VQ Technique Research Articles

Robust speaker verification in band-localized noise conditions

This research paper presents a robust method for speaker verification in noisy environments. The noise is assumed to contaminate certain parts of the voice’s frequency spectrum. Therefore, the verification method is based on splitting the noisy speech into subsidiary bands then using a threshold to sense the existence of noise in a specific part of the spectrum, hence activating an adaptive filter in that part to track changes in noise’s characteristics and remove it. The decomposition is achieved using low complexity quadrature mirror filters QMF in three levels thus achieving four bands in a non-uniform that resembles human hearing perceptual. Speaker recognition is based on vector quantization VQ or template matching technique. Features are extracted from speaker’s voice using the normalized power in a similar way to the Mel-frequency cepstral coefficients. The performance of the proposed system is evaluated using 60 speakers subjected to five levels of signal to noise ratio SNR using total success rate TSR, false acceptance rate FAR, false rejection rate FRR and equal error rate. The proposed method showed higher recognition accuracy than existing methods in severe noise conditions.

Speaker Identification System in Controlled Environment using MFCC and VQ Technique

Speaker Identification System in Controlled Environment using MFCC and VQ Technique

Multiresolution image VQ compression by color codebook reordering

In this paper, a method to reach multiresolution VQ is proposed. A reordering process of color vectors from the codebook is performed. This yields to obtain an index image very close to the initial luminance image that can be obtained from any color image, but at a lower resolution. That way, the VQ technique can be applied once again on this new index image. In other words, a hierarchical and multiresolution VQ is defined. At each stage of the VQ compressed image, one is able to reconstruct it using the initial color codebook and the index one.A comparison of the proposed method and classical Hierarchical VQ (HVQ) scheme at different compression levels is performed to judge the performance and the robustness of the hybrid method. B oth objective and subjective measures are used.This work is a preliminary work to compress high dimension images at different levels.

Image vector quantization with variable dimension blocks and edge preserving cost function

This paper proposes a vector quantization scheme that uses variable vector dimensions and improves the perceived quality of the reconstructed images by using an edge based cost function. The cost function used for encoding is modified to take into account the number of edge pixels in a particular encoding block. For a better subjective quality, the product of the fraction of the edge pixels and the fraction of the non-edge pixels should be minimized. This is included in the additive cost function of VQ and minimized as an unconstrained problem. This edge based VQ technique reduces edge artifacts like jagging, ringing and also VQ distortions that happen near object contours, thus improving the overall subjective quality of the reconstructed image.

SIMULTANEOUS MALONE ANTEGRADE CONTINENT ENEMA AND MITROFANOFF PRINCIPLE USING THE DIVIDED APPENDIX: REPORT OF A NEW TECHNIQUE FOR PREVENTION OF STOMA COMPLICATIONS

We determine the results and complications of continent urinary diversion and simultaneous Malone antegrade continent enema (MACE) and the Mitrofanoff principle using the divided appendix, and report on the VQQ and VQ technique for prevention of complications at the stoma level. Between June 1995 and June 1999, 40 patients 4 to 22 years old (mean age 9.5) underwent Mitrofanoff procedures in conjunction with the MACE and augmentation cystoplasty as primary (5) or salvage (35) therapy. Of the patients 35 had neuropathic bladder, and 5 had bladder and bowel dysfunction without detectable neurological abnormalities. All patients had an antireflux Mitrofanoff channel constructed using distal part of the appendix with its divided mesothelium. The proximal half of the appendix was preserved as a modified MACE. Average length of appendix was 10.3 cm. (range 9 to 15) and no correlation was found between the length of appendix and age of child. The stoma construction was performed as 2 different techniques. The 2 appendix stomas were initially anastomosed with 2 separate triangular posterior V shape skin flaps on the right lower abdominal wall. Both appendix mucosae were completely buried with a single or double quadrilateral skin flap (VQQ and VQ technique). All patients are continent day and night without diapers. Mean followup was 22 months (range 8 to 48) and the overall incidence of complications was 7.5%. Mitrofanoff stomal stenosis due to catheter false passage occurred postoperatively in 1 case, gas leakage from the MACE in 1 and partial mucosal prolapse in 1. The MACE and Mitrofanoff principle have proved invaluable for the treatment of children with urinary and fecal incontinence. The divided appendix with 2 separate mesotheliums is an ideal channel for simultaneous Mitrofanoff and MACE when the appendix length is 9 cm. or more with a suitable branching mesothelium. When the appendix is short we prefer to use it as the Mitrofanoff and create a pediculed tube flap from the cecum for the MACE. All patients with a short appendix or history of appendectomy operated on by different techniques, such as the Monti procedure, Casale technique, cecal flap or ureteral Mitrofanoff, were excluded from our study. Most of the minor complications are preventable by meticulous technique. The VQQ and VQ stomas have the lowest incidence of complications and produce the most satisfactory cosmetic appearance.

Simultaneous Malone antegrade continent enema and Mitrofanoff principle using the divided appendix: report of a new technique for prevention of stoma complications.

We determine the results and complications of continent urinary diversion and simultaneous Malone antegrade continent enema (MACE) and the Mitrofanoff principle using the divided appendix, and report on the VQQ and VQ technique for prevention of complications at the stoma level. Between June 1995 and June 1999, 40 patients 4 to 22 years old (mean age 9.5) underwent Mitrofanoff procedures in conjunction with the MACE and augmentation cystoplasty as primary (5) or salvage (35) therapy. Of the patients 35 had neuropathic bladder, and 5 had bladder and bowel dysfunction without detectable neurological abnormalities. All patients had an antireflux Mitrofanoff channel constructed using distal part of the appendix with its divided mesothelium. The proximal half of the appendix was preserved as a modified MACE. Average length of appendix was 10.3 cm. (range 9 to 15) and no correlation was found between the length of appendix and age of child. The stoma construction was performed as 2 different techniques. The 2 appendix stomas were initially anastomosed with 2 separate triangular posterior V shape skin flaps on the right lower abdominal wall. Both appendix mucosae were completely buried with a single or double quadrilateral skin flap (VQQ and VQ technique). All patients are continent day and night without diapers. Mean followup was 22 months (range 8 to 48) and the overall incidence of complications was 7.5%. Mitrofanoff stomal stenosis due to catheter false passage occurred postoperatively in 1 case, gas leakage from the MACE in 1 and partial mucosal prolapse in 1. The MACE and Mitrofanoff principle have proved invaluable for the treatment of children with urinary and fecal incontinence. The divided appendix with 2 separate mesotheliums is an ideal channel for simultaneous Mitrofanoff and MACE when the appendix length is 9 cm. or more with a suitable branching mesothelium. When the appendix is short we prefer to use it as the Mitrofanoff and create a pediculed tube flap from the cecum for the MACE. All patients with a short appendix or history of appendectomy operated on by different techniques, such as the Monti procedure, Casale technique, cecal flap or ureteral Mitrofanoff, were excluded from our study. Most of the minor complications are preventable by meticulous technique. The VQQ and VQ stomas have the lowest incidence of complications and produce the most satisfactory cosmetic appearance.

Progressive Image Transmission Using LOT with Two-Channel Conjugate VQ

A progressive image transmission (PIT) scheme based on the classified two-channel conjugate VQ (TCCVQ) technique in the lapped orthogonal transform (LOT) domain is proposed. Conventional block transform coding of images using DCT produces in general undesirable block-artifacts at low bit rates. In this paper, image blocks are transformed using the LOT and classified into four classes based on their structural properties and further subdivided adaptively into subvectors depending on the LOT coefficient statistics to improve the reconstructed image quality by adaptive bit allocation. The subvectors are quantized using the two-channel conjugate VQ technique which has less computational complexity and less storage memory, and is more robust against channel errors. The vector quantized subvectors are transmitted and decoded in stages so that an image is progressively reconstructed, i.e., initially a crude version followed by quality build up in successive stages as the occasion demands in interactive visual communications. Coding tests using computer simulations show that the LOT/TCCVQ-based PIT of images is an effective coding scheme. The results are also compared with those obtained using conventional classified VQ in both the DCT and LOT domains.

Image compression using nonlinear pyramid vector quantization

In this paper, we present a new image compression scheme that exploits the VQ technique in a hierarchical nonlinear pyramid structure. We use multistage median filters (MMF) to build the image pyramids. Image pyramids generated by MMF show a better details preservation than the ones generated by Burt's kernel. It is shown that MMF effectively decorrelates the difference pyramids, resulting in smaller first order entropy. Our simulations on natural images show that NPVQ yields a higher SNR as well as better image quality, in comparison with LPVQ. The NPVQ scheme is also appropriate for progressive image transmission.

Spectral coding by LSP frequencies—scalar and segmented VQ-methods

Line spectrum pairs (LSP) is one interesting way of representing the filter parameters of a linear production model. In particular, LSPs have been used for quantisation, i.e. for the spectral coding problem of speech coding. The concept of close-to-optimal search strategies, as well as optimal quantiser design, is discussed for the case of LSP-based quantisation. Previous scalar approaches are generalised to a vectorial treatment by carefully selecting a VQ technique that can provide robust results with low complexity. Simulation results are presented both for the scalar and for the vectorial case, showing that a two-dimensional VQ approach can provide substantial bit savings in realistic cases.

Image coding based on two-channel conjugate VQ

Two-channel conjugate VQ (TCCVQ) has been recently proposed for speech coding. Compared to ordinary VQ, two-channel conjugate VQ requires less computational complexcity and less storage (memory) and is more robust against channel errors. This technique is now extended to image coding. The emphasis in this paper is on the usefulness of the TCCVQ when it is applied to image coding or is combined with a conventional image coding technique. Initial investigation confirms these advantages of two-channel conjugate VQ. For a noise-free channel the performances of both techniques are similar. However, when channel noise is injected, for the same bit rate, images reconstructed based on two-channel conjugate VQ are subjectively more pleasing (have less visible distortion) than those based on ordinary VQ. Both VQ techniques are also applied to a well-known separating mean VQ and are tested for robustness against channel errors. Computer simulations demonstrate the success of the two-channel conjugate VQ technique for image data compression at various bit rates.