Showing papers in "Signal Processing-image Communication in 1998"
TL;DR: A novel method for the segmentation of faces, extraction of facial features and tracking of the face contour and features over time, using deformable models like snakes is described.
Abstract: The present paper describes a novel method for the segmentation of faces, extraction of facial features and tracking of the face contour and features over time. Robust segmentation of faces out of complex scenes is done based on color and shape information. Additionally, face candidates are verified by searching for facial features in the interior of the face. As interesting facial features we employ eyebrows, eyes, nostrils, mouth and chin. We consider incomplete feature constellations as well. If a face and its features are detected once reliably, we track the face contour and the features over time. Face contour tracking is done by using deformable models like snakes. Facial feature tracking is performed by block matching. The success of our approach was verified by evaluating 38 different color image sequences, containing features as beard, glasses and changing facial expressions.
334 citations
TL;DR: The results showed that the subjective quality of a stereo image sequence fell approximately midway between the quality of the left- and right-eye views, consistent with known properties of binocular vision, in particular with the averaging of brightness and contrast of stimuli presented to the two eyes.
Abstract: The present research assessed the subjective image-quality of stereo sequences where the left- and right-eye views differed in severity of compression. Viewers watched image sequences where the left-eye view was displayed at a higher quality than the right-eye view, and rated the combined overall subjective image-quality of the sequence. Three stereo image sequences were used for assessment. Each sequence, in the ITU-R 601 format, was 10 s in duration and the images for the left-eye view were coded independently of the right-eye view, at bit-rates of 6, 3, 2 and 1 Mbits/s, using MPEG-2, Main Profile/Main Level syntax. These were combined to generate stereo sequences where the bit-rates were (left : right) 6 : 6, 6 : 3, 6 : 2, 6 : 1, 3 : 3, 3 : 2 and 3 : 1. The resulting stereo sequences were viewed by 26 subjects, and rated in terms of subjective image-quality. The rating methodology was based on the double-stimulus continuous-quality scale method described in ITU-R Recommendation 500. The results showed that the subjective quality of a stereo image sequence fell approximately midway between the quality of the left- and right-eye views. The results are consistent with known properties of binocular vision, in particular with the averaging of brightness and contrast of stimuli presented to the two eyes.
95 citations
TL;DR: This paper describes a hardware system and the underlying algorithms that were developed for realtime stereoscopic videoconferencing with viewpoint adaptation within the European PANORAMA project to achieve a true telepresence illusion for the remote partners.
Abstract: This paper describes a hardware system and the underlying algorithms that were developed for realtime stereoscopic videoconferencing with viewpoint adaptation within the European PANORAMA project. The goal was to achieve a true telepresence illusion for the remote partners. For this purpose, intermediate views at arbitrary positions must be synthesized from the views of a stereoscopic camera system with rather large baseline. The actual viewpoint is adapted according to the head position of the viewer, such that the impression of motion parallax is produced. The whole system consists of a disparity estimator, stereoscopic MPEG-2 encoder, disparity encoder and multiplexer at the transmitter side, and a demultiplexer, disparity decoder, MPEG-2 decoder and interpolator with viewpoint adaptation at the receiver side. For transmission of the encoded signals, an ATM network is provided. In the final system, autostereoscopic displays will be used. The algorithms for disparity estimation, disparity encoding and disparity-driven intermediate viewpoint synthesis were specifically developed under the constraint of hardware feasibility.
70 citations
TL;DR: This paper proposes three Huffman coding methods in which pre-defined codebooks are effectively manipulated according to local symbol statistics, and combines these methods to further improve compression efficiency.
Abstract: In many image sequence compression applications, Huffman coding is used to eliminate statistical redundancy resident in given data. The Huffman table is often pre-defined to reduce coding delay and table transmission overhead. Local symbol statistics, however, may be much different from the global ones manifested in the pre-defined table. In this paper, we propose three Huffman coding methods in which pre-defined codebooks are effectively manipulated according to local symbol statistics. The first proposed method dynamically modifies the symbol-codeword association without rebuilding the Huffman tree itself. The encoder and decoder maintain identical symbol-codeword association by performing the same modifications to the Huffman table, thus eliminating extra transmission overhead. The second method adaptively selects a codebook from a set of given ones, which produces the minimum number of bits. The transmission overhead in this method is the codebook selection information, which is observed to be negligible compared with the bit saving attained. Finally, we combine the two aforementioned methods to further improve compression efficiency. Experiments are carried out using five test image sequences to demonstrate the compression performance of the proposed methods.
66 citations
TL;DR: It is seen that the presence of a third camera at the transmitter site improves the estimation of disparities, the detection of occlusions and the accuracy of the resulting spatial interpolation at the receiver.
Abstract: In the present paper techniques are examined for the coding of the depth map and disparity fields for stereo or multiview image communication applications. It is assumed that both the left and right channels of the multiview image sequence are coded using block- or object-based methods. A dynamic programming algorithm is used to estimate a disparity field between each stereo image pair. Depth is then estimated and occlusions are optionally detected, based on the estimated disparity fields. Spatial interpolation techniques are examined based on the disparity/depth information and the detection of occluded regions using either stereoscopic or trinocular camera configurations. It is seen that the presence of a third camera at the transmitter site improves the estimation of disparities, the detection of occlusions and the accuracy of the resulting spatial interpolation at the receiver. Various disparity field and depth map coding techniques are then proposed and evaluated, with emphasis given to the quality of the resulting intermediate images at the receiver site. Block-based and wireframe modeling techniques are examined for the coding of isolated depth or disparity map information. Further, 2D and 3D motion compensation techniques are evaluated for the coding of sequences of depth or disparity maps. The motion fields needed may be available as a byproduct of block-based or object-based coding of the intensity images. Experimental results are given for the evaluation of the performance of the proposed coding and spatial interpolation methods.
64 citations
TL;DR: The method found to work best uses a motion-compensated three-field vertical-temporal filter, in which the vertical component of the vector is rounded to the nearest even number of picture lines per field period.
Abstract: The conversion of interlaced video to progressive format may be carried out in a number of ways, including vertical interpolation, fixed or motion-compensated vertical-temporal interpolation, and approaches based on motion compensation using non-uniform sampling theory. Motion-compensated methods potentially offer the best performance, although the accuracy and reliability of the vectors has a significant impact on their performance. For applications such as display conversion using vectors recovered from an MPEG-2 bitstream, the vectors available may not be of the highest quality. This paper considers several motion-compensated interlace-to-progressive conversion methods, and assesses their performance with both accurate and inaccurate vectors using objective and subjective techniques. The method found to work best uses a motion-compensated three-field vertical-temporal filter, in which the vertical component of the vector is rounded to the nearest even number of picture lines per field period. This method reduced the RMS error of converted picture sequences by almost 20% compared to simple vertical filtering when using vectors from an MPEG-2 bitstream. Conversely, some other motion-compensated methods were found to increase the error by a similar amount.
57 citations
TL;DR: An analysis of the basic approaches to autostereoscopic 3D display is presented, and a new single LCD flat panel display is described in which observer tracking can be achieved without a requirement for moving parts.
Abstract: An analysis of the basic approaches to autostereoscopic 3D display is presented, together with a discussion of the application of liquid crystal displays (LCDs) in this field. We show that of particular importance in the design of such displays is the illumination optical system and the optical quality of viewing windows produced. The window illumination quality determines many performance criteria including image fidelity, cross talk, viewing freedom and observer dynamics in a wide range of displays. The effects of degradation in window structure are described. Recent progress in 3D systems incorporating two LCD panels based on bulk and micro-optic systems is described. Further a new single LCD flat panel display is described in which observer tracking can be achieved without a requirement for moving parts. We detail the modifications to the LCD pixel structure necessary and how tracking may be achieved by manipulating the video information presented to the display panel.
51 citations
TL;DR: A new motion estimation algorithm which determines an initial motion vector and a search window adaptively in video codecs which code and transmit data in a block scan order is presented.
Abstract: In this paper, we present a new motion estimation algorithm which determines an initial motion vector and a search window adaptively in video codecs which code and transmit data in a block scan order. The proposed method is based on the motion information of spatio-temporal neighboring blocks. In predicting the motion, a temporal projection technique is introduced in the determination of an initial vector, and then the search window size to refine the initial vector is determined by the correlation between neighboring blocks. With a small amount of computation during motion estimation, the proposed algorithm can estimate the motion of fast moving object. Experimental results of the proposed method show significantly improved performance in image quality and the computational complexity.
44 citations
TL;DR: A new block reduction technique is proposed, based on a space-variant non-linear filtering operation of the blocking artifacts present in the image to be reconstructed, which provides a way to greatly reduce the artifacts without degrading high-frequency information of the original image.
Abstract: Blocking effect constitutes one of the main drawbacks of the actual DCT-based compression methods. We propose in this paper a new block reduction technique; it is based on a space-variant non-linear filtering operation of the blocking artifacts present in the image to be reconstructed. To account for the perceptual importance of the distortion, the amount of smoothing is adapted to the visibility of the blocking effect. A visibility parameter is computed for each artifact using the psychovisual properties of the human visual system (HVS). The postprocessing algorithm is in conformity with actual existing compression standards; it provides a way to greatly reduce the artifacts without degrading high-frequency information of the original image. First the proposed method is described and then experimental results are presented, showing the effectiveness of the correction.
41 citations
TL;DR: A hierarchical estimation scheme that attempts to acquire a sharp depth map such that edges of the depth map coincide with object boundaries on the one hand, and reduce noisy estimates due to insufficient size of matching window on the other hand is proposed.
Abstract: We present a method to estimate a dense and sharp depth map using multiple cameras. A key issue for obtaining sharp depth map is how to overcome the harmful influence of occlusion. Thus, we first propose an occlusion-overcoming strategy which selectively uses the depth information from multiple cameras. With a simple selection technique, we resolve the occlusion problem considerably at a slight sacrifice of noise tolerance. Another key issue in area-based stereo matching is the size of matching window. We propose to use a hierarchical estimation scheme that attempts to acquire a sharp depth map such that edges of the depth map coincide with object boundaries on the one hand, and reduce noisy estimates due to insufficient size of matching window on the other hand. Owing to the unique property of occlusion-overcoming strategy, we can utilize full benefit of hierarchical schemes. We show the method can produce a sharp and correct depth map for a variety of images.
40 citations
TL;DR: A blockwise distortion measure is proposed for evaluating the visual quality of compressed images, which outperforms PQS for a set of test images, and is much simpler to implement.
Abstract: A blockwise distortion measure is proposed for evaluating the visual quality of compressed images. The proposed measure calculates quantitatively how well important visual properties have been preserved in the distorted image. The method consists of three quality factors detecting contrast errors, structural errors, and quantization errors. The proposed method outperforms PQS for a set of test images, and is much simpler to implement. The method should also be applicable to color images; properties like color richness and saturation are captured by the quantization and contrast measures, respectively.
TL;DR: The improved concept is based on a modified block matching algorithm in which a cost function consisting of feature- and area-based correlation together with an appropriately weighted temporal smoothness term is applied to synthesize temporally and perspectively intermediate views in stereo sequences.
Abstract: An improved method for combined motion and disparity estimation in stereo sequences to synthesize temporally and perspectively intermediate views is presented. The main problems of matching methods for motion and disparity analysis are summarised. The improved concept is based on a modified block matching algorithm in which a cost function consisting of feature- and area-based correlation together with an appropriately weighted temporal smoothness term is applied. Considerable improvements have been obtained with respect to the motion and disparity assignments by introducing a confidence measure to evaluate the reliability of estimated correspondences. In occluded image areas, enhanced results are obtained applying an edge-assisted vector interpolation strategy. Two different image synthesis concepts are presented. The first concept is suitable for processing natural stereo sequences. It comprises the detection of covered and uncovered image areas caused by motion or disparity. This information is used to switch between different interpolation and extrapolation modes during the computation of intermediate views. The proposed object-based approach is suitable for processing typical video conference scenes containing extremely large occluded image regions and keeping implementation costs low. A set of stereo sequences has been processed. The performed computer simulations show that a continuous motion parallax can be obtained with good image quality by using sequences taken with stereo cameras having large interaxial distances.
TL;DR: This paper presents a novel motion estimate scheme, called correlation search, which attempts to find the highest motion-correlation neighbor block from the spatial and temporal neighbor blocks.
Abstract: Block-matching motion estimation plays an important role in video coding. In general, there exists a high motion correlation between neighbor blocks in spatial and temporal directions. This paper presents a novel motion estimate scheme, called correlation search, which attempts to find the highest motion-correlation neighbor block from the spatial and temporal neighbor blocks. The motion vector of the highest motion-correlation neighbor block is regarded as the motion estimate of the current block. The correlation search scheme can be based on any existing block matching algorithms. When the scheme is based on a full-search algorithm, it achieves almost the same estimate accuracy with a significant reduction of computational complexity. If the scheme is based on a fast search algorithm, it obtains better estimate accuracy in addition to the improvements in computation.
TL;DR: While DISTIMA made it possible to transmit stereoscopic video compatible to MPEG 2 in real time, PANORAMA develops a 3-D video system: viewpoint adaptive visualisation of scenes providing look-around-capability.
Abstract: In the last years two European projects – DISTIMA and PANORAMA – were working on stereoscopic and three-dimensional (3-D) video. While DISTIMA made it possible to transmit stereoscopic video compatible to MPEG 2 in real time, PANORAMA develops a 3-D video system: viewpoint adaptive visualisation of scenes providing look-around-capability. This paper describes selected parts of the work performed in the two projects: the DISTIMA real-time hardware for the MPEG2 compatible transmission of stereoscopic video, the DISTIMA activities in the area of region and object-based stereoscopic coding, the PANORAMA real-time hardware development for 3-D video based on disparity estimation and disparity compensated interpolation of intermediate views and the PANORAMA software development for 3-D video based on 3-D reconstruction and 3-D computer graphics.
TL;DR: A general and robust approach to the problem of close-range 3D reconstruction of objects from stereo correspondence of luminance patches, which takes into account the viewer-dependent radiometric distortion as well.
Abstract: In this article we present a general and robust approach to the problem of close-range 3D reconstruction of objects from stereo correspondence of luminance patches. The method is largely independent on the camera geometry, and can employ an arbitrary number of CCD cameras. The robustness of the approach is due to the physicality of the matching process, which is performed in the 3D space. In fact, both 3D location and local orientation of the surface patches are estimated, so that the geometric distortion can be accounted for. The method takes into account the viewer-dependent radiometric distortion as well. The method has been implemented with a calibrated set of three standard TV-resolution CCD cameras. Experiments on a variety of real scenes have been conducted with satisfactory results. Quantitative and qualitative results are reported.
TL;DR: An experimental study on the applicability of selective repeat ARQ for one way real time video applications is presented, and the proposed ARQ schemes greatly reduce the packet errors, when used along with optimal decoder buffer control and source interleaving.
Abstract: New schemes for video transmission over wireless channels are described. Content based approaches for video segmentation and associated resource allocation are proposed. We argue that for transport over wireless channels, different video content requires different form of resource allocation. Content and data dependent FEC/ARQ schemes are used to do adaptive resource allocation after segmentation. FEC based schemes are used to provide class dependent error robustness and a modified ARQ technique is used to provide constrained delay and loss. The approach is compatible with video coding standards such as H.261 and H.263. We use frame-type (extent of intra coding), scene changes, and motion based procedures to provide finer level of control for data segmentation in addition to standard headers and data-type (motion vectors, low and high frequency DCTs) based segmentation. An experimental simulation platform is used to test the objective (SNR) and subjective effectiveness of proposed algorithms. The FEC schemes improve both objective and subjective video quality significantly. An experimental study on the applicability of selective repeat ARQ for one way real time video applications is also presented. We study constraints of using ARQ under display constraints, limited buffering requirements and small initial startups. The proposed ARQ schemes greatly reduce the packet errors, when used along with optimal decoder buffer control and source interleaving. The common theme integrating the study of FEC and ARQ algorithms is the content based resource allocation for wireless video transport.
TL;DR: Kriging is a linear interpolation method used by geostatisticians and it is shown that it can be successfully applied to image sequence coding and improved with an optimization method that is named ‘inverse kriging’.
Abstract: Kriging is a linear interpolation method used by geostatisticians. In this paper we show that it can be successfully applied to image sequence coding. First we apply it to texture coding and we improve these preliminary results with an optimization method that we have named ‘inverse kriging’. Then we apply kriging and inverse kriging to motion vector fields, which are by essence smooth within an object. We show an application of these tools in the framework of the active mesh coding scheme developed within the RACE/Morpheco project.
TL;DR: Simulation results indicate that the new filters suppress impulsive as well as Gaussian noise and preserve edges and details in multichannel images.
Abstract: This paper addresses the problem of noise suppression for multichannel data, such as colour images. The proposed filters utilize adaptive data dependent nonparametric techniques. Simulation results indicate that the new filters suppress impulsive as well as Gaussian noise and preserve edges and details.
TL;DR: Performance results based on the proposed CSCC system indicate that the proposed system achieves a throughput as high as 70% with good visual quality at PSNRs (peak signal-to-noise ratio) around 30 dB for the reconstructed images.
Abstract: In this paper, we propose an efficient image transmission system for reliable transmission of vulnerable compressed images over mobile radio channels. The image coder is fully compatible with the JPEG baseline coding standard. Its transmission system is designed based on lossy transmission with combined source and channel coding (CSCC) and low complexity error concealment. Specifically, the proposed CSCC uses block codes which are designed to match both the coded image characteristics and wireless channel statistics, thereby accomplishing efficient transmission along with good visual quality. Together with a block-shuffling scheme, a simple error-concealment technique is introduced to effectively reconstruct the damaged image blocks caused by the residual errors. It is shown that the proposed techniques are applicable to mobile image transmission with different compression ratios under various mobile channel conditions. Performance results based on images `LENA' and `AIRPLANE', which are coded at 0.85 and 0.90 bit/pixel, respectively, under the simulated GSM channel (Pan-European Cellular Standard) with an average SNR (signal-to-noise ratio) of 18 dB and various vehicle speeds (2–50 miles/h) indicate that the proposed system achieves a throughput as high as 70% with good visual quality at PSNRs (peak signal-to-noise ratio) around 30 dB for the reconstructed images.
TL;DR: Instead of complex vector quantization, which is commonly used in subband image coding for high compression ratio, simple scalar quantization is used to code the remaining coefficients and achieves very good results.
Abstract: Wavelet transform can decompose images into various multiresolution subbands. In these subbands the correlation exists. A novel technique for image coding by taking advantage of the correlation is addressed. It is based on predictive edge detection from the LL band of the lowest resolution level to predict the edge in the LH, HL and HH bands in the higher resolution level. If the coefficient is predicted as an edge it is preserved; otherwise, it is discarded. In the decoder, the location of the preserved coefficients can also be found as in the encoder. Therefore, no overhead is needed. Instead of complex vector quantization, which is commonly used in subband image coding for high compression ratio, simple scalar quantization is used to code the remaining coefficients and achieves very good results.
TL;DR: The proposed coding algorithm has low computational complexity, is based on the widely used 8 × 8 2D-DCT, and thus, can be readily implemented using existing block-based coding standards such as JPEG, H.261, MPEG.
Abstract: In this paper, a new texture coding algorithm for arbitrarily shaped image segments is introduced. In contrast to other methods described in the literature, the proposed coding algorithm has low computational complexity, is based on the widely used 8 × 8 2D-DCT, and thus, can be readily implemented using existing block-based coding standards such as JPEG, H.261, MPEG. And the content based functionalities currently discussed in the MPEG-4 standardization phase can be easily achieved with the proposed algorithm. Computer simulations and comparisons with other results from the literature reveal that our proposed technique is quite promising and competitive.
TL;DR: This paper describes a new approach to finding the optimal solutions of the color image quantization problem using a genetic algorithm and the superior quality of the results of the GA is shown.
Abstract: The need for quantization of color images arises because of limitations of image display and hardcopy, data storage and data transmission devices. Many of the present algorithms for color quantization find non-optimal solutions, giving rise to visible shifts in color and false contours when the number of quantization colors is small. This paper describes a new approach to finding the optimal solutions of the color image quantization problem using a genetic algorithm. The nature and the difficulty of the problem and its formulation are discussed. Then genetic algorithms (GAs) are presented and the representation of the problem with this method is explained. The effect of the parameters such as mutation and crossover probabilities and population size on the quality of solutions is studied. Solutions obtained with genetic algorithms are compared with those of heuristics and the K-means clustering algorithm and the superior quality of the results of the GA is shown.
TL;DR: In this paper, a model-based coding of all channels of a multiview image sequence is described, where the 3D model is initialised by accurate adaptation of a 2D wireframe model to the foreground object of one of the views.
Abstract: This paper describes a procedure for model-based coding of all channels of a multiview image sequence. The 3D model is initialised by accurate adaptation of a 2D wireframe model to the foreground object of one of the views. The rigid 3D motion is estimated for each triangle, and spatial homogeneity neighbourhood constraints are used to improve the reliability of the estimation efficiency and to smooth the motion field produced. A novel technique is used to estimate flexible motion of the nodes of the wireframe from the rigid 3D motion vectors of the wireframe triangles containing each node. Kalman filtering is used to track both rigid 3D motion of each triangle and flexible deformation of each node of the wireframe. The performance of the resulting 3D flexible motion estimation method is evaluated experimentally.
TL;DR: An adaptive disparity map modelling and coding method based on Delaunay triangulation provides an efficient and progressive format to represent disparity map information and can obtain satisfactory disparity estimation results with less computational cost.
Abstract: The paper proposes an adaptive disparity map modelling and coding method based on Delaunay triangulation. It provides an efficient and progressive format to represent disparity map information. Experiments showed that the method is promising and extendable. A hierarchical and adaptive disparity estimation algorithm which can obtain satisfactory disparity estimation results with less computational cost is also presented.
TL;DR: Experimental results show the potential applicability of the proposed method for interpolating light rays, a display-independent method for representing 3-D scenes/ objects, to the next-generation 3- D image communication and virtual reality systems.
Abstract: First, this paper explains the concept of the ‘Integrated 3-D Visual Communication System’, aiming to realize a display-independent method for representing 3-D scenes/objects. This concept will promote the progress of 3-D image communication systems, while several 3-D display technologies are making rapid progress. Secondly, a ray-based method is developed as a fundamental approach to realize this concept, and three types of parameterization of light rays are formulated. The main proposal of this paper is the utilization of orthographic views, which are neutral for any input and output system. Once a set of orthographic views of a 3-D scene/object is obtained, we can synthesize its any perspective view while viewing it from within a visual zone. Thirdly, in order to enhance the visual effects, a method for interpolating light rays is also proposed. In this method, structural properties, estimated from input images, are utilized. The advantage of the proposed method is that the visibility of estimation errors of structural properties is effectively suppressed in the synthesized views. Experimental results show the potential applicability of the proposed method to the next-generation 3-D image communication and virtual reality systems.
TL;DR: Techniques are presented for the compression of visualisations of 3D image data for efficient storage and transmission and recommendations are made for the implementation of coders of stereo views of3D medical data.
Abstract: The transmission of the large store of information contained in 3D medical data sets through limited capacity channels, is a critical procedure in many telemedicine applications. In this paper, techniques are presented for the compression of visualisations of 3D image data for efficient storage and transmission. Methods are first presented for the transmission of the 3D surface of the objects using contour following methods. Alternatively, the visualisation at the receiver may be based on a series of depth maps corresponding to some motion of the object, specified by the medical observer. Depth maps may be transmitted by using depth map motion compensated prediction. Alternatively, a wire-mesh model of the depth map may be formed and transmitted by encoding the motion of its nodes. All these methods are used for the transmission of the 3D image with visualisation carried out at the receiver. Methods are also developed for efficient transmission of the images visualised at the encoder site. These methods allow remote interactive manipulation (rotation, translation, zoom) of the 3D objects, and may be implemented even if the receiver is a relatively simple and inexpensive workstation or a simple monitor. In all above cases, the coding of binocular views of the 3D scene is examined and recommendations are made for the implementation of coders of stereo views of 3D medical data.
TL;DR: The selection of Bose–Chaundhuri–Hocquenghem error correction codes for two-layer system is examined, and it is effective to apply forward error correction (FEC) codec to only base significant layer to get higher system performance.
Abstract: This paper proposes a robust hierarchical image transmission system based on the hierarchical quadrature amplitude modulation (QAM) scheme, which gives high-quality image transmission in a band-limited Rayleigh fading channel. Authors examine the selection of Bose–Chaundhuri–Hocquenghem (BCH) error correction codes for two-layer system, and clarified that it is effective to apply forward error correction (FEC) codec to only base significant layer to get higher system performance. By using BCH(63,45,3) code for significant layer, there is about 10 dB improvement of the robustness against channel CNR degradation, with slightly image quality degradation in higher channel CNR region. Authors also analyzed the optimum hierarchical parameter in the Rayleigh fading channel which maximizes the received image quality. Using optimized hierarchical modulation, there is another 2 dB improvement of the robustness against channel CNR degradation.
TL;DR: It is found that it is errors in variable length encoded data which cause the greatest artifacts as errors in these data can cause loss of bitstream synchronisation.
Abstract: We consider the performance of MPEG-II compressed video when transmitted over noisy channels. We present the results of bit sensitivity and resynchronisation sensitivity measurements, and propose techniques for substantially improving the resilience of MPEG-II to transmission errors without the addition of any extra redundancy into the bitstream. We find that it is errors in variable length encoded data which cause the greatest artifacts as errors in these data can cause loss of bitstream synchronisation. We develop the concept of a ‘black-box transcoder’ where we losslessly transcode MPEG-II into a different structure for transmission. We achieve bitstream-resynchronisation using a technique known as error-resilient entropy coding (EREC). Finally we improve the error-resilience of differentially coded information by replacing the standard 1D-DPCM with a more resilient hierarchical pyramid predictor. We consider the transmission of MPEG-II over three separate channels: a channel subject to random bit errors, a channel subject to burst errors, and a channel subject to ATM cell losses.
TL;DR: The extent of the region of space which can be displayed in three dimensions without causing undue eye strain to the observer, and also the minimum detectable depth interval, are related to and may be controlled by the system's geometrical and optical parameters.
Abstract: The performance of stereoscopic television systems and its dependence on various parameters are investigated. It is shown that the extent of the region of space which can be displayed in three dimensions without causing undue eye strain to the observer, and also the minimum detectable depth interval, are related to and may therefore be controlled by the system's geometrical and optical parameters. Distortion in three-dimensional images due to the difference between the depth magnification and the magnification of the xy-plane is also analysed. Finally, it is demonstrated that the expressions defining the relationship between the performance of a 3D television system and its various parameters form a useful basis for the design of a system of this type for a given application.
TL;DR: Experimental results show that the computation efficiency of the proposed algorithm is significantly improved when compared to the original BTC.
Abstract: This paper presents a modified block truncation coding (BTC) algorithm for image compression Similar blocks in an image are merged into a cluster and represented with the cluster center Each cluster center is then encoded with a vision block truncation coding (VBTC) algorithm which uses a small set of predefined binary edge patterns to approximate the bit plane of the cluster center Experimental results show that the computation efficiency of the proposed algorithm is significantly improved when compared to the original BTC