Topic
Video quality
About: Video quality is a research topic. Over the lifetime, 13143 publications have been published within this topic receiving 178307 citations.
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TL;DR: Basic characteristics of variable-rate video coders applied to asynchronous transfer mode (ATM) transmission are described and burstiness of video information is evaluated for conference-type scenes using various coding algorithms.
Abstract: Basic characteristics of variable-rate video coders applied to asynchronous transfer mode (ATM) transmission are described Burstiness of video information is evaluated for conference-type scenes using various coding algorithms Three measures (distribution, autocorrelation, and coefficient of variation) are introduced to evaluate burstiness Video sources are modeled and characterized by the autoregressive process and coefficient of variation Video quality improvement achieved with variable rate transmission is evaluated using signal-to-noise ratio (SNR) and subjective ratings An improvement of 5-10 dB in temporal SNR and 1 rank in mean opinion score are reported >
228 citations
TL;DR: In this article, a viewport-adaptive 360-degree video streaming system is proposed to reduce the bandwidth waste, while still providing an immersive experience, by preparing multiple video representations, which differ not only by their bit-rate, but also by the qualities of different scene regions.
Abstract: The delivery and display of 360-degree videos on Head-Mounted Displays (HMDs) presents many technical challenges. 360-degree videos are ultra high resolution spherical videos, which contain an omnidirectional view of the scene. However only a portion of this scene is displayed on the HMD. Moreover, HMD need to respond in 10 ms to head movements, which prevents the server to send only the displayed video part based on client feedback. To reduce the bandwidth waste, while still providing an immersive experience, a viewport-adaptive 360-degree video streaming system is proposed. The server prepares multiple video representations, which differ not only by their bit-rate, but also by the qualities of different scene regions. The client chooses a representation for the next segment such that its bit-rate fits the available throughput and a full quality region matches its viewing. We investigate the impact of various spherical-to-plane projections and quality arrangements on the video quality displayed to the user, showing that the cube map layout offers the best quality for the given bit-rate budget. An evaluation with a dataset of users navigating 360-degree videos demonstrates that segments need to be short enough to enable frequent view switches.
228 citations
TL;DR: This paper compares the performance of these techniques (excluding temporal scalability) under various loss rates using realistic length material and discusses their relative merits.
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.
227 citations
19 Sep 2011
TL;DR: SoftCast is presented, a cross-layer design for mobile video that improves the average video quality for multicast users by 5.5dB, eliminates video glitches caused by mobility, and increases robustness to packet loss by an order of magnitude.
Abstract: Today's mobile video suffers from two limitations: 1) it cannot reduce bandwidth consumption by leveraging wireless broadcast to multicast popular content to interested receivers, and 2) it lacks robustness to wireless interference and errors. This paper presents SoftCast, a cross-layer design for mobile video that addresses both limitations. To do so, SoftCast changes the network stack to act like a linear transform. As a result, the transmitted video signal becomes linearly related to the pixels' luminance. Thus, when noise perturbs the transmitted signal samples, the perturbation naturally translates into approximation in the original video pixels. This enables a video source to multicast a single stream that each receiver decodes to a video quality commensurate with its channel quality. It also increases robustness to interference and errors which now reduce the sharpness of the received pixels but do not cause the video to glitch or stall. We have implemented SoftCast and evaluated it in a testbed of software radios. Our results show that it improves the average video quality for multicast users by 5.5dB, eliminates video glitches caused by mobility, and increases robustness to packet loss by an order of magnitude.
227 citations
TL;DR: New methods of performing selective encryption and spatial/frequency shuffling of compressed digital content that maintain syntax compliance after content has been secured are introduced.
Abstract: We introduce new methods of performing selective encryption and spatial/frequency shuffling of compressed digital content that maintain syntax compliance after content has been secured. The tools described have been proposed to the MPEG-4 Intellectual Property Management and Protection (IPMP) standardization group and have been adopted into the MPEG-4 IPMP Final Proposed Draft Amendment (FPDAM). We describe the application of the new methods to the protection of MPEG-4 video content in the wireless environment, and illustrate how they are used to leverage established encryption algorithms for the protection of only the information fields in the bitstream that are critical to the reconstructed video quality, while maintaining compliance to the syntax of MPEG-4 video, and thereby reduces the amount of data to be encrypted and guarantees the inheritance of many of the good properties of the unprotected bitstreams that have been carefully studied and built, such as error resiliency and network friendliness. The encrypted content bitstream works with many existing random access, network bandwidth adaptation, and error control techniques that have been developed for standard-compliant compressed video, thus making it especially suitable for wireless multimedia applications. Standard compliance also allows subsequent signal processing techniques to be applied to the encrypted bitstream.
226 citations