• Journal of the Institute of Electronics Engineers of Korea SP
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• v.49 no.1
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• pp.11-18
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• 2012

In this paper, an entropy constrained vector quantizer for high bit-rates is proposed. The sample-adaptive product quantizer (SAPQ), which is based on the product codebooks, is employed, and a design algorithm for the entropy constrained sample adaptive product quantizer (ECSAPQ) is proposed. The performance of the proposed ECSAPQ is better than the case of the entropy constrained vector quantizer by 0.5dB. It is also shown that the ECSAPQ distortion curve, which is based on the scalar quantizer, is lower than the high-rate theoretical curve of the entropy constrained scalar quantizer, where the theoretical curve have 1.53dB difference from Shannon's lower bound.

• The Journal of the Acoustical Society of Korea
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• v.23 no.4
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• pp.333-339
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• 2004

This Paper proposes the vector quantizer-pyramid vector quantizer(VQ-PVQ) structure. Also both predictive structure and safety-net concept are combined into the VQ-PVQ to quantize the IPC parameter of wideband speech codec. The Performance is compared to the LPC vector quantizer used in the AMR-WB(ITU-T G.722.2). demonstrating reduction in both spectral distortion and encoding memory.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.2
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• pp.333-339
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• 1996

In this paper, an effiicent quatization method of line spectrum pairs(LSP) with cascaded structure of vector quantizer and scalar quantizer is proposed. First, input LSP parameters is vector-quantized using a codebook with a moderate number of entries. In the second stage of quantization, the components of residual vector are individution improve the quantizer by the scalar quantizer. The utilization of ordering property and the inclusion of interframe prediction improve the quantizer performance and remove the stability check routine. The new vector-scalar cascaded quantizer using 27 bits/frame shows a transparent quality that an average specytural distortion is 1 dB and the frame proportion with above 2 dB spectral distion is less than 2%.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.40 no.4
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• pp.286-291
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• 2003

In this Paper, we designed an LSP(Line Spectral Pairs) parameter quantizer with cascaded structure of vector quantizer and scalar quantizer for the wideband speech coder. We have chosen the 16th-order of the LP coefficients. These coefficients are then transformed into the LSP parameters which have the excellent properties for quantization and easy stability checking condition of synthesis filter. In the first stage of quantization, input LSP parameters are split-vector-quantized using two 8-th order codebooks. In the second stage, the components of residual vector are individually quantized by the scalar quantizer utilizing the ordering property of LSP parameters. The designed adaptive VQ-SQ quantizer using 35 bits/frame shows the wideband transparency that the average spectral distortion should be less than 1.6 ㏈ and less than 4% of the frames should have SD above 3 ㏈. The simulation results show that the designed quantizer provides a 2-3 bits/frame saving over the typical vector-scalar quantizer.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12B
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• pp.2382-2390
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• 1999

In this paper, we employed a new quantization scheme called sample-adaptive product quantizer (SAPQ) to quantize image data based on the differential pulse code modulation (DPCM) coder, which has fixed length outputs and high bit rates. In order to improve the performance of traditional DPCM coders, the scalar quantizer should be replaced by the vector quantizer (VQ). As the bit rate increases, it will be nearly impossible to implement a conventional VQ or modified VQ, such as the tree-structured VQ, even if the modified VQ can significantly reduce the encoding complexity. SAPQ has a form of the feed-forward adaptive scalar quantizer having a short adaptation period. However, since SAPQ is a structurally constrained VQ, SAPQ can achieve VQ-level performance with a low encoding complexity. Since SAPQ has a scalar quantizer structure, by using the traditional scalar value predictors, we can easily apply SAPQ to DPCM coders. For synthetic data and real images, by employing SAPQ as the quantizer part of DPCM coders, we obtained a 2~3 dB improvement over the DPCM coders, which are based on the Lloyd-Max scalar quantizers, for data rates above 4 b/point.

• Proceedings of the KIEE Conference
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• 1996.07b
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• pp.1362-1364
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• 1996

In this paper a Dear lossless compression of medical images with vector quantizer is proposed. In order to apply the vector quantizer to medical images, the peak error in the reconstructed image is reduced down to 1. Simulation results show that the proposed coding scheme provides better performance with a PSNR improvement compared to the conventional JPEG standard.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.127-136
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• 1998

This paper proposes a new MVQMultistage Vector Quantizer) using a hybrid structure. While in a conventional MVQ, the quantizers of all stages perform the encoding procedure for input signals, we introduce a quantizer that performs selectively. The proposed quantizer with a hybrid structure is composed of a FSVQ(Finite-State Vector Quantizer) for the first stage and a ordinary VQ(Vector Quantizer) for the second stage. A input block is firstly encoded by the FSVQ of the first stage. If the Euclidean distortion measure between original signals and the codevector selected from the state codebook of the FSVQ is less than a prespecified value, only the FSVQ is used for image coding. Otherwise, both the FSVQ of the first stage and the ordinary VQ of the second stage are used for image coding. While the conventional MVQ has an advantage that can achieve low encoding complexity in comparison to the ordinary VQ, but has a disadvantage that is suboptimal with respect to the performance measure and can not achieve the bit rate reduction, the proposed method achieve not only the bit rate reduction but also the performance improvement.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.3
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• pp.145-148
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• 2015

In this letter, we present a new linearization method for a voltage controlled oscillator (VCO)-based quantizer in an analog-to-digital converter (ADC). The nonlinearity of the VCO generates unwanted harmonic spurs and reduces the signal-to-noise and distortion ratio (SNDR) of the VCO-based quantizer. This letter suggests a frequency-to-current feedback method to effectively suppress harmonic distortion. The proposed method decreases the harmonic spurs by more than 53 dB. And a VCO-based quantizer employing the proposed linearization method achieves a high SNDR of 74.1 dB.

• The Journal of the Acoustical Society of Korea
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• v.17 no.4E
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• pp.35-40
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• 1998

In this paper, an efficient quantization method of line spectrum pairs(LSP) with cascaded structure of vector quantizer and scalar quantizer is proposed. First, input LSP parameters is vector-quantized using a codebook a with a moderate number of entries. In the second stage of quantization, the components of residual vector are individually quantized by the scalar quantizer. The utilization of ordering property of LSP parameters and the inclusion of interframe prediction improve the quantizer performance and remove the stability check routine after quantization procedure. The new vector-scalar hybrid quantizer using 26 bits/frame shows a transparent quality of speech that an average spectral distortion is 1 dB and the frame proportion with above 2 dB spectral distortion is less than 2%. The performances of proposed quantization method is evaluated in the transmission errors.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.42 no.3 s.303
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• pp.81-90
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• 2005

When we transmit signals, which are quantized by the vector quantizer (VQ), through noisy channels, the overall performance of the coding system is very dependent on the employed quantization scheme and the channel error effect. In order to design an optimal coding system, the source and channel coding scheme should be jointly optimized as in the channel-optimized VQ. As a suboptimal approach, we may consider the robust VQ (RVQ). In RVQ, we consider developing an index assignment function for mapping the output of quantizers to channel symbols so that the effect of the channel errors is minimized. Recently, a VQ, which can reduce the encoding complexity and is called the sample-adaptive product quantizer (SAPQ), has been proposed. SAPQ has very similar quantizer structure as to the product quantizer (PQ). However, the quantization performance can be better than PQ. Further, the encoding complexity and the memory requirement for the codebooks are lower than the regular full-search VQ case. In this paper, SAPQ is employed in order to design an RVQ to channel errors by reducing the vector dimension. Discussions on the codebook structure of SAPQ and experiments are introduced in an aspect of robustness to noisy channels.