Video quality

About: Video quality is a research topic. Over the lifetime, 13143 publications have been published within this topic receiving 178307 citations.

Viewer response to time-varying video quality

Abstract: Over the past several years we have investigated viewer response to temporal fluctuations in the quality of digital television pictures, which occur when video is coded into relatively low bit rates. Three phenomena of interest have been identified: (1) a forgiveness effect, (2) a recency effect, and (3) a negative-peak (duration-neglect); these are described and discussed in the paper. In collaboration with our partners in European projects MOSAIC and TAPESTRIES, we have developed a three-stage method of measuring time-variant quality, which has been accepted by the ITU-R. The first stage is a Single Stimulus Continuous Quality Evaluation (SSCQE) of instantaneous quality; the second a calibration stage to link SSCQE with conventional DSCQS, and the third stage a numerical procedure for relating continuous and overall quality. Some of the factors we have identified as being important in producing good overall quality judgements have relevance to the design of optimal coding strategies for digital television.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Programmable instrument for automatic measurement of compressed video quality

Abstract: A method of automatic measurement of compressed video quality superimposes special markings in the active video region of a subset of contiguous frames within a test video sequence. The special markings provide a temporal reference, a spatial reference, a gain/level reference, a measurement code, a test sequence identifier and/or a prior measurement value. The temporal reference is used by a programmable instrument to extract a processed frame from the test video sequence after compression encoding-decoding which is temporally aligned with a reference frame from the test video sequence. The spatial reference is used by the programmable instrument to spatially align the processed frame to the reference frame. The measurement code is used by the programmable instrument to select the appropriate measurement protocol from among a plurality of measurement protocols. In this way video quality measures for a compression encoding-decoding system are determined automatically as a function of the special markings within the test video sequence.

Quality assessment of asymmetric stereo video coding

Abstract: It is well known that the human visual system can perceive high frequencies in 3D, even if that information is present in only one of the views. Therefore, the best 3D stereo quality may be achieved by asymmetric coding where the reference (right) and auxiliary (left) views are coded at unequal PSNR. However, the questions of what should be the level of this asymmetry and whether asymmetry should be achieved by spatial resolution reduction or SNR (quality) reduction are open issues. Extensive subjective tests indicate that when the reference view is encoded at sufficiently high quality, the auxiliary view can be encoded above a tow-quality threshold without a noticeable degradation on the perceived stereo video quality. This low-quality threshold may depend on the 3D display; e.g., it is about 31 dB for a parallax barrier display and 33 dB for a polarized projection display. Subjective tests show that, above this PSNR threshold value, users prefer SNR reduction over spatial resolution reduction on both parallax barrier and polarized projection displays. It is also observed that, if the auxiliary view is encoded below this threshold value, symmetric coding starts to perform better than asymmetric coding in terms of perceived 3D video quality.

No-Reference Quality Metric for Degraded and Enhanced Video

Abstract: In this paper we present a no-reference objective quality metric (NROQM) that has resulted from extensive research on impairment metrics, image feature metrics, and subjective image quality in several projects in Philips Research, and participation in the ITU Video Quality Experts Group. The NROQM is aimed at requirements including video algorithm development, embedded monitoring and control of image quality, and evaluation of different types of display systems. NROQM is built from metrics for desirable and non-desirable image features (sharpness, contrast, noise, clipping, ringing, and blocking artifacts), and accounts for their individual and combined contributions to perceived image quality. We describe our heuristic, incremental approach to modeling quality and training the NROQM, and its advantages to deal with imperfect data and imperfect metrics. The results of training the NROQM using a large set of video sequences, which include degraded and enhanced video, show high correlation between objective and subjective scores, and the results of the first performance test show good objective-subjective correlations as well. We also discuss issues that require further research such as fully content-independent metrics, measuring over-enhanced video quality, and the role of temporal impairment metrics.

Multicast Resource Allocation Enhanced by Channel State Feedbacks for Multiple Scalable Video Coding Streams in LTE Networks

Abstract: The growing demand for mobile multicast services, such as Internet Protocol television (IPTV) and video streaming, requires effective radio resource management (RRM) to handle traffic with strict quality-of-service constraints over Long-Term Evolution (LTE) and beyond systems Special care is needed to limit system performance degradation when multiple multicast streams are simultaneously transmitted To this aim, this paper proposes an RRM policy based on a subgrouping technique for the delivery of scalable multicast video flows in a cell Our proposal enhances the legacy multicast transmission over LTE systems by exploiting multiuser diversity and the users' channel quality feedbacks Moreover, it is designed to take advantage of the frequency selectivity in the subgroup formation Simulation results demonstrate the effectiveness of the proposed scheme, which outperforms existing approaches from the literature It succeeds in achieving higher spectral efficiency and guaranteeing adequate video quality to all multicast receivers and improved quality to those with good channel conditions