Differential Pulse Code Modulation Research Articles

A uniform format for ocular imaging devices.

To develop a uniform file format of ocular imaging data, including, but not limited to, ultrasound biomicroscopy, optical coherence tomography, and nerve fiber analyzer, capable of being transmitted via Internet or intranet for collaborative research and telemedicine use. File filters were developed as dynamic link libraries (DLLs). These can read the original raw data format of each ocular imaging device. A data file format was also designed to describe these raw data uniformly in three different types of compression: noncompressed, run length compression, and differential pulse code modulation (DPCM). These three file formats were then tested in the following aspects: file size, speed of reading, and speed of writing. Run length compression failed to compress raw data, while DPCM compressed raw data successfully (< or =35.5%). The speed of reading and writing files was slowest in DPCM. However, the actual time of reading and writing was fast enough (<0.6 s) for daily work regardless of file compression methods. The format designed has robust potential to be the standard file format for transmission of any ocular imaging raw data.

State encoding of Hidden Markov linear prediction models

In this paper, we derive finite-dimensional non-linear filters for optimally reconstructing speech signals in Switched Prediction vocoders, Code Excited Linear Prediction (CELP) and Differential Pulse Code Modulation (DPCM). Our filter is an extension of the Hidden Markov filter.

Subband video coding with scene-adaptive hierarchical motion estimation

This paper presents a new motion-compensated subband video-coding technique using variable reference-frame positions for motion estimation. The work builds on temporal segmentation for determining the reference-frame positions and incorporates multiresolution motion estimation in the subband domain. The key advantage of the new algorithm is the complexity reduction in motion estimation that uses the multiresolution property of subband decomposition. Temporal segmentation is performed with the lowest spatial subband, based on the detection of two types of scene change. The frames of input video are split into seven spatial subbands, and the motion vectors for each subband are generated by a hierarchical motion-estimation algorithm. Blockwise differential pulse code modulation (DPCM) and a uniform quantizer are used for the lowest subband of the first frame only, and the subbands of all other cases are coded by PCM with a dead zone quantizer. Simulation results show that our scene-adaptive scheme compares favorably with a fixed interpolation structure.

Errors associated with the use of adaptive differential pulse code modulation in the compression of isometric and dynamic myo-electric signals

Muscle activity produces an electrical signal termed the myo-electric signal (MES). The MES is a useful clinical tool, used in diagnostics and rehabilitation. This signal is typically stored in 2 bytes as 12-bit data, sampled at 3 kHz, resulting in a 6 kbyte s−1 storage requirement. Processing MES data requires large bit manipulations and heavy memory storage requirements. Adaptive differential pulse code modulation (ADPCM) is a popular and successful compression technique for speech. Its application to MES would reduce 12-bit data to a 4-bit representation, providing a 3∶1 compression. As, in most practical applications, memory is organised in bytes, the realisable compression is 4∶1, as pairs of data can be stored in a single byte. The performance of the ADPCM compression technique, using a real-time system at 1 kHz, 2 kHz and 4 kHz sampling rates, is evaluated. The data used include MES from both isometric and dynamic contractions. The percent residual difference (PRD) between an unprocessed and processed MES is used as a performance measure. Errors in computed parameters, such as median frequency and variance, which are used in clinical diagnostics, and waveform features employed in prosthetic control are also used to evaluate the system. The results of the study demonstrate that the ADPCM compression technique is an excellent solution for relieving the data storage requirements of MES both in isometric and dynamic situations.

Application of biorthogonal wavelet transform to the compression of ultraviolet-visible spectra

A wavelet transform (WT) based method was proposed to compress ultraviolet–visible (UV–vis) spectra from chemical and biochemical studies. These spectra were first transformed into different sub-bands which contain information on different scales and frequency bands. The biorthogonal filter banks (BFB) coupled with the circular (CE) or symmetric extension (SE) method were employed in the WT treatment. Differential pulse code modulation (DPCM) was applied to further reduce the storage space required for the scale coefficients which were generated from the WT treatment. Then, optimal bit allocation (OBA) procedure for data quantization coupled with variable length coding (VLC) was applied to these coefficients to minimize the root-mean-square difference (RMSD) between the original and reconstructed spectra. Both synthetic and experimental spectra were used in the study. Our results show that the performance of the proposed compression methods are better than those suggested in the previous studies.

Voice over ATM using AAL2 and bit dropping: performance and call admission control

Asynchronous transfer mode (ATM) adaptation layer 2 (AAL2) has been designed for efficient transport of voice, fax, and voiceband data (VBD) traffic over an ATM virtual circuit. The protocol helps achieve low latency and high bandwidth efficiency while applying suitable compression methods on voice/VBD/fax calls and silence elimination on voice calls. We analyze the performance and capacity of an ATM multiplexer based on AAL2 adaptation. We assume that embedded adaptive differential pulse code modulation (ADPCM) is used to compress voice, and silence elimination is used to achieve statistical multiplexing gain. The embedded ADPCM coding scheme allows selective dropping of less significant bits of voice during congestion in the ATM/AAL2 multiplexer. We compare the call capacities of voice multiplexers with and without bit dropping (BD). The performance models and results presented are based on fairly general assumptions and can be used for traffic engineering and call admission control in land-line or wireless ATM systems for a variety of voice/voiceband compression algorithms. A generalized algorithm for call admission control is also described.

A 2.7-V CMOS single-chip baseband processor for CT2/CT2+ cordless telephones

A low-voltage, low-power CMOS single-chip baseband processor for CT2 and CT2+ cordless telephones is presented. The chip integrates a complete voiceband codec, a tone generator, a G721 adaptive differential pulse code modulation coder/decoder, a burst-mode logic controller for CT2/CT2+ framings, and an I/Q baseband signal generator. The only external components are made of two quartz crystals. The chip is interfaced with standard microcontrollers through a parallel interface. With a 2.7 V minimum supply, it consumes normal and standby powers of 35 mW and 25 /spl mu/W, respectively. Maximum supply is 5.5 V, and temperature range is from -40 to 70/spl deg/C. Chip area (including scribe line) is 55.5 mm/sup 2/ in a 0.8 /spl mu/m N-well double-metal single-poly CMOS process with implanted capacitors.

Low-power and high-quality signal transmission baseband LSIC for personal communications

This paper presents a very low power consumption one-chip baseband large-scale integrated circuit (LSIC) for personal communication terminals. It comprises a /spl pi//4-shift QPSK modem, an adaptive differential pulse code modulation (ADPCM) codec, a time division multiple access time division duplex (TDMA-TDD) controller and a link access procedure for a digital cordless (LAPDC: Layer-2 protocol) controller. The developed LSIC meets all the specifications of the personal handy-phone system (PHS) standard. By employing a novel coherent demodulator and an ADPCM codec with a click noise suppressor, a higher quality voice transmission has been achieved in a fading environment. In addition, it has 61-kb/s data transmission capability to achieve wireless multimedia services based on PHS. Moreover, the novel circuit configurations of the modem, the ADPCM codec, the TDMA-TDD controller, and the LAPDC controller achieve significant power reduction of the baseband circuits (57.4 mW) of personal communication terminals. It enables very low power consumption wireless multimedia terminals to be achieved based on the PHS common air interface.

An integrated method in wavelet-based image compression

In this paper, we propose an integrated image compression method, which contains the discrete wavelet transform, scalar quantization and some lossless codings, to gain higher compression ratios while maintaining the image fidelity. The discrete wavelet transform has the properties of entropy reduction and energy concentration in high frequency subimages. An innovative approach, called revised run-length coding, is proposed to improve the compression performance. The idea of this approach is to represent the appearance of symbols of the run-length code in exponential expression for saving the storage in bits. The differential pulse code modulation is used to reduce the entropy of the lowest frequency subimage of the discrete wavelet transform and to achieve high compression effects losslessly.

Reversible decorrelation method for progressive transmission of 3-D medical image.

In this paper, we present a new reversible decorrelation method of three-dimensional (3-D) medical images for progressive transmission. Progressive transmission of an image permits gradual improvement of image quality while being displayed. When the amount of image data is very large, as a 3-D medical image, the progressive transmission plays an important role in viewing or browsing the image. The data structure presented in this paper takes account of interframe correlation as well as intraframe correlation of the 3-D image. This type of data structure has been termed the 3-D hierarchy embedded differential image (3-D-HEDI) as was derived from the earlier HEDI structure. Experiments were conducted to verify the performance of 3-D HEDI in terms of the decorrelation efficiency as well as the progressive transmission efficiency. It is compared with those of conventional hierarchy interpolation (HINT), two-dimensional (2-D) HEDI and differential pulse code modulation (DPCM). Experimental results indicate that 3-D HEDI outperforms HINT, 2-D HEDI and DPCM in both decorrelation efficiency as well as the progressive transmission efficiency on 3-D medical images.

Errors associated with the use of adaptive differential pulse code modulation in the compression of isometric and dynamic myo-electric signals.

Muscle activity produces an electrical signal termed the myo-electric signal (MES). The MES is a useful clinical tool, used in diagnostics and rehabilitation. This signal is typically stored in 2 bytes as 12-bit data, sampled at 3 kHz, resulting in a 6 kbyte s-1 storage requirement. Processing MES data requires large bit manipulations and heavy memory storage requirements. Adaptive differential pulse code modulation (ADPCM) is a popular and successful compression technique for speech. Its application to MES would reduce 12-bit data to a 4-bit representation, providing a 3:1 compression. As, in most practical applications, memory is organised in bytes, the realisable compression is 4:1, as pairs of data can be stored in a single byte. The performance of the ADPCM compression technique, using a real-time system at 1 kHz, 2 kHz and 4 kHz sampling rates, is evaluated. The data used include MES from both isometric and dynamic contractions. The percent residual difference (PRD) between an unprocessed and processed MES is used as a performance measure. Errors in computed parameters, such as median frequency and variance, which are used in clinical diagnostics, and waveform features employed in prosthetic control are also used to evaluate the system. The results of the study demonstrate that the ADPCM compression technique is an excellent solution for relieving the data storage requirements of MES both in isometric and dynamic situations.

Near-lossless image compression: minimum-entropy, constrained-error DPCM

A near-lossless image compression scheme is presented. It is essentially a differential pulse code modulation (DPCM) system with a mechanism incorporated to minimize the entropy of the quantized prediction error sequence. With a "near-lossless" criterion of no more than a d gray-level error for each pixel, where d is a small nonnegative integer, trellises describing all allowable quantized prediction error sequences are constructed. A set of "contexts" is defined for the conditioning prediction error model and an algorithm that produces minimum entropy conditioned on the contexts is presented. Finally, experimental results are given.

Joint source and channel coding using turbo codes over rings

Turbo codes are a practical solution for achieving large coding gains. We present a new turbo coding scheme where the component codes are convolutional codes (CCs) over the ring of integers modulo M, with M being the alphabet size of the source encoder. The a priori knowledge of the source statistics is used during the iterative decoding procedure for improved decoder performance. As an example of application, we examine differential pulse code modulation (DPCM) encoded image transmission.

Impact of network routing on the end-to-end transmission quality of cellular and PCS connections

Long-distance and especially international calls involve an increasing number of multilink circuits of cellular, personal communications, mobile satellite, and public switched telephone network (PSTN)-type connections incorporating a variety of speech coding devices. In particular, the rapid growth of cellular communications and the impeding emergence of personal communication systems (PCSs) has highlighted the need to characterize the quality of end-to-end connections when cellular and PCS terminals are connected over the PSTN. At the same time, the nonlinear nature of low-rate parametric speech coding has rendered unsuitable known analytical methods for estimating end-to-end quality of interconnected networks. Instead, quantification of the transmission performance requires direct subjective evaluation of the pertinent connections of interest. In this paper, the quality of North American, Japanese, and European digital cellular and PCS terminals is quantified when these are interconnected using 16-kb/s low-delay code-excited linear prediction (LD-CELP) and 32-kb/s adaptive differential pulse code modulation (ADPCM) facilities. From these assessments, it can be concluded that digital cellular networks may meet end-to-end transmission planning criteria when interconnected with the switched network as long as calls are terminated to a wired terminal.

A Fuzzy Switched DPCM Predictor for Lossless Compression of Noisy Images

Differential pulse code modulation (DPCM) algorithms are widely used to compress gray-scale pictures. A critical element in a DPCM algorithm is the accurate prediction of the pixel gray-levels in the input picture. The switched predictors used in modern DPCM algorithms are generally accurate when the input picture is free of noise. However, even small amounts of noise in the input picture will cause a substantial reduction in prediction accuracy and in turn a reduction in compression efficiency. In this paper we describe a novel fuzzy rule-based predictor for use in a lossless DPCM algorithm. For noisy pictures, the accuracy of the new predictor is consistently higher than the accuracy of standard switched predictors.

Hybrid block truncation coding

A hybrid block truncation coding (BTC) is presented. In the hybrid BTC, a universal codebook using Hamming codes and a differential pulse code modulation (DPCM) are employed, respectively, to the bit plane and the side information of BTC to reduce coding rate. Simulation results reveal that the performance of the proposed algorithm is only slightly worse than that of the hybrid BTC using vector quantization (VQ) techniques, but with much lower computational or hardware complexity.

A video compression scheme with optimal bit allocation among segmentation, motion, and residual error

We present a theory for the optimal bit allocation among quadtree (QT) segmentation, displacement vector field (DVF), and displaced frame difference (DFD). The theory is applicable to variable block size motion-compensated video coders (VBSMCVC), where the variable block sizes are encoded using the QT structure, the DVF is encoded by first-order differential pulse code modulation (DPCM), the DFD is encoded by a block-based scheme, and an additive distortion measure is employed. We derive an optimal scanning path for a QT that is based on a Hilbert curve. We consider the case of a lossless VBSMCVC first, for which we develop the optimal bit allocation algorithm using dynamic programming (DP). We then consider a lossy VBSMCVC, for which we use Lagrangian relaxation, and show how an iterative scheme, which employs the DP-based solution, can be used to find the optimal solution. We finally present a VBSMCVC, which is based on the proposed theory, which employs a DCT-based DFD encoding scheme. We compare the proposed coder with H.263. The results show that it outperforms H.263 significantly in the rate distortion sense, as well as in the subjective sense.

Novel nonlinear predictive image coding algorithm

We present a novel nonlinear predictive image coding scheme in which a relative prediction error is first generated from the current pixel value and its predicted value. It is next mapped, quantized, coded and transmitted. Consequently, a weighting function is introduced into the coding algorithm such that the coding error is adapted by the pixel intensity and its relative prediction error. Meanwhile, the resulting quantization step size is smaller in lower contrast areas and larger in higher contrast areas so that the granular noise and the slope overload distortion can be efficiently reduced. Our simulation results show that on an average, with the proposed scheme, the bit rate is about 0.23 bits less than that obtained with differential pulse-code modulation (DPCM), while the peak SNR (PSNR) is about 2.9 dB higher than that with DPCM. On the other hand, more coding errors are allocated in less visible areas where the image intensity and/or contrast are higher.

Hyperspectral image compression using entropy-constrained predictive trellis coded quantization

A training-sequence-based entropy-constrained predictive trellis coded quantization (ECPTCQ) scheme is presented for encoding autoregressive sources. For encoding a first-order Gauss-Markov source, the mean squared error (MSE) performance of an eight-state ECPTCQ system exceeds that of entropy-constrained differential pulse code modulation (ECDPCM) by up to 1.0 dB. In addition, a hyperspectral image compression system is developed, which utilizes ECPTCQ. A hyperspectral image sequence compressed at 0.125 b/pixel/band retains an average peak signal-to-noise ratio (PSNR) of greater than 43 dB over the spectral bands.

IMAGE COMPRESSION SCHEME WITH EMBEDDED MULTILEVEL BLOCK TRUNCATION CODING BASED ON HUMAN VISUAL EFFECT

ABSTRACT In this paper, we first propose a new embedded multilevel block truncation coding (BTC) technique. Unlike Differential pulse code modulation (DPCM), Vector quantization (VQ), and general multilevel BTC algorithms which determine the image quality at a time, the embedded multilevel BTC improves the image quality largely and progressively until obtaining an image with excellent quality. In order to reduce the bit rate efficiently, we propose a perception model and utilize it to develop a pruning algorithm. The pruning algorithm removes the useless information, which the human eyes are not sensitive, generated by the embedded multilevel BTC. The simulation results indicate that the bit rate with the proposed method is much less than that with the DPCM and general multilevel BTC under the same objective criterion, PSNR, or subjective criterion. This paper also shows that the computation complexity of the proposed method is much less than that with VQ under the same high quality reconstructed image.