By Sreya Chakraborty Under guidance of Dr. K.R.Rao April 28,2011 Smooth streaming is a challenge in areas where bandwidth is low or limited. 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. Implications of video traffic smoothing on the numbers of statistically multiplexed H.264SVC, H.264/AVC and MPEG-4 part 2 streams [2] Traditional digital video transmission and storage systems are based on H.222.0, H.320 [7] International video coding standards H.262, H.263 and MPEG-4 [1],[2] Simulcast provides similar functionalities as a scalable bit stream. Effectiveness of two elementary techniques for mitigating high traffic variability Buffered multiplexing: Identify the multiplexer buffer sizes required to support maximum number of streams. Video traffic smoothingFrom the wide spectrum of video traffic smoothing techniques two approaches are: Optimal Smoothing minimizes the traffic variability. Computational complexity of O(M), M is the number of video frames. Basic Smoothing averages the sizes of a prescribed number of video frames. Computationally simple O(1)Fig.1 Basic compression system [10]Fig.2 Typical coding system [10]Fig. 3: Block diagram of H.264 [14]Fig.4:Luma prediction (intra-prediction) modes in H.264 [15](a) (b) :Fig.5: Macroblock portioning in H.264 for inter prediction (a) (L-R) 16x16, 8x16, 16x8, 8x8 blocks; (b) (L-R) 8x8, 4x8, 8x4, 4x4 blocks [15] JM Software [12]: This software is a product of Joint Video Team (JVT) of ISO/IEC MPEG and ITU-T VCEG. The latest version of JM Software is 17.2. It supports both planar and interleaved/packed raw image data (viz., yuv, rgb). The input file is a configuration file (text file) and some of the parameters passed in that file are: Input file Number of frames to be encoded Frame rate Output frame width and Height Profile, level selection GOP size Bit rate control JSVM software [13]: This software is a product of Joint Video Team (JVT) of ISO/IEC MPEG and ITU-T VCEG. The input file is a configuration file (text file) and some of the parameters passed in that file are: Input file Number of frames to be encoded Frame rate Output frame width and Height Profile, level selection GOP size Bit rate control JM(17.2) Performance Analysis JM Performance in Baseline Profile Video Sequence - akiyo_qcif Number of frames encoded –25 GOP - IBPBPBPBPB Quantization parameter–25, 30, 35, 40 Number of reference frames -3 Video Sequences Used: Baseline File Size: 3713 KB QCIF format –176 x 144 YUV –4:2:0Fig.6:PSNR vs QP for Baseline profile of akiyo_qcifFig. 7: Encoding time vs QP for baseline profile of akiyo_qcif Scalable Video Coding (SVC) will be an extension of the H.264 / MPEG-4 Advanced Video Coding (AVC) standard ‰ Starting point of SVC extension was designed and proposed by Fraunhofer Institute HHI ‰ Standardization of SVC extension is still under way To serve different needs of different users with different displays connected through different network links by using a single bit stream, i.e., a single coded version of the video content: ‰ Spatial scalability: Choose appropriate resolution ‰ Temporal scalability: Choose convenient frame rate ‰ Quality scalability: Choose suitable data rate by removing parts of the bit streamFig. 8: B frame prediction structures [8]• Hierarchical B frame is used. • For the H.264 SVC encodings GoP structure IBBBBBBBBBBBBBBB (16 frames, 15 B frames per I frame) denoted by G 16-B15 • Statistical video traffic analysis demonstrates that these encoding parameters settings and GoP structures result overall in a very good rate distortion efficiencies for the respective encoders. The SVC extension is built on H.264 / MPEG-4 AVC and re-uses most of its innovative components. As a distinctive feature, SVC generates an H.264 / MPEG-4 AVC compliant, i.e., backwards-compatible base layer and one or several enhancement layer(s). The base layer bit stream corresponds to a minimum quality, frame rate, and resolution (e.g., QCIF video), and the enhancement layer bit streams represent the same video at gradually increased quality and/or increased resolution (e.g., CIF) and/or increased frame rate.Fig.9: Block diagram of SVC [1]Fig.10: SNR Scalable coder Upper layer Base layerFig.11: Decoding process for SNR scalability ‰ Ease of adaptation to different terminal capabilities ‰ Resource conserving transmission, storage, and display of video, e.g., in surveillance applications ‰ Higher transmission robustness, if combined with unequal error protection ‰ Ease of Multicast Streaming through heterogeneous networks Incorporates multiple streams in a single stream. Customized Can send a single video stream to multiple heterogenous clients Bandwidth and storage space is saved. The base video stream layer of lower quality can be stored separately, instead of storing all the layers. This might be useful for video surveillance H.264 SVC can give a decent (manageable) picture quality even at 20-40% packet loss in the network while the maximum tolerable packet loss for H.264 AVC might be around 1-5%.• H.264 SVC [1] video encoding is expected to be widely adopted for wired and wireless networks video transport due to their compression efficiency. • SVC enables the transmission and decoding of partial bit streams to provide video services with lower temporal or spatial resolutions. JSVM Performance Analysis [11] JSVM Performance in Baseline Profile Video Sequence –Die Hard Number of frames encoded –30 GOP – G16B15 Quantization parameter–25, 30, 35, 40Fig.12: Video sequence Die Hard [11]Trace preview for the video sequence Die Hard [11]Fig. 13: Peak/Mean of size vs Average quality (PSNR-Y) for Die Hard [11]Fig. 14: Average quality (PSNR-Y) vs Average bit rate for Die Hard [11]Fig.15: Video sequence Citizen Kane [11]Fig.16: Peak/Mean of size vs Average quality
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