Structured vector quantization using linear transforms

This paper presents novel structured vector quantization (VQ) techniques characterized by the use of linear transformations for the input VQ. The first technique is called the affine transformations VQ, in which the quantized vector is formed by adding the transformed outputs of a multistage codebook rather than just adding the outputs of the stages as in regular multistage vector quantization (MSVQ). The name of the VQ technique comes from the fact that in the two-stage case, the quantized vector is obtained as the result of an affine transformation. This technique can be viewed as a generalized form of MSVQ. If the transformations are constrained to be the identity transformation, this technique becomes identical to the regular MSVQ. The transformations in the introduced technique are selected from a family of linear transformations, represented by a codebook of matrices. In order to I reduce the memory required for storing the matrices, the paper discusses a second technique called scaled rotation matrices VQ, where matrices are constrained to be scaled rotation matrices. Since rotation matrices can be stored by just storing the corresponding rotation angles, this approach enables efficient storage of linear transforms. The design algorithms are based on joint optimization of the linear transformation and the stage codebooks. Experimental results based on speech spectrum quantization show that the proposed VQ techniques outperform the MSVQ of the same bit rate.     

Lattice low-delay vector excitation coding of speech at 8-16 kb/s

Lattice low-delay vector excitation coding (LLD-VXC) is a speech coding system based on analysis-by-synthesis excitation coding and backward adaptation of the synthesis filter. The introduction of a lattice filter as a (high order) short-term predictor has significant advantages, such as fast tracking of speech signal nonstationarities, simple stability verification, and uniform distribution of the computational load. The objective of this paper is to present a Lattice LD-VXC (LLD-VXC) codec-and experimental results obtained at rates of 8, 9.6, and 16 kb/s. A sign algorithm for lattice filter adaptation is introduced in order to reduce computational complexity. An LLD-VXC codec with a 20th-order lattice predictor, a 10th-order lattice weighting filter, and a backward pitch predictor achieved toll quality at 16 kb/s and good communications quality at 8-9.6 kb/s with a delay of less than 2 ms and reasonable complexity     

On adaptive vector transform quantization for speech coding

Adaptive vector transform quantization (AVTQ) as a coding system is discussed. The optimal bit assignment is derived based on vector quantization asymptotic theory for different PDFs (probability density functions) of the transform coefficients. Strategies for shaping the quantization noise spectrum and for adapting the bit assignment to the changes in the speech statistics are discussed. A good estimate of the efficiency of any coding system is given by the system coding gain over scalar PCM (pulse code modulation). Based on the optimal bit allocation, the coding gain of the vector transform quantization (VTQ) system operating on a stationary input signal is derived. The VTQ coding gain demonstrates a significant advantage of vector quantization over scalar quantization within the framework of transform coding. System simulation results are presented for a first-order Gauss-Markov process and for typical speech waveforms. The results of fixed and adaptive systems are compared for speech input. Also, the AVTQ results are compared to known scalar speech coding systems     

Big Five predictors of behavior and perceptions in initial dyadic interactions: Personality similarity helps extraverts and introverts, but hurts “disagreeables”.

The authors used the unstructured dyadic interaction paradigm to examine the effects of gender and the Big Five personality traits on dyad members’ behaviors and perceptions in 87 initial, unstructured interactions. Most of the significant Big Five effects (84%) were associated with the traits of Extraversion and Agreeableness. There were several significant actor and partner effects for both of these traits. However, the most interesting and novel effects took the form of significant Actor × Partner interactions. Personality similarity resulted in relatively good initial interactions for dyads composed of 2 extraverts or 2 introverts, when compared with dissimilar (extravert–introvert) pairs. However, personality similarity resulted in uniquely poor initial interactions for dyads composed of 2 “disagreeables.” In summary, the Big Five traits predict behavior and perceptions in initial dyadic interactions, not just in the form of actor and partner “main effects” but also in the form of Actor × Partner interactions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Low-delay vector excitation coding of speech at 16 kb/s

The need for a 16-kb/s speech coding algorithm that has very low coding delay while achieving essentially the same high quality as the 32-kb/s adaptive differential pulse code modulation (ADPCM) standard G.721 is addressed. The authors describe low-delay vector excitation coding (LD-VXC), a new coding algorithm which provides high quality with less than 2 ms of coding delay and is robust to transmission errors. The algorithm combines techniques such as vector quantization, analysis-by-synthesis, and perceptual weighting together with backward adaptive linear predictive encoding, and uses a novel long-term predictor employing backward adaptive pitch tracking. Perceptually based nose shaping and postfiltering contribute to the masking of audible quantization noise