Preface. 1. Introduction. 2. Signal Processing Essentials. 3. Quantization and Entropy Coding. 4. Linear Prediction in Narrowband and Wideband Coding. 5. Psychoacoustic Principles. 6. Time-Frequency Analysis: Filter Banks and Transforms. 7. Transform Coders. 8. Subband Coders. 9. Sinusoidal Coders. 10. Audio Coding Standards and Algorithms. 11. Lossless Audio Coding and Digital Watermarking. 12. Quality Measures for Perceptual Audio Coding. References. Index.

http://jdsp.engineering.asu.edu/books/cover-page-audio+contents.pdf

Audio Signal Processing and Coding

Networked music performance (NMP) is a potential game changer among Internet applications, as it aims at revolutionizing the traditional concept of musical interaction by enabling remote musicians to interact and perform together through a telecommunication network. Ensuring realistic performance conditions, however, constitutes a significant engineering challenge due to the extremely strict requirements in terms of network delay and audio quality, which are needed to maintain a stable tempo, a satisfying synchronicity between performers and, more generally, a high-quality interaction experience. In this paper, we offer a review of the psycho-perceptual studies conducted in the past decade, aimed at identifying latency tolerance thresholds for synchronous real-time musical performance. We also provide an overview of hardware/software enabling technologies for NMP, with a particular emphasis on system architecture paradigms, networking configurations, and applications to real use cases.

An Overview on Networked Music Performance Technologies

In some embodiments, spatially realistic audio may be provided for a conference call. Voices from participants on the left side of a display, in a conference call, may be directed through audio on the left side of the display at the other conferencing system in the conference call (similarly for voices from the center and right side of the display). In some embodiments, two speakers may be used in the system to create synthesized stereo sound at a location specified by directional information received as side information along with the existing audio channel. The location may be determined by using beamforming with integrated microphones on a camera or speakerphone. In some embodiments, the audio signal and directional information may be sent in the form of a left audio channel and a right audio channel.

Video and audio conferencing system with spatial audio

A method including receiving an input of a character from a virtual keyboard rendered on a display, generating a set of characters that includes the character, and displaying the generated set of characters at a location that is associated with the virtual keyboard and that is on the display. An electronic device including a display having a virtual keyboard rendered thereupon and a processor, the processor being configured to perform the method. Also disclosed is a keyboard, including a plurality of keys, each key corresponding to one or more different characters of a plurality of characters, wherein in response to receiving an input of a character, the keyboard is configured to generate a set of characters that includes the character, and the keyboard is further configured to cause display of the generated set of characters at a location that is associated with the virtual keyboard and that is on the display.

Touchscreen keyboard predictive display and generation of a set of characters

A communication system (e.g., a speakerphone) includes an array of microphones, a speaker, memory and a processor. The processor may perform a virtual broadside scan on the microphone array and analyze the resulting amplitude envelope to identify acoustic source angles. Each of the source angles may be further investigated with a directed beam (e.g., a hybrid superdirective/delay-and-sum beam) to obtain a corresponding beam signal. Each source may be classified as either intelligence or noise based on an analysis of the corresponding beam signal. The processor may design a virtual beam pointed at an intelligence source and having nulls directed at one or more of the noise sources. Thus, the virtual beam may be highly sensitive to the intelligence source and insensitive to the noise sources.

Forming beams with nulls directed at noise sources

An apparatus for generating bandwidth extension output data for an audio signal has a noise floor measurer, a signal energy characterizer and a processor. The audio signal has components in a first frequency band and components in a second frequency band, the bandwidth extension output data are adapted to control a synthesis of the components in the second frequency band. The noise floor measurer measures noise floor data of the second frequency band for a time portion of the audio signal. The signal energy characterizer derives energy distribution data, the energy distribution data characterizing an energy distribution in a spectrum of the time portion of the audio signal. The processor combines the noise floor data and the energy distribution data to obtain the bandwidth extension output data.

An apparatus and a method for generating bandwidth extension output data

Digital audio processing has been revolutionized by perceptual audio coding in the past decade. The main parameter to benchmark different codecs is the audio quality at a certain bit-rate. For many applications, however, delay is another key parameter which varies between only a few and hundreds of milliseconds depending on the algorithmic properties of the codec. Latest research results in low delay audio coding can significantly improve the performance of applications such as communications, digital microphones, and wireless loudspeakers with lip synchronicity to a video signal. This paper describes the delay sources and magnitude of the most common audio codecs and thus provides a guideline for the choice of the most suitable codec for a given application.

/pdf/a-guideline-to-audio-codec-delay-24hlqm39i2.pdf

A Guideline to Audio Codec Delay

An apparatus for generating a bandwidth extended signal from an input signal includes a patch generator and a combiner The input signal is represented for first and second bands by first and second resolution data, respectively, the second resolution being lower than the first The patch generator generates first and second patches from the first band of the input signal according to first and second patching algorithms, respectively A spectral density of the second patch generated using the second patching algorithm is higher than a spectral density of a first patch generated using the first patching algorithm The combiner combines both patches and the first band of the input signal to obtain the bandwidth extended signal The apparatus scales the input signal according to the first and second patching algorithms or scales the first and second patches, so that the bandwidth extended signal fulfills a spectral envelope criterion

Apparatus and Method for Generating a Bandwidth Extended Signal

Implementing MPEG Advanced Audio Coding and Layer-3 Encoders on 32-bit and 16-bit Fixed-point Processors

An apparatus for decoding (100) an encoded audio signal (102). A first decoder (110a) decodes a first portion (104a) in accordance with a first decoding algorithm for a first time portion of the encoded signal (102) to obtain a first decoded signal (114a). A second decoder (110b) decodes a second portion (104b) in accordance with a second decoding algorithm for a second time portion of the encoded signal (102) to obtain a second decoded signal (114b). A BWE module (130) has a controllable crossover frequency (fx) and is configured for performing a bandwidth extension algorithm using the first decoded signal (114a) and BWE parameters (106) for the first portion (104a), and for performing a bandwidth extension algorithm using the second decoded signal (114b) and the bandwidth extension parameters (106) for the second portion (104b). A controller (140) controls the crossover frequency (fx) for the BWE module (130) in accordance with a coding mode information (108).

Marc Gayer

Papers

An apparatus and a method for generating bandwidth extension output data

A Guideline to Audio Codec Delay

Apparatus and Method for Generating a Bandwidth Extended Signal

Implementing MPEG Advanced Audio Coding and Layer-3 Encoders on 32-bit and 16-bit Fixed-point Processors

An apparatus and a method for decoding an encoded audio signal