Smoooth Streaming over wireless Networks Sreya Chakraborty Interim Report EE 5359 Abstract Smooth streaming is a serious problem since bandwidth is a natural resource and it is limited In this paper the implications of video traffic smoothing on the numbers of statistically multiplexed H 264 SVC H 264 AVC and MPEG 4 Part 2 streams the bandwidth requirements for streaming and the introduced delay are examined SVC enables the transmission and decoding of partial bit streams to provide video services with lower temporal or spatial resolutions or reduced fidelity while retaining a reconstruction quality that is high relative to the rate of partial bit streams Here two algorithms are proposed for compressive multimedia streams to considerate level Introduction Smooth streaming is a challenge in areas where bandwidth is low or limited In most of the cases for streaming video and audio data UDP was found useful over TCP since TCP introduces various delays It also waits for the receipt of acknowledgement causing delay in the frame arrival The loss of data is acceptable to certain extent but not the delay caused Modern video transmission and storage are based on RTP IP for real time services Most RTP IP access networks are typically characterized by a wide range of connection qualities and receiving devices The varying connection quality is due to adaptive resource sharing mechanisms of these networks 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 for DVD storage and for conversational video conferencing services International video coding standards H 262 H 263 and MPEG 4 already include several tools by which the most important scalability modes can be supported But the characteristics of traditional video transmission systems and the quality scalability features came with a significant loss in coding efficiency as well as a large increase in decoder complexity Simulcast provides similar functionalities as a scalable bit stream Scalable video coding extension of the H 264 AVC with its hierarchical B frames compresses single layer video H 264 AVC and H 264 SVC video encoding are expected to be widely adopted for wired and wireless network video transport due to their increased compression efficiency compared to MPEG 4 and their widespread inclusion in application standards The compression 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 For a given video quality the lower the compressed bitrate the more ef cient is the compression The improvements in rate distortion RD compression ef ciency with H 264 SVC and H 264 AVC come at the expense of signi cantly increased variabilities of the encoded frame sizes 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 than MPEG 4 Part 2 Since the traffic characteristics of encoded video have a significant impact on its network transport 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 is examined The traffic characteristics of the hierarchical B frames SVC versus classical B frames is compared In addition we examine the impact of frame size smoothing on the video traffic to mitigate the effect of bit rate variabilities Compared to MPEG 4 Part 2 the H 264 AVC codec and SVC extension achieve lower average bit rates at the expense of significantly 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 streams in 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 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 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 primarily on encodings with fixed quantization scales is focused An additional motivation 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 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 The widespread adoption of the new H 264 AVC 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 characteristics and compression performance from a communication network perspective We study the Main profile of the H 264 AVC encoder using long Common Intermediate Format CIF 352x288 pixel resolution sequences Our study of the newest H 264 SVC extension analyzes 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 H 264 AVC and H 264 SVC single layer video traffic is significantly more variable than MPEG 4 Part 2 traffic under similar encoding conditions At the same time we confirm the significant average bit rate savings The increased bit rate variability is observed over a wide range of average qualities of the encoded streams and for all tested video sequences This makes the transport
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