Showing papers on "Video quality published in 1993"

Objective video quality assessment system based on human perception

Abstract: The Institute for Telecommunication Sciences (ITS) has developed an objective video quality assessment system that emulates human perception. The system returns results that agree closely with quality judgements made by a large panel of viewers. Such a system is valuable because it provides broadcasters, video engineers and standards organizations with the capability for making meaningful video quality evaluations without convening viewer panels. The issue is timely because compressed digital video systems present new quality measurement questions that are largely unanswered. The perception-based system was developed and tested for a broad range of scenes and video technologies. The 36 test scenes contained widely varying amounts of spatial and temporal information. The 27 impairments included digital video compression systems operating at line rates from 56 kbits/sec to 45 Mbits/sec with controlled error rates, NTSC encode/decode cycles, VHS and S-VHS record/play cycles, and VHF transmission. Subjective viewer ratings of the video quality were gathered in the ITS subjective viewing laboratory that conforms to CCIR Recommendation 500-3. Objective measures of video quality were extracted from the digitally sampled video. These objective measurements are designed to quantify the spatial and temporal distortions perceived by the viewer. This paper presents the following: a detailed description of several of the best ITS objective measurements, a perception-based model that predicts subjective ratings from these objective measurements, and a demonstration of the correlation between the model's predictions and viewer panel ratings. A personal computer-based system is being developed that will implement these objective video quality measurements in real time. These video quality measures are being considered for inclusion in the Digital Video Teleconferencing Performance Standard by the American National Standards Institute (ANSI) Accredited Standards Committee T1, Working Group T1A1.5.

Real-time software-based video coder for multimedia communication systems

Abstract: A novel software-based video compression algorithm, the Popular Video Coder (PVC), is presented in this paper, and a video phone system, the Popular Phone, is also implemented based on the PVC. The PVC simplifies the traditional video coder by removing the transform and the motion estimation parts and modifies the quantizer and entropy coder. Two novel coding algorithms, the adaptive quantizer and the modified windowed Huffman-like coder, are used in the PVC to encode the video data with a quality picture at a high compression ratio. The video quality of the proposed coder is as good as that of the MPEG coder when the input is a low-resolution and slow-motion video, and the computational complexity of the PVC is much lower than that of the Motion Picture Expert Group (MPEG). Since no compression hardware is needed for the PVC to encode and decode video data, the cost and complexity of developing multimedia applications, such as video phone and multimedia e-mail systems, can be greatly reduced. Furthermore, some networking issues, such as error control and flow control, are discussed in connection with applying the PVC to implement the Popular Phone.

Perception-based video quality measurement system

Abstract: A method and apparatus for objectively measuring the image quality of a destination video signal generates measurement parameters that are indicative of human image quality perceptions. Subjective human test panel results are generated for a variety of test scenes and types of image impairment. Objective test results are also generated by the apparatus of the present invention for the variety of test scenes and image impairments. A statistical analysis means statistically analyzes the subjective and objective test results to determine operation of the apparatus. Accordingly, when the apparatus extracts test frames from the actual source and destination video signals and compares them, image quality parameters are output by the apparatus which are based on human image quality perceptions.

The Influence of Video Image Size and Resolution on Viewing-Distance Preferences

Abstract: This article describes five experiments that were conducted to evaluate viewing-distance preferences as a function of video image size and resolution. Viewing-distance preferences are a key design parameter for work involving human factors in video teleconferencing, distance learning, and other multimedia applications. In addition, viewing-distance preferences have been treated as a subjective measure of image quality and used in ongoing discussions of proposed standards for high-definition television (HDTV). Based on previous literature, it was hypothesized that the ratio of viewing-distance preferences to image height would be a constant, would vary based on image resolution, and would average around 7 for standard NTSC video (with 525 scan lines of resolution). Contrary to the predictions, the data showed that the ratio decreases as image size increases, and that the ratios are relatively uninfluenced by image resolution. The data for the five experiments were combined to generate a guideline for estimating viewing-distance preferences across a wide range of video image sizes.

Modeling and subjective assessment of cell discard in ATM video

Abstract: Measurements of subjective picture impairment as a function of network loading in a simulated ATM network are reported. The simulation indicated that cells tend to be discarded in bursts, the frequency and severity of which can be related to the loading by a threshold model. The effect of the discards on broadcast-style video, coded using a single-layer H.261-type method, was found to be a function of scene content and movement at the instant of occurrence. If the visibility of cell discards is maintained at or below threshold in worst-case scenes, the study indicated that network loadings around 55% for a multiplex of 16 video sources and around 70% for a multiplex of 48 video sources are achievable. >

Psycho-visual based distortion measures for monochrome image and video compression

Abstract: Describes quantitative distortion measures for compressed monochrome image and video based on a psycho-visual model. The model follows the human vision perception in that the distortion as perceived by a human viewer is dominated by the compression error uncorrelated with the local features of the original image and for a video sequence the distortion is perceived from two sources, the still areas and the motion areas of a video frame. The authors have performed subjective tests to obtain ranking results for compressed images and video sequences which were compressed using different compression algorithms and compared the results with the rankings obtained using their distortion measure and other existing mean-square error based measures. They have found that their distortion measure's ranking matches the subjective ranking accurately whereas the mean-square error and its variants performed poorly in matching the subjective ranking on an average. >

ATM transport and cell-loss concealment techniques for MPEG video

Abstract: Robust video compression and transport approaches are essential for operation over emerging ATM-based broadband ISDN and gigabit networks characterized by packet (cell) losses due to congestion. The same techniques also apply to delivery of digital TV and HDTV over cable, satellite, or terrestrial media in which high bit-error rates may occasionally be experienced. A specific cell-based MPEG video transport approach applicable to a variety of media is described for both one-tier and two-tier transmission alternatives. Decoder cell-loss concealment techniques supported by this transport format are introduced, and typical design issues are discussed. Simulation results showing end-to-end MPEG video quality are given illustrating the performance of the transport and concealment schemes under consideration for example channel scenarios. >

An objective technique for assessing video impairments

Abstract: An objective video impairment assessment technique that appears to quantify the perceptual impact of video impairments in an accurate way is presented. The development uses 132 impaired video sequences that cover a remarkably wide range of motion, detail, impairment type, and impairment level. The approach discussed in based on digital image processing operations performed on digitized original and impaired video sequences. Measurements that quantify perceptual video attributes in both the spatial and the temporal domains are extracted from the digitized video. These measurements are then used to compute a single score that quantifies the perceptual impact of the impairments present in the video sequence. This objective impairment score is well-correlated (r=.92) with impairment assessments made by human viewers. Thus, it can be used to augment, or possibly to replace, the expensive and time-consuming subjective viewing tests that are typically used to evaluate video coding and transmission techniques. >

Ghost canceler having a function of adaptively adjusting a signal level

Abstract: A ghost canceler having an adaptive signal level adjustment function includes an amplifier for amplifying an analog video signal provided to an analog-to-digital converter and a microprocessor for detecting the peak-to-peak value of the input video signal using a level difference between an input ghost cancellation reference signal contained within the analog video signal and a preset ghost cancellation reference signal and for determining an amplification coefficient using the detected peak-to-peak value. The analog-to-digital converter converts the amplified video signal to produce maximum bit resolution, which thereby permits ghost cancellation performance in the ghost canceler to be enhanced and prevent a loss in displayed video quality.

Rate- and resolution-scalable video and image compression with subband coding

Abstract: Proposes a full colour video compression strategy, based on 3D subband coding with camera pan compensation, to generate a single embedded bit stream supporting multiple decoder display formats and a wide, finely gradated range of bit rates. An experimental implementation of the algorithm produces a single bit stream, from which suitable subsets are extracted to be compatible with many useful decoder frame sizes and frame rates and to satisfy transmission bandwidth constraints ranging from several tens of kilobits per second to several megabits per second. Reconstructed video quality from any of these bit stream subsets is often found to exceed that obtained from an MPEG-1 implementation, operated with equivalent bit rate constraints, in both perceptual quality and mean squared error. In addition, when restricted to two dimensions, the algorithm produces some of the best results available in still image compression. >

Novel real-time software-based video coding algorithms

Abstract: Two novel real-time software-based video coders, the software-based moving picture coder (SBMPC) and the popular video coder (PVC), are proposed. SBMPC uses the modified block truncation code and multiresolution-in-time sampling techniques. PVC uses the adaptive quantizer and the modified windowed Huffman coder. Both the coding speed and the compression ratio are thus made much higher than those of traditional video coders. By using the proposed coders, video quality and coding speed are good and fast enough for practical video applications. Since no compression hardware is needed in the proposed video coders, the cost and complexity of developing multimedia applications can be greatly reduced. >

A Summary of Methods of Measurement for Objective Video Quality Parameters Based on the Sobel Filtered Image and the Motion Difference Image

Abstract: Summarizes detailed methods of measurement for objective video quality parameters based on the Sobel-filtered image and the motion difference image. This contribution was submitted to ANSI T1A1 prior to conducting the T1A1 subjective experiment (this experiment collected 625 mean opinion scores - i.e., 25 test scenes passed through 25 different video transmission systems that ranged in bit rate from 64 kb/sec to 45 Mb/sec). The video quality parameters presented here have demonstrated strong correlation to subjective evaluations of the video and can be used for in-service as well as out-of-service tests since low bit-rate features are extracted and compared from the input and corresponding output video images.

Stereoscopic video image display device

Abstract: PURPOSE:To devise the display device such that the luminance or the color temperature of a video image sensed actually by human eyes is seen the same when the video image is the same as a video image displayed on the display device regardless of the stereoscopic video image display device with/without an optical device CONSTITUTION:In the stereoscopic video image display device which has a video signal processing circuit 32 receiving selectively a usual video signal or a stereoscopic video signal and a display device 33 receiving selectively a usual video signal or a stereoscopic video signal from the video signal processing circuit 32 and displaying selectively a usual video image or a stereoscopic video image and in which stereoscopic vision is attained by viewing a stereoscopic video image displayed on the display device 33 through an optical device 9, the video signal processing circuit 32 is provided with video quality changeover means 44, 45 selecting the luminance or the color temperature depending whether the usual video signal or the stereoscopic video signal is received

Proposed Framework for Subjective Audiovisual Testing

Abstract: Working Group T1A15 is supporting ITU-T Study Group 12 in developing subjective audiovisual testing methods under Question 22/12 which addresses audiovisual quality in multimedia services A previous contribution from Bellcore, T1A15/93-104, describes three basic tests that can be used to examine how perceived audio quality and perceived video quality combine to create a perceived level of composite audiovisual quality These tests provide a logical and important first step toward understanding the components of subjective audiovisual quality The present contribution identifies two additional tests that could supplement the three basic tests by providing information about the interactions between perceived audio and video quality The five resulting tests are summarized in tabular form Key ideas from this contribution could be integrated with those presented in T1A15/93-104 to create a proposed US Contribution to ITU-T Study Group 12 When the authors presented this document at the meeting, they suggested that the McGurk Effect might be exploited to provide quality information and diagnostic information for audio-visual systems ITS staff created a videotape to demonstrate the McGurk Effect, and that tape was shown at the meeting A mov file (8 MB) and a avi file (27 MB) of that demonstration are available The McGurk Effect is most pronounced in the avi file, since the video in that file has been compressed less

FM-FDM optical CATV system employing demand access technology

Abstract: A demand-access optical CATV system using FM frequency multiplexing is developed. This system allows us to transmit 40 video signals including MUSE high vision signals over 40 km on a single-mode fiber trunk-line and can transmit arbitrary four video signals to subscribers at 10 km on subscribers' single-mode optical fibers. The feature of the present system is the possibility to fabricate an inexpensive hub by using a newly developed channel selector which combines single heterodyne and RF switch and also to make use of a cheap conventional DBS tuner at the subscribers' receiving terminal. For a trunkline, an optical modulation depth has to be carefully determined by considering an inter-modulation distortion. The present paper describes the degradation in effective CN ratio due to a white noise produced by the FM modulated third-order distortion and shows an optimum optical modulation depth for a given transmitting distance. Also, a system design is discussed for certain distances of a trunkline and a subscriber line. One can estimate using the present design the CN ratio at a subscriber terminal. The present system can provide the video quality of 4.5 (CN ratio 17.5 dB) for high vision.

Real-time software-based video coder for multimedia communication systems

Abstract: A novel software-based video compression algorithm, the Popular Video Coder (PVC), is presented in this paper, and a video phone system, the Popular Phone, is also implemented based on the PVC. The PVC simplifies the traditional video coder by removing the transform and the motion estimation parts and modifies the quantizer and entropy coder. Two novel coding algorithms, the adaptive quantizer and the modified windowed Huffman-like coder, are used in the PVC to encode the video data with a quality picture at a high compression ratio. The video quality of the proposed coder is as good as that of the MPEG coder when the input is a low-resolution and slow-motion video, and the computational complexity of the PVC is much lower than that of the Motion Picture Expert Group (MPEG). Since no compression hardware is needed for the PVC to encode and decode video data, the cost and complexity of developing multimedia applications, such as video phone and multimedia e-mail systems, can be greatly reduced. Furthermore, some networking issues, such as error control and flow control, are discussed in connection with applying the PVC to implement the Popular Phone.

Methods of Measurement for Two Objective Video Quality Parameters Based on the Fourier Transform

Abstract: Summarizes detailed methods of measurement for two objective video quality parameters based on the Fourier transform image. This contribution was submitted to ANSI T1A1 prior to conducting the T1A1 subjective experiment (this experiment collected 625 mean opinion scores - i.e., 25 test scenes passed through 25 different video transmission systems that ranged in bit rate from 64 kb/sec to 45 Mb/sec). The video quality parameters presented here have demonstrated strong correlation to subjective evaluations of the video and can be used for in-service as well as out-of-service tests since low bit-rate features are extracted and compared from the input and corresponding output video images.

Video signal band compression apparatus

Abstract: The apparatus is to increase a compression rate without degrading a video quality at the same time in the VCR recording or playing-back operation The system comprises: a frame memory (1) for storing digital video signals by a frame; a pattern generater to generate one of the two sampling patterns alternatively; a sub sampling part for subsampling the previously stored frame data; a pixel detector to detect the pixel position having the nearest distance from the sub-sampled pixel; an encoder (5) to encode the difference value; a multiplexer to thansmit the position informations and the unsubsampled record

Visual relevance of display image quality testing by photometric methods

Abstract: The two major international test methods for evaluation of the image quality of video display terminals are the ISO 9241-3 international standard and the MPR test. In this paper we make an attempt to compare the visual relevance of these two test methods.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.