisonics carry a representation of a desired sound field. The Ambisonics format is based on spherical harmonic decomposition of the soundfield, and Higher Order Ambisonics (HOA) uses spherical harmonics of at least 2order. However, commonly used loudspeaker setups are irregular and lead to problems in decoder design. A method for improved decoding an audio soundfield representation for audio playback comprises calculating a panning function (W) using a geometrical method based on the positions of a plurality of loudspeakers and a plurality of source directions, calculating a mode matrix (&#x39e;) from the loudspeaker positions, calculating a pseudo-inverse mode matrix (&#x39e;) and decoding the audio soundfield representation. The decoding is based on a decode matrix (D) that is obtained from the panning function (W) and the pseudo-inverse mode matrix (&#x39e;).

Soundfield signals such as e.g. Ambisonics carry a representation of a desired sound field. Methods and apparatus for improved decoding an audio soundfield representation for audio playback comprise receiving, by a processor configured to decode the audio soundfield representation, the audio soundfield representation, receiving, by the processor, a decode matrix for decoding the audio soundfield representation to determine a decoded audio signal. The decode matrix is based on an inverse of a mode matrix, and the coefficients of the mode matrix relate to information for a panning based on positions of loudspeakers over a unit sphere. The mode matrix is further based on an order N. The decoded audio signal is determined based on a multiplication of the decode matrix and the audio soundfield representation.

Spherical microphone arrays capture a three-dimensional sound field (P(&#x3a9;, t)) for generating an Ambisonics representation (A(t)), where the pressure distribution on the surface of the sphere is sampled by the capsules of the array. The impact of the microphones on the captured sound field is removed using the inverse microphone transfer function. The equalization of the transfer function of the microphone array is a big problem because the reciprocal of the transfer function causes high gains for small values in the transfer function and these small values are affected by transducer noise. The invention minimizes that noise by using a Wiener filter processing in the frequency domain, which processing is automatically controlled per wave number by the signal-to-noise ratio of the microphone array.

Method and apparatus for processing signals of a spherical microphone array on a rigid sphere used for generating an ambisonics representation of the sound field

Method and device for decoding an audio soundfield representation for audio playback

Spherical microphone arrays capture a three-dimensional sound field (P(&#x3a9;t)) for generating an Ambisonics representation (A(t)), where the pressure distribution on the surface of the sphere is sampled by the capsules of the array. The impact of the microphones on the captured sound field is removed using the inverse microphone transfer function. The equalization of the transfer function of the microphone array is a big problem because the reciprocal of the transfer function causes high gains for small values in the transfer function and these small values are affected by transducer noise. The present principles minimize that noise by using a Wiener filter processing () in the frequency domain, which processing is automatically controlled () per wave number by the signal-to-noise ratio of the microphone array.

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Hannover, Germany

Johann-Markus Batke