Chris Dunn’s research while affiliated with KWS UK Ltd and other places

... Two methods exist for HRTF measurement: deconvolution approaches and systems based on adaptive filters [49]. The most used methods are the ones based on deconvolution, and they can be categorised depending on the type of signal given as input, i.e., pseudo random sequences [47,[50][51][52][53][54][55][56][57][58] or sweep signals [59][60][61][62][63]. Pseudo random sequences embrace maximum length sequences (MLSs) [51][52][53][54][55], inverse repeated sequences (IRSs) [56,57], and Golay codes [58]. The sweep signals can consider multiple exponential/logarithmic sweep [64,65] and multi-sine approaches [66]. ...

Reference:

A Review on Head-Related Transfer Function Generation for Spatial Audio

... The basic idea of adaptive ΔΣMs is to adapt the amplitude of the ΔΣ-sequence to the amplitude of the input signal such that the SNR roughly remains constant— at least within a specified range of input amplitudes. Various different types of adaptive ΔΣMs can be found in literature, for example,3456789. Adaptation algorithms based on " syllabic adaptation " [3, 4, 6, 7] are controlled by short time properties , for example, by the peak amplitude, within so-called " stationary periods " (typically between 10–30 milliseconds for speech, and about 5 milliseconds for music [4]) of the input. ...

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Adaptive Delta-Sigma Modulation for Enhanced Input Dynamic Range

... One approach for exploiting efficiently spatial correlations for compression is to decompose the image into a set of binary layers (bit-planes), and then compress these layers by a binary image compression technique [2], [3], [4], [5]. The decompression is an inverse process of the compression, where the compressed file is decompressed into a set of layers which are then combined back into the gray-scale image. ...

Reference:

A Low-complexity Lossless Image Compression for Small Spacescrafts’ On-board Computers

... Since some of the measurement techniques require the generation of a known jitter signal, the paper describes the design and operation of a simple jitter modulator. It has been shown that cable losses within the AES3 digital audio interface interact with the modulated data to introduce timing jitter in the transitions of the modulated part of the signal [3,4]. This mechanism has been shown to form a significant contribution to overall jitter in systems with cable runs of more than a few metres. ...

Reference:

The Diagnosis and solution of jitter-related problems in digital audio systems

... Bit-plane methods typically offer finer granularity and lower computational complexity than standard multilayer approaches, but their overall RD performance is relatively weaker, as demonstrated in Section VIII. Current bit-plane based scalable coding methods for audio, such as BSAC [25], EZK [26], and ESC [27], use variants of the basic hierarchical partitioning technique, a method originally developed for image coding [28], [29]. ...

Reference:

Efficient bit-rate scalability for weighted squared error optimization in audio coding

... In the proposed scheme, in addition to band-wise weighting data (i.e. scale factors, [8] ) the scalefactor-band wise values of the l 1 norm of the spectral envelopes are calculated and transmitted as side information. This side information is followed by a fully embedded bitstream which is created by the set partitioning in hierarchical trees (SPIHT) algorithm and describes the actual waveform of the signal. ...

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Fine-grain scalable audio coding based on envelope restoration and the SPIHT algorithm

... The Quality trial focuses on audio quality evaluation of a castanet recording, from [22]. The audio was low-passed filtered at various frequencies to create different levels of quality. ...

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Investigation into the effects of subjective test interface choice on the validity of results

... Several attempts have been made to modify the standard recursion (1.6) to break up periodic output without sacrificing accuracy of the resulting reconstruction. One suggested approach is to apply dither, or white noise, to the input f n before implementing the recursion [2]. Another alternative, not necessarily mutually exclusive to dithering, is to break periodicities by incorporating expansion into the recursion (1.6), considering instead q n = Q(u n−1 + γv n−1 ) ...

Reference:

Stability for second-order chaotic sigma delta quantization

... The spectral masking output current is converted to a digital signal (Figures 5 and 6) through a current-to-frequency (I2F) digital oscillation (Figure 2) similar to an integrateand-fire neuron [19] or Σ-∆ modulator. Some digital MP3 implementations take advantage of the shaped noise floor of a Σ-∆ converter as part of their psychoacoustic model [33]. Integrating the current on the input capacitor (C L2 ) increases the capacitor voltage until it reaches a threshold V re f , where the comparator turns on an additional discharge path (through a T-gate switch) to rapidly discharge the input capacitor. ...

Reference:

An Analog MP3 Compression Psychoacoustic Model Implemented on a Field-Programmable Analog Array

... The effect of dither on IBN power bumps is also analyzed to find out whether it can help to reduce them. Dither injects a pseudorandom sequence at the quantizer input that helps to decorrelate the quantization error and the input signal; it has been widely used to attenuate idle tones [12][13][14]. Dither has been implemented with a thirteenth-order Linear Feedback Shift Register (LFSR). The signal activity at the quantizer input is increased and the probability of using more than two levels is increased. ...

Reference:

An Analysis of Noise in Multi-Bit ΣΔ Modulators with Low-Frequency Input Signals