Der Auwera1

698 IEEE TRANSACTIONS ON BROADCASTING, VOL. 54, NO. 3, SEPTEMBER 2008 Traffic and Quality Characterization of Single-Layer Video Streams Encoded with the H.264/MPEG-4 Advanced Video Coding Standard and Scalable Video Coding Extension Geert V an der Auwera, Prasanth T . David, and Martin Reisslein Abstract—The recently developed H.264/AVC video codec with Scalable Video Coding (SVC) extension, compresses non-scalable (single-layer) and scalable video significantly more efficiently than MPEG-4 Part 2. Since the traffic characteristics of encoded video have a significant impact on its network transport, we examine the bit rate-distortion and bit rate variability-distortion performance of single-layer video traffic of the H.264/AVC codec and SVC extension using long CIF resolution videos. We also compare the traffi c char acteristics of the hier arch icalB frame s (SVC)versus cl ass ica lB fra mes . In additi on, we examin e theimpac t of fra me siz e smoothing on the vi de o tr af fi c to mi ti gate the ef fe ct of bi t rate vari - abi lit ie s. We find that compar ed to MPEG-4 Par t 2, the H.2 64/ A VC code c and SVC exten sion ac hie ve lowe r ave rage bit rat es at th e expense of significantly increased traffic variabilities that remain at a high level even with smoothing. Through simulations we investi- gat e the imp lic ati ons of thi s inc re ase in rate var iab ili ty on (i) frame losses when transmitting a single video, and (ii) on a bufferless statistical multiplexing scenario with restricted link capacity and information loss. We find increased frame losses, and rate-distortion/rate-variability/encoding complexity tradeoffs. We conclude that solely assessing bit rate-distortion improvements of video encoder technologies is not sufficient to predict the performance in specific networked application scenarios. In dex T erms— Fr ame loss rati o, H. 264/ A VC, hi er a r- chical B frames, rate variability-distortion (VD), rate-distortion (RD), singl e-lay er vide o, stati stic al multi plexi ng, SVC, video quality, video traffic. I. INTRODUCTION W E ST UD Y th e vid eo tra f fi c ge ner ate d by th e H.264/ MPEG-4 Adv anc ed Vide o Cod ing sta nda rd [1] (H.264/AVC for brevity), also known as H.264/MPEG-4 Pa rt 10, and its rec ent ly sta nda rdizedScalab le Vide o Cod ing extension (SVC) [2], [3]. This new video technology is expected to ha ve a bro ad app lic ati on domain for wired and wir ele ss video transmission, and storage up to high definition (HD) resolution. Indications of the growing acceptance of H.264/AVC are its adoption in application standards and industry consortia Manuscript received July 8, 2007; revised March 10, 2008.First published June 20, 2008; last published August 20, 2008 (projected). This work was sup- ported in part by the National Science Foundation through Grant No. Career ANI-0133252 and Grant ANI-0136774. The authors are with the Department of Electrical Engineering, Arizona Sta te Uni ve rsi ty , Temp e, AZ 852 87-5706 USA (e-mail: gee rt.vander- [email protected]; [email protected]; [email protected]) Digital Object Identifier 10.1109/TBC.2008.2000422 specifications, such as DVB, A TSC, 3GPP, 3GPP2, MediaFLO, DMB, DVD Forum (HD-DVD), and Blu-Ray Disc Association (BD-ROM). At the same time, the introduction of IPTV over high speed access network links is ongoing, e.g., over Ethernet Passive Optical Networks (EPONs) or ADSL2+/VDSL2, and mobi le TV tech nolog ies are made widely ava ilab le. IPTV, mobile TV, and satellite TV are considered key applications that can make H.264/AVC the dominant video encoder in the broadcasting and consumer market. In general, video can be encoded (i) with fixed quantization scales, which results in nearly constant video quality at the expense of variable video traffic (bit rate), or (ii) with rate control, which adapts the quantization scales to keep the video bit rate nearly constant at the expense of variable video quality [4]. In order to examine the fundamental traffic characteristics of the H.264/AVC video coding standard, which does not specify a normative rate control mechanism, we focus primarily on en- cod ing s wit h fixe d qua nti zat ion sca les (an d pro vid e a bri ef stu dy of encodings with rate control in Section V-D). An additional motiv ation for the focus on variable bit rate video encoded with fixed quantization scales is that the variable bit rate streams allow for statistical multiplexing gains that have the potential to improve the efficiency of video transport over communication networks [4]. The development of video network transport mechanisms that meet the strict playout deadlines of the video frames and efficiently accommodate the variability of the video traffic is a challenging problem. A wide array of video transport mechanisms has been developed and evaluated, based primarily on the characteristics of MPEG-2 and MPEG-4 Part 2 encoded video [5], [6]. The widespread adoption of the new H.264/A VC video standard necessitates the careful study of the traffic characteristics of video coded with the new H.264/AVC codec and its extensions. Therefore, it is necessary to examine the new video encoder’s statistical characterist ics and compres- sion performance from a communication network perspective. We stu dy the Ma in pro file of the H.264/ A VC enc ode r usi ng lon g Common Int ermediate For mat (CIF) 352 288 pix el res olu tio n sequences. Our study of the newest H.264 SVC extension ana- lyzes single-layer (non-scalable) video traffic characteristics of long CIF videos, i.e., although the H.264 SVC single-layer encoding supports temporal scalability, we group the individual temporal layers and consider the aggregate stream. 0018-9316/$25.00 © 2008 IEEE

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