Showing papers on "Video quality published in 1996"

Perceptual quality measure using a spatiotemporal model of the human visual system

Abstract: This paper addresses the problem of quality estimation of digitally coded video sequences. The topic is of great interest since many products in digital video are about to be released and it is thus important to have robust methodologies for testing and performance evaluation of such devices. The inherent problem is that human vision has to be taken into account in order to assess the quality of a sequence with a good correlation with human judgment. It is well known that the commonly used metric, the signal-to-noise ratio is not correlated with human vision. A metric for the assessment of video coding quality is presented. It is based on a multi- channel model of human spatio-temporal vision that has been parameterized for video coding applications by psychophysical experiments. The visual mechanisms of vision are simulated by a spatio-temporal filter bank. The decomposition is then used to account for phenomena as contrast sensitivity and masking. Once the amount of distortions actually perceived is known, quality estimation can be assessed at various levels. The described metric is able to rate the overall quality of the decoded video sequence as well as the rendition of important features of the sequence such as contours or textures.

Packet loss resilience of MPEG-2 scalable video coding algorithms

Abstract: Transmission of compressed video over packet networks with nonreliable transport benefits when packet loss resilience is incorporated into the coding. One promising approach to packet loss resilience, particularly for transmission over networks offering dual priorities such as ATM networks, is based on layered coding which uses at least two bitstreams to encode video. The base-layer bitstream, which can be decoded independently to produce a lower quality picture, is transmitted over a high priority channel. The enhancement-layer bitstream(s) contain less information, so that packet losses are more easily tolerated. The MPEG-2 standard provides four methods to produce a layered video bitstream: data partitioning, signal-to-noise ratio scalability, spatial scalability, and temporal scalability. Each was included in the standard in part for motivations other than loss resilience. This paper compares the performance of these techniques (excluding temporal scalability) under various loss rates using realistic length material and discusses their relative merits. Nonlayered MPEG-2 coding gives generally unacceptable video quality for packet loss ratios of 10/sup -3/ for small packet sizes. Better performance can be obtained using layered coding and dual-priority transmission. With data partitioning, cell loss ratios of 10/sup -4/ in the low-priority layer are definitely acceptable, while for SNR scalable encoding, cell loss ratios of 10/sup -3/ are generally invisible. Spatial scalable encoding can provide even better visual quality under packet losses; however, it has a high implementation complexity.

Apparatus for detecting a cut in a video

Abstract: Apparatus for detecting a cut in a video comprises arrangements for acquiring video images from a source, for deriving from the video images a pixel-based difference metric, for deriving from the video images a distribution-based difference metric, and for measuring video content of the video images to provide up-to-date test criteria. Arrangements are included for combining the pixel-based difference metric and the distribution-based difference metric, taking into account the up-to-date test criteria provided so as to derive a scene change candidate signal and for filtering the scene change candidate signal so as to generate a scene change frame list.

Traffic and video quality with adaptive neural compression

Abstract: Video sequences are major sources of traffic for broadband ISDN networks, and video compression is fundamental to the efficient use of such networks. We present a novel neural method to achieve real-time adaptive compression of video. This tends to maintain a target quality of the decompressed image specified by the user. The method uses a set of compression/decompression neural networks of different levels of compression, as well as a simple motion-detection procedure. We describe the method and present experimental data concerning its performance and traffic characteristics with real video sequences. The impact of this compression method on ATM-cell traffic is also investigated and measurement data are provided.

Low bit-rate video compression with neural networks and temporal subsampling

Abstract: In this paper we describe a novel neural network technique for video compression, using a "point-process" type neural network model we have developed which is closer to biophysical reality and is mathematically much more tractable than standard models. Our algorithm uses an adaptive approach based upon the users' desired video quality Q, and achieves compression ratios of up to 500:1 for moving gray-scale images, based on a combination of motion detection, compression, and temporal subsampling of frames. This leads to a compression ratio of over 1000:1 for full-color video sequences with the addition of the standard 4:1:1 spatial subsampling ratios in the chrominance images. The signal-to-noise ratio ranges from 29 dB to over 34 dB. Compression is performed using a combination of motion detection, neural networks, and temporal subsampling of frames. A set of neural networks is used to adaptively select the desired compression of each picture block as a function of the reconstruction quality. The motion detection process separates out regions of the frame which need to be retransmitted. Temporal subsampling of frames, along with reconstruction techniques, lead to the high compression ratios.

Bandwidth renegotiation for VBR video over ATM networks

Abstract: A scheme for delivery or variable bit-rate (VBR) video over asynchronous transfer mode (ATM) networks where bandwidth can be renegotiated during the duration of a call between the video source and the network is considered. Renegotiation can be initiated by either the video source or the network. The video bandwidth requirement is characterized by a usage parameter control (UPC) consisting, in general, of peak rate, burst length, and sustained rate. A baseline design is outlined where rate-control adjusts the source's rate while a new UPC is requested from the network. When granted, the new UPC allows the source to maintain its target quantization and delay requirements. Rate control epochs may be extended when the network blocks UPC requests or sets a lower UPC value to temporally deal with congestion. Simulation results are presented for VBR MPEG video. The results show that with a moderate renegotiation rate the scheme tracks the bandwidth requirements of the source. As a result, the video quality and bandwidth efficiency can be maintained.

Color moving pictures quality metric

Abstract: This paper presents a comprehensive quality metric for color moving pictures which is based on a spatio-temporal vision model and on the opponent-colors theory. The metric is used to assess the quality of MPEG compressed video streams and is compared with a grayscale video quality metric.

Characterization of Quality and Traffic for Various Video Encoding Schemes and Various Encoder Control Schemes

Abstract: Lossy video compression algorithms, such as those used in the H.261, MPEG, and JPEG standards, result in quality degradation seen in the form of digital tiling, edge busyness, and mosquito noise. The encoder parameters (typically, the so-called quantizer scale) can be adjusted to trade-off encoded video quality and bit rate. Clearly, when more bits are used to represent a given scene, the quality gets better. However, for a given set of encoder parameter values, both the generated traffic and the resulting quality depend on the scene content. Therefore, in order to achieve certain quality and traffic objectives at all times, the encoder parameters must be appropriately adjusted according to the scene content. Currently, two schemes exist for setting the encoder parameters. The most commonly used scheme today is called Constant Bit Rate (CBR), where the encoder parameters are controlled to achieve a target bit rate over time by considering a hypothetical rate control buffer at the encoder''s output which is drained at the target bit rate; the buffer occupancy level is used as feedback to control the quantizer scale. In a CBR encoded video stream, the quality varies in time, since the quantizer scale is controlled to achieve a constant bit rate regardless of the scene complexity. In the other existing scheme, called Open-Loop Variable Bit Rate (OL-VBR), all encoder parameters are simply kept fixed at all times. The motivation behind this scheme is to presumably provide a more consistent video quality compared to CBR encoding. In this report, we characterize the traffic and quality for the CBR and OL-VBR schemes by using several video sequences of different spatial and temporal characteristics, encoded using the H.261, MPEG, and motion-JPEG standards. We investigate the effect of the controller parameters (i.e., for CBR, target bit rate and rate control buffer size, and for OL-VBR, the fixed quantizer scale) and video content on the resulting traffic and quality. We show that with the CBR and OL-VBR schemes, the encoder control parameters can be chosen so as to achieve or exceed a given quality objective at all times; however, this can only be done by producing more bits than needed during some of the scenes. In order to produce only as many bits as needed to achieve a given quality objective, we propose a video encoder control scheme which maintains the quality of the encoded video at a constant level, referred to as Constant Quality VBR (CQ-VBR). This scheme is based on a quantitative video quality metric which is used in a feedback control mechanism to adjust the encoder parameters. We determine the appropriate feedback functions for the H.261, MPEG, and motion-JPEG standards. We show that this scheme is indeed able to achieve a constant quality at all times; however, the resulting traffic occasionally contains bursts of relatively high-magnitude (5-10 times the average), but short duration (5-15 frames). We then introduce a modification to this s

System and method for displaying a video menu

Abstract: An interactive video menu system provides an economical method for the storage, transmission, and reception of data necessary for interactive video sessions, which allows high-resolution images to be broadcast to end users along with all the control information necessary to display and navigate through these images. A simple interpretive script is run on the end user's device which traps the broadcast information and allows rapid response time and control of the interactive session without requiring expensive high-bandwidth facilities. Buffer equalized coding is used so that still, picture-in-a-still; and moving video images can be compressed at rates below those typically used with the MPEG-2 standard and continuously transmitted as video backgrounds in a seamless loop saving bandwidth without degradation in video quality. Data that instructs the end-user device how to display the video backgrounds and what foreground text to overlay on the video backgrounds is broadcast simultaneously in the bit stream This creates the appearance of a dedicated connection to the server while minimizing bandwidth and equipment cost and complexity.

Study of MPEG-2 coding performance based on a perceptual quality metric

Abstract: Study of MPEG-2 Co ding Performance based on a PerceptualQuality MetricAndrea Basso* **_Ismail Dalgc*Fouad A. Tobagi* andChristian J. van den Branden Lambrecht**** Department of Electrical Engineering Stanford University** Telecommunication Laboratory Swiss Federal Institute of Tchnology*** Signal Processing Laboratory Swiss Federal Institute of TchnologyAbstractIn this paper some wel l known quality metrics suchas PSNR and the metric developed at Institute forTelecommunication Sciences (ITS) arereviewed.Their shortcomings in measuring quality of co-ded videocompared to subjective tests arepointedout. Then, a new video quality metric cal led Mo-ving Picture Quality Metric (MPQM) is presented.This metric models the human visual system andmatches correctly subjective evaluations. Compa-rative results in the case of constant bit rate (CBR)MPEG-2 codedsequences arepresented, showingthe superiority of MPQM over ITS and PSNR.1Intro ductionThe interest in multi-media applications - with astrong emphasis on video issues - is growing tre-mendously.Video assessment is a fundamentaland still not suciently explored asp ect of the cur-rent research on video co ding.Visual ob jectivemetrics that are coherent with quality as p erce-ived byhuman observers are b eginning to emergeonly recently.Furthermore very recently the con-cept of constant-quality video enco ding has b eenintro duced in [1] and further develop ed in [2].The motivation of this work is to determine theright kind of quality metric for devising a constant-qualityvariable bit rate (CQ-VBR) video enco dingscheme for MPEG-2 in view of an evaluation itsp erformances over ATM.In this pap er some well known quality metricsfor video such as the well known and widelyused Peak Signal to Noise Ratio (PSNR) and themetric develop ed at Institute for Telecommunica-its prop ertThis work was supp orted in part by NSF under grantNCR-9016032, and byPaci c Bell.tion Science (ITS) are reviewed. Then, a new vi-deo quality metric called Moving Picture QualityMetric (MPQM) is discussed. That metric is ba-sed on a mo del of the early stages of the human vi-sual system and it matches sub jectiveevaluationscorrectly. Results for the considered metrics areshown for constant bit rate (CBR) MPEG-2 co-ded sequences.The pap er is organized as follows. Sec. 2 over-views the literature on video quality assessmentand measurement. Sec. 3 illustrates the inadequ-acy of PSNR metric for video quality assessmentby means of a simple example. Sec.4 presentsthe ITS video quality metric and its p erformanceon MPEG-2 co ded video.Sec.5 discusses theMPQM. Some conclusive remarks end the pap er.2Stateoftheartinvideoquality assessment and me-asurement2.1First DevelopmentsVideo quality assessment plays a fundamental rolein the development of new and existing video co-ding algorithms.The interest for image qualityevaluation has b een strong since the sixties. Se-veral image quality metrics hae b een develop ed,such as the Strehl measure [3], based on the degra-dation to which an image is sub ject to, wheneverit passes di erent real optical systems compared tothe ideal case. Attempts with bivariate metrics ofimage qualityhave b een done in particular duringthe seventies. The reader is referred to [4] for areview.The mean square error has b een retained fory of b eing easily analytically tractable.Wilder [5] did a rather complete evaluation of dif-1

Edge-oriented intra-field/inter-field interpolation filter for improved quality video appliances

Abstract: An interpolation filter for video signals includes four circuits to improve video quality in both intra-field and inter-field modes. The interpolation filter is configured to interpolate according to the direction of an image edge. The interpolation filter is also configured to interpolate in a prescribed spatial direction when no image edges can be univocally determined. The first circuit detects an image edge of discrete image elements to generate a first signal. The second circuit uses output from the first circuit to generate a first signal corresponding to an average of the discrete image elements along a direction of the image edge. The third circuit uses output from the first circuit to detect a texture image area wherein an image edge cannot be univocally determined and for generating a second signal depending on a degree of existence of the image edge. The fourth circuit is supplied by the first signal, the second signal and a third signal. The fourth circuit generates an output signal obtained by combining the first signal with the third signal in a proportion dependent upon the second signal. Additionally, the fourth circuit is configured for multiplexing to selectively couple the third signal to a fourth signal, corresponding to an average of the discrete image elements along a prescribed direction, or to a fifth signal corresponding to a previously received image element value.

Program Verification for Cable Television at a Consumer Location

Abstract: Verifying that a correct program is being received and displayed on a television set of a consumer. In addition, video quality is checked to assure that transmission has not degraded the video quality. When the consumer requests a program by transmission of a message via a controller in a set top box to a system computer controlling a cable television system, the system computer sends the necessary commands to cause the requested program to be communicated to the consumer site and also transmits to the controller in the set top box a start time of the requested program and information defining the initial video content of that program. At the start time, the controller verifies that the initial video content is being received and that the consumer has the set top box correctly tuned. The controller uses a frame grabber circuit at the consumer site to grab the initial portion of the program and then to analyze the stored portion with respect to the initial video content. If the stored portion is not the same as the initial video content, the controller transmits an error message to the system computer. In response to the error message, the system computer corrects the switching or transmission problem so that the correct program is being sent to the consumer site. The system computer then verifies that the correct program is being received.

Method and system for integrating video and data transfers in a multimedia session

Abstract: A method and system for integrating occasional user-initiated data transfers with a generally continuous video transmission in a multimedia communications session includes enabling a party of the session to select at least two levels of video quality of service for the session. A first level is selected for time segments in which the user-initiated data transfers are active. A second level of video QoS is selected for time segments having user-initiated data transfers. Connectivity for the session is established based upon the first level. However, upon initiation of a data transfer, the video transmission requirements are switched to requirements based upon the second level of video quality of service. Present-time quality of service is monitored to determine whether the data transfer should be regulated so as to ensure that the present-time video quality of service remains at or above the second selected level. The method and system allow a user to determine what level, if any, of degradation is permissible during the data transfers.

Objective and Subjective Measures of MPEG Video Quality

Abstract: Presents an in-depth analysis and discussion of the results from applying the ANSI T1.801.03-1996 objective video quality metrics to subjectively rated MPEG-1 and MPEG-2 video test scenes. The objective metrics presented in ANSI T1.801.03-1996 (American National Standard for Telecommunications - Digital Transport of One-Way Video Signals - Parameters for Objective Performance Assessment) were able to account for 90% of the subjective information that could be captured considering the level of measurement error present in the subjective and objective data sets. By contrast, peak signal to noise ratio (PSNR), a traditional objective metric, was only able to account for 21% of the subjective information.

The Influence of Impairments from Digital Compression of Video Signal on Perceived Picture Quality

Abstract: Publisher Summary Generally, the performance of a video compression system can be evaluated objectively or subjectively. The objective methods are based on computable distortion measure such as mean squared error or signal to noise ratio (SNR). Objective measurements have limited effectiveness in predicting the quality of compressed images as seen by the observers. On the other hand, subjective assessment is geared directly toward properties of the human visual system. Subjective assessments are controlled psycho-physical experiments that are designed to find out how the observers would judge picture quality. It is the reason why subjective assessment is the most effective method for determining the influence of video compression method on picture quality. Picture impairments in digital video systems are different from those that occur in analogue systems and depend on the methods of coding and redundancy reduction employed. With the increasing applications of moving picture experts group (MPEG) coding, the assessment of MPEG coding impairments becomes very important. The aim of this chapter is to present results of picture quality assessment in relation to impairments from MPEG-1 coding for workstation and personal computer applications where pictures are displayed within a window on a monitor.

Quadtree-based reconfigurable cordless videophone systems

Abstract: Arbitrarily programmable, but fixed-rate quadtree (QT) decomposed, parametrically enhanced videophone codecs using quarter common intermediate format (QCIF) video sequences are proposed as a direct replacement for mobile radio voice codecs in second generation systems, such as the Pan-European GSM, the American IS-54 and IS-95, as well as the Japanese systems. The corresponding bit rates are 13, 8, 9.6 and 6.7 kb/s, respectively. As an example, the proposed 11.36 kb/s prototype Codec 1 and the 11 kb/s Codec 2 are embedded in the adaptively reconfigurable wireless videophone systems 1-4 featured in a table and their video quality, bit rate, robustness, and complexity issues are investigated. Coherent reconfigurable 16 or four-level pilot symbol assisted quadrature amplitude modulation (PSAQAM) is used and the system's robustness is improved by a combination of diversity and automatic repeat request (ARQ) techniques. When using a bandwidth of 200 kHz, as in the Pan-European GSM mobile radio system, the number of videophone users supported varies between three and 16, while the minimum required channel signal to noise ratio over Gaussian and Rayleigh channels is in excess of 6 and 8 dB, respectively, assuming a noise-limited, rather than interference-limited scenario. The salient system features are also summarized in a table.

Apparatus and method for a programmable video motion estimator

Abstract: A programmable motion estimator having a memory and processing element array that implement a dual addressing scheme and a block rotating scheme that work together to perform block difference calculations required in video encoder subsystems to provide motion estimation with less processing power without comprising video quality.

Joint encoder and channel rate control of VBR video over ATM networks

Abstract: Rate control is considered as an important issue in video coding, since it significantly affects video quality. In this paper, we will discuss joint encoder and channel rate control for variable bit-rate (VBR) video over packet-switched Asynchronous Transfer Mode (ATM) networks. Since a variable bit-rate traffic is allowed in such networks, an open-loop encoder without rate control can generate consistent-quality video. But in order to improve statistical multiplexing gain (SMG), an encoder buffer is essential to smooth highly variable video bitstream. Due to the finite buffer size, some forms of encoder rate control have to be enforced and consequently, video quality varies. We argue that a rate control scheme has to balance both issues of consistent video quality on the encoder side and bitstream smoothness for SMG on the network side. We present a joint encoder and channel rate control algorithm for ATM networks, with leaky buckets as open-loop source flow control models. The encoder rate control is separated into a sustainable-rate control and a unidirectional instantaneous-rate control. It can improve the problem of leaky bucket saturation exhibited in previous works. Experimental results with MPEG video will be presented. The results verify our analysis and show the effectiveness of the proposed algorithm.

Multilevel video coding and distribution architectures for emerging broadband digital networks

Abstract: There is a renewed interest in video-based communications. The expected proliferation of various video communication applications has in turn resulted in a need for scalable and efficient digital video encoding schemes which would enable the dissemination of video signals at differing spatial resolution, depending on end-user needs and limitations. Also, along with this is the need for a universal broadband in which the same transmitted signal is efficiently distributed to various end-user applications, allowing them to communicate at differing grades of video quality. As a first step, this paper presents an efficient and scalable video coding scheme. The scheme is capable of encoding and decoding video signals in a hierarchical, multilayer fashion to provide video at differing quality grades, e.g., NTSC, extended quality (EQTV), high definition (HDTV). Since the lower levels in such a scheme can be encoded independently of the upper levels, compatibility with some of the standard codecs can be directly imposed. In addition, strategies to control quantization noise for independent transmission by means of residual layering are also discussed. This paper also discusses the utilization of this coding scheme to enable efficient bit rate sharing and robust distribution of video communication signals at three distinct quality grades in multicasting, as well as multipoint communication applications for multiparty video-conferencing. Two special distribution architectures are considered which involve the use of SMDS and ATM as the transport and delivery vehicles.

Storage and retrieval of compressed video

Abstract: This work consists of three main parts. In the first part, we consider various aspects of video compression. We exploit motion in real video sequences within the context of subband coding by using two-dimensional nonseparable checker filters and adaptive one-dimensional two-tap temporal filters. Since the latter technique is shown to be more feasible for actual video encoding, we combine it with a multi-rate quantization strategy to form a scalable video subband encoder. Finally, we refine and optimize one aspect of our multi-rate quantization strategy known as significance map coding. The optimized map coding is integrated into a highly scalable subband codec and shown to increase the overall encoding and decoding speed by up to a factor of two, at a cost of one to two dB of decoded video quality. The second part of this work explores the issue of Variable Bit Rate (VBR) video storage. The fundamental issue in VBR data placement is the choice of blocks that are of constant playback duration or constant size. We call the first option constant time length (CTL) and the second constant data length (CDL); in addition, we consider a third hybrid option that stores CDL blocks but retrieves a variable number of blocks per user in each service round. By considering total disk and buffer cost to be our final quality metric, we show CTL and hybrid schemes to be cost-effective, but CDL is too expensive for long video sequences. We also address the issue of VBR admission control policies by comparing statistical and deterministic techniques. Statistical admission control uses statistics of the stored data to ensure that the probability of disk overload does not exceed a prespecified threshold. Deterministic control uses the actual stored video bit traces to regulate the number of admitted users. We show that one form of deterministic admission control, data-limit, is feasible and results in a reduction in cost and probability of overload. The final part addresses the issue of scalable video storage. To this end, we present the principle of constant frame grouping, placing an equal number of frames in the same rate layer together in each read unit. In comparison to other strategies, we find that constant frame grouping allows the video server to service more simultaneous users at a variety of user distributions. We then apply constant frame grouping to VBR video data storage using the CTL and hybrid data placement techniques. This allows the video server to provide graceful degradation in times of disk overload and also reduces the delay arising from the use of VCR functions in data-limit admission control. We extend our strategies to multiple disks and show that our interleaving technique serves more users and has lower delay than a comparable striped system.

Objective picture quality scale for video coding

Abstract: To design the image communication system including human visual system systematically, the objective quality estimation method of the picture based on the model of the human vision is necessary. We develop the objective picture quality scale (PQSvideo) for video coding considering the relation between the physical distortion factors and the psychological picture estimation factors. The obtained cross correlation coefficient between the PQSvideo and the mean opinion score (MOS), becomes 0.978.

Video encoder architecture for MPEG2 real time encoding

Abstract: A video encoder architecture for encoding digital video signals based on the MPEG2 video standard up to the slice level is described. A function specific architecture is implemented to increase the coding efficiency and reduce the silicon area for real time encoding. A hierarchical control concept is adopted and a three-stage pipeline encoding method is used in the macroblock coding to increase the flexibility of the encoding flow and reduce the design effort. Most of the computing power for the MPEG2 encoding algorithm is utilized in motion estimation, so a separate motion estimation module is used as a coprocessor. The motion estimation algorithm adopted is a full search with the search window in the range between +47 and -48 pels in the horizontal direction and between +15 and -16 pels in the vertical direction. Simulations on several video sequences with different target bit rates are evaluated. The results show that our implementation can achieve a video quality comparable to other off-line software simulation programs using exhaustive searches.

Video compression coding apparatus and video compression recording/playback apparatus

Abstract: The object of the present invention is to provide a video compression coding apparatus which, in the case where a code quantity variation allows a greater margin, can compress video data while suppressing any degradation of a video quality First, input video data, after being transformed by a DCT section to a DCT coefficient, is quantized, by a quantizing section, with a quantization level designated with quantization control data This quantized data is input to a variable length coding section where it is compression-coded in a block unit corresponding to a field or frame A code quantity detecting section detects a code quantity of this coded data and delivers a result of detection to a quantization control section The quantization control section has a given coding quantity-quantization level control characteristic representing a relation, to the quantization level, of the code quantity which obtains an average code quantity of initially input video data The quantization control section determines a quantization level of the next block on the basis of the control characteristic and code quantity information from the code quantity detecting section and generates corresponding quantization control data

Optimal bit allocation for video coding under multiple constraints

Abstract: We consider optimal encoding of video sequences (for ATM networks) under buffer and channel constraints. For independent coding, we develop an algorithm which employs multiple Lagrange multipliers to find the constrained optimal bit allocation, Simulation results are presented. We also compare the coded video quality and other characteristics of variable bit-rate and constant bit-rate transmission.

Cell loss properties for multiplexing of MPEG video sources considering picture coding types in ATM networks

Abstract: In MPEG coding, there are three types of encoded pictures. Since these picture coding types have different importance of data content, the cell loss of each picture coding type affects the video quality differently in MPEG video transmission through ATM networks. This paper analyzed the per-session cell loss properties of MPEG video traffic in an ATM switching node in both the steady-state case and the transient case considering each picture type. In the analysis, a 3-state Markov modulated Bernoulli process (MMBP) is proposed as a traffic model for MPEG video which is tractable analytically. Numerical results revealed the influence of the picture transmission pattern on the cell loss properties of each picture coding type.

Region-based wavelet compression for very low bit rate video coding

Abstract: We present a region-based wavelet compression method for encoding video sequences at very low bit rates suitable for videophone applications. By selectively coding texture information in the regions of interest, we avoid spending bits in the unimportant regions and improve video quality. The embedded zerotree wavelet algorithm is extended to efficiently represent the wavelet coefficients within the regions of interest while exploiting redundancy between subbands. The locations of the regions of interest are selected during the motion estimation process and are transmitted as part of the macroblock type. This technique can provide better quality compared to the new H.263 videophone compression standard. This technique was also incorporated in a more general object-based compression scheme which obtained high scores during the recent MPEG-4 subjective quality evaluations.

4:1 checkerboard algorithm for motion estimation

Abstract: Motion-compensated prediction is a key technique for achieving high compression performance for a video sequence. Exhaustive search produces the best predictor block but requires intensive computation and expensive hardware. This paper presents a 4:1 checker-board algorithm that reduces the computational complexity of exhaustive search by a factor of 8 while maintaining similar video quality. The algorithm subsamples block pixels by four to one, wand subsamples search locations by two to one. The resulting architecture is simple and scalable, and is suitable for real-time encoding.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Motion rendition quality metric for MPEG coded video

Abstract: This article addresses duality assessment of motion rendition in digital video coding. Motion estimation and compensation are critical modules in video coders. A computational metric, based on a spatio-temporal model of the human visual system and of human motion sensing, is proposed and used to evaluate MPEG-2 compressed video. The metric is able to assess the quality of motion rendition and exhibits a good correlation with subjective data.

Power-controlled H.263-based wireless videophone performance in interference-limited scenarios

Abstract: An H.263-based video transceiver is contrived, which maintains a near-constant bitrate and due to the proposed packetisation and packet dropping regime it provides near-unimpaired video quality for frame error rates up to 5%. The target frame error rate is maintained by invoking a novel power-control technique.