Smoooth Streaming over wireless NetworksSreya ChakrabortyInterim ReportEE-5359Abstract: Smooth streaming is a serious problem since bandwidth is a natural resource and it islimited. In this paper the implications of video traffic smoothing on the numbers of statisticallymultiplexed H.264 SVC,H.264/AVC, and MPEG-4 Part 2 streams, the bandwidth requirementsfor streaming, and the introduced delay are examined. SVC enables the transmission anddecoding of partial bit streams to provide video services with lower temporal or spatialresolutions or reduced fidelity while retaining a reconstruction quality that is high relative to therate of partial bit streams. Here two algorithms are proposed for compressive multimedia streamsto considerate level. Introduction: Smooth streaming is a challenge in areas where bandwidth is low or limited. Inmost of the cases for streaming video and audio data UDP was found useful over TCP, since TCPintroduces various delays. It also waits for the receipt of acknowledgement causing delay in theframe arrival. The loss of data is acceptable to certain extent but not the delay caused. Modernvideo transmission and storage are based on RTP/IP for real time services. Most RTP/IP accessnetworks are typically characterized by a wide range of connection qualities and receivingdevices. The varying connection quality is due to adaptive resource sharing mechanisms of thesenetworks. Traditional digital video transmission and storage systems are based on H.222.0,H.320 [7] for broadcasting services over satellite, cable, and terrestrial transmission channels, forDVD storage and for conversational video conferencing services. International video codingstandards H.262, H.263 and MPEG-4 already include several tools by which the most importantscalability modes can be supported. But the characteristics of traditional video transmissionsystems and the quality scalability features came with a significant loss in coding efficiency aswell as a large increase in decoder complexity. Simulcast provides similar functionalities as ascalable bit stream.Scalable video coding extension of the H.264/AVC with its hierarchical B-frames compressessingle layer video. H.264/AVC and H.264 SVC video encoding are expected to be widelyadopted for wired and wireless network video transport due to their increased compressionefficiency compared to MPEG-4 and their widespread inclusion in application standards. Thecompression efficiency of a video codec is generally characterized with a rate distortion curve[2]that shows the bit rate of the compressed video stream as a function of the video quality(distortion), which is typically measured in terms of the Peak Signal to Noise Ratio (PSNR). Fora given video quality, the lower the compressed bitrate, the more efficient is the compression.The improvements in rate-distortion (RD) compression efficiency with H.264 SVC andH.264/AVC come at the expense of significantly increased variabilities of the encoded framesizes (in bits). 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 thanMPEG–4 Part 2. Since the traffic characteristics of encoded video have a significant impact onits network transport, the bit rate-distortion and bit rate variability-distortion performance ofsingle-layer video traffic of the H.264/AVC codec and SVC extension using long CIF resolutionvideos is examined. The traffic characteristics of the hierarchical B frames (SVC) versusclassical B frames is compared. In addition, we examine the impact of frame size smoothing onthe video traffic to mitigate the effect of bit rate variabilities. Compared to MPEG–4 Part 2, theH.264/AVC codec and SVC extension achieve lower average bit rates at the expense ofsignificantly increased traffic variabilities that remain at a high level even with smoothing.Through simulations we investigate the implications of this increase in rate variability on (i)frame losses when transmitting a single video, and (ii) on the number of supported video streamsin a bufferless statistical multiplexing scenario with restricted link capacity and information loss.In general, video can be encoded (i) with fixed quantization scales, which results in nearlyconstant 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 ofvariable video quality. In order to examine the fundamental traffic characteristics of theH.264/AVC video coding standard, which does not specify a normative rate control mechanism,primarily on encodings with fixed quantization scales is focused. An additional motivation forthe focus on variable bit rate video encoded with fixed quantization scales is that the variable bitrate streams allow for statistical multiplexing gains that have the potential to improve theefficiency of video transport over communication networks. The development of video networktransport mechanisms that meet the strict playout deadlines of the video frames and efficientlyaccommodate the variability of the video traffic is a challenging problem. A wide array of videotransport mechanisms has been developed and evaluated, based primarily on the characteristicsof MPEG–2 and MPEG–4 Part 2 encoded video. The widespread adoption of the newH.264/AVC video standard necessitates the careful study of the traffic characteristics of videocoded with the new H.264/AVC codec and its extensions. Therefore, it is necessary to examinethe new video encoder’s statistical characteristics and compression performance from acommunication network perspective. We study the Main profile of the H.264/AVC encoder usinglong Common Intermediate Format (CIF) 352x288 pixel resolution sequences. Our study of thenewest H.264 SVC extension analyzes single-layer (non-scalable) video traffic characteristics oflong CIF videos, i.e., although the H.264 SVC single-layer encoding supports temporalscalability, we group the individual temporal layers and consider the
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