Motorola Mobility LLC

Motorola Corporation

Google Inc.

Google Technology Holdings LLC

Jonathan A Gibbs

James Patrick Ashley

Udar Mittal

Holly Francois

Richard C Lucas

Nicholas William Whinnett

William Neil Robinson

Anthony P Van Den Heuvel

Andrew John Aftelak

James P Ashley

Mark A Jasiuk

Michael Joseph McLaughlin

David Nigel Freeman

Shaun Richard Fenton

William Robinson

David John Pearce

Antony John Wray

Dragan Boscovic

Timor Kadir

Tiong Tan Boon

Christopher Philip Johnson

Dominic Chan

Anthony Van Den Heuvel

Halil Fikretler

Holly L Francois

An encoding apparatus comprises a frame processor () which receives a multi channel audio signal comprising at least a first audio signal from a first microphone () and a second audio signal from a second microphone (). An ITD processorthen determines an inter time difference between the first audio signal and the second audio signal and a set of delays () generates a compensated multi channel audio signal from the multi channel audio signal by delaying at least one of the first and second audio signals in response to the inter time difference signal. A combiner () then generates a mono signal by combining channels of the compensated multi channel audio signal and a mono signal encoder () encodes the mono signal. The inter time difference may specifically be determined by an algorithm based on determining cross correlations between the first and second audio signals.

Apparatus and method for encoding a multi-channel audio signal

An apparatus receives an input encoded audio data signal comprising a base layer and at least one enhancement layer. A reference unit () generates reference audio data corresponding to audio data of a reference set of layers. A layer unit () divides the layers of the input signal into a first subset and a second subset. A sample unit () generates sample audio data corresponding to the audio data of the first subset. A comparison unit () generates a difference measure by comparing the sample audio data to the reference audio data based on a perceptual model. An output unit () then determines if the difference measure meets a similarity criterion and generates an output signal without audio data from a layer of the second subset if the similarity criterion is met and including the audio data of the layer otherwise. The invention may provide reduced data rates without an unacceptable degradation of quality.

Apparatus and method for generating an output audio data signal

A hybrid speech encoder detects changes from music-like sounds to speech-like sounds. When the encoder detects music-like sounds (e.g., music), it operates in a first mode, in which it employs a frequency domain coder. When the encoder detects speech-like sounds (e.g., human speech), it operates in a second mode, and employs a time domain or waveform coder. When a switch occurs, the encoder backfills a gap in the signal with a portion of the signal occurring after the gap.

Method and apparatus for encoding an audio signal

A method and apparatus for encoding a signal is provided herein. During operation a wideband signal that is to be encoded enters a filter bank. A highband signal and a lowband signal are output from the filter bank. Each signal is separately encoded. During the production of the highband signal, a downmixing operation is implemented after preprocessing, and prior to decimating. The downmixing operation greatly reduces system complexity. In fact, it will be observed that the highest sample rate in the prior-art implementation is 64 kHz whereas the sample rate in the system described above remains at 32 kHz or below. This represents a significant complexity saving, as do the reduced number of processing blocks.

Method and apparatus for encoding a wideband speech signal utilizing downmixing of a highband component

An encoder and decoder for processing an audio signal including generic audio and speech frames are provided herein. During operation, two encoders are utilized by the speech coder, and two decoders are utilized by the speech decoder. The two encoders and decoders are utilized to process speech and non-speech (generic audio) respectively. During a transition between generic audio and speech, parameters that are needed by the speech decoder for decoding frame of speech are generated by processing the preceding generic audio (non-speech) frame for the necessary parameters. Because necessary parameters are obtained by the speech coder/decoder, the discontinuities associated with prior-art techniques are reduced when transitioning between generic audio frames and speech frames.

Method and apparatus for audio coding and decoding

A method for decoding an audio signal in a decoder having a CELP-based decoder element including a fixed codebook component, at least one pitch period value, and a first decoder output, wherein a bandwidth of the audio signal extends beyond a bandwidth of the CELP-based decoder element. The method includes obtaining an up-sampled fixed codebook signal by up-sampling the fixed codebook component to a higher sample rate, obtaining an up-sampled excitation signal based on the up-sampled fixed codebook signal and an up-sampled pitch period value, and obtaining a composite output signal based on the up-sampled excitation signal and an output signal of the CELP-based decoder element, wherein the composite output signal includes a bandwidth portion that extends beyond a bandwidth of the CELP-based decoder element.

Audio signal bandwidth extension in CELP-based speech coder

A method for decoding an audio signal having a bandwidth that extends beyond a bandwidth of a CELP excitation signal in an audio decoder including a CELP-based decoder element. The method includes obtaining a second excitation signal having an audio bandwidth extending beyond the audio bandwidth of the CELP excitation signal, obtaining a set of signals by filtering the second excitation signal with a set of bandpass filters, scaling the set of signals using a set of energy-based parameters, and obtaining a composite output signal by combining the scaled set of signals with a signal based on the audio signal decoded by the CELP-based decoder element.

Apparatus () for encoding at least one parameter associated with a signal source for transmission over k frames to a decoder comprises a processor () which is configured in operation to assign a predetermined bit pattern to n bits associated with the at least one parameter of a first frame of k frames and set the n bits associated with the at least one parameter of each of k&#x2212;1 subsequent frames to values, such that the values of the n bits of the k&#x2212;1 subsequent frames represent the at least one parameter. The predetermined bit pattern indicates a start of the at least one parameter.

Apparatus and method for encoding at least one parameter associated with a signal source

In a selective signal encoder, an input signal is first encoded using a core layer encoder to produce a core layer encoded signal. The core layer encoded signal is decoded to produce a reconstructed signal and an error signal is generated as the difference between the reconstructed signal and the input signal. The reconstructed signal is compared to the input signal. One of two or more enhancement layer encoders selected dependent upon the comparison and used to encode the error signal. The core layer encoded signal, the enhancement layer encoded signal and the selection indicator are output to the channel (for transmission or storage, for example).

Method and apparatus for selective signal coding based on core encoder performance

An encoding apparatus comprises a frame processor () which receives a multi channel audio signal comprising at least a first audio signal from a first microphone () and a second audio signal from a second microphone (). An ITD processor 107 then determines an inter time difference between the first audio signal and the second audio signal and a set of delays () generates a compensated multi channel audio signal from the multi channel audio signal by delaying at least one of the first and second audio signals in response to the inter time difference signal. A combiner () then generates a mono signal by combining channels of the compensated multi channel audio signal and a mono signal encoder () encodes the mono signal. The inter time difference may specifically be determined by an algorithm based on determining cross correlations between the first and second audio signals.

A method for estimating a parameter for low bit rate stereo transmission that includes deriving estimate of any time delay between left and right audio channels in a multi-channel signal from a time delay subsystem. A cross-correlation between the left and right audio channels in the time delay subsystem is employed. Thereafter a normalized cross-correlation within an inter-channel intensity difference (IID) processor is employed before deriving estimate of panning gains for the left and right audio channels from the IID processor.

Method and apparatus for estimating a parameter for low bit rate stereo transmission

A method for processing an audio signal including classifying an input frame as either a speech frame or a generic audio frame, producing an encoded bitstream and a corresponding processed frame based on the input frame, producing an enhancement layer encoded bitstream based on a difference between the input frame and the processed frame, and multiplexing the enhancement layer encoded bitstream, a codeword, and either a speech encoded bitstream or a generic audio encoded bitstream into a combined bitstream based on whether the codeword indicates that the input frame is classified as a speech frame or as a generic audio frame, wherein the encoded bitstream is either a speech encoded bitstream or a generic audio encoded bitstream.

Embedded speech and audio coding using a switchable model core

A method for decoding audio frames includes producing a first frame of coded audio samples, producing at least a portion of a second frame of coded audio samples, generating audio gap filler samples based on parameters representative of a weighted segment of the first frame of coded audio samples or a weighted segment of the portion of the second frame of coded audio samples, and forming a sequence including the audio gap filler samples and the portion of the second frame of coded audio samples.

Decoder for audio signal including generic audio and speech frames

A method for encoding audio frames by producing a first frame of coded audio samples by coding a first audio frame in a sequence of frames, producing at least a portion of a second frame of coded audio samples by coding at least a portion of a second audio frame in the sequence of frames, and producing parameters for generating audio gap filler samples, wherein the parameters are representative of either a weighted segment of the first frame of coded audio samples or a weighted segment of the portion of the second frame of coded audio samples.

Encoder for audio signal including generic audio and speech frames

During operation an input signal to be coded is received and coded to produce a coded audio signal. The coded audio signal is then scaled with a plurality of gain values to produce a plurality of scaled coded audio signals, each having an associated gain value and a plurality of error values are determined existing between the input signal and each of the plurality of scaled coded audio signals. A gain value is then chosen that is associated with a scaled coded audio signal resulting in a low error value existing between the input signal and the scaled coded audio signal. Finally, the low error value is transmitted along with the gain value as part of an enhancement layer to the coded audio signal.

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Winchester, United Kingdom

Jonathan A Gibbs