Networked Interactive Media Codec Algorithm

Transcription

1 ICGST- CNIR, Volume (8), Issue (), July 008 Networked Interactive Media Codec Algorithm Kostas E. Psannis and Yutaka Ishibashi Department of Technology Management University of Macedonia, Thessaloniki 50 06, Greece Department of Computer Science and Engineering, Nagoya Institute of Technology, Nagoya , Japan Corresponding Author: Abstract This paper presents a novel networked interactive media codec algorithm. An MPEG/H.6 coded media sequence is typically partitioned into small intervals called GoP (Group of Pictures). An MPEG/H.6 video stream comprises intra-frames (I), predicted frames (P), and interpolated frames (B). This structure allows a simple realization of forward (normal)-pay operation but imposes several additional constraints on the other interactive functions. Implementation of the rewind operations requires that the decoder either decodes the whole GoP and store it, or it decodes the GoP up to the current frame to be displayed. Both of these techniques lead either to the requirement for large storage at the client machine (to store a fully decoded GoP) or massive decoding processing power (to fully decode a GoP at required displayed frame rate). Neither of these options is desirable. Furthermore, Fast Play (Fast Forward/Jump Forward) functions of MPEG/H.6 coded video present are problematic. When a P-/B- frame is requested, all the related previous P-/I-frames need to be sent over the network. This is likely to lead in considerable increase in communication bandwidth and decoding power compared to the normal-play mode. Several interactive algorithms are detailed with respect to additional resources. Finally an extensive comparative study has been carried out in order to determine the trade offs of the proposed media codec algorithm. Keywords Streaming Algorithms, Interactive Media Algorithms, VCR functionality.. Introduction Interactive access to video content is generally defined as a program or service controlled by the user and which can affect the content itself, the presentation manner of the content, or the presentation order of the content. Full range of interactive functions include play/resume, stop, pause, Jump Forward (JF)/ Jump Backward (JB), Fast Forward (FF)/ Fast Rewind FR), Slow down (SD), and Slow Reverse (SR), Rewind []-[]. The difficulty of supporting interactivity varies form one interactive function to another. A stop or pause followed by resume is relatively easy to support since there is no requirement for more bandwidth than is already allocated for normal playback. However, Fast Scanning {(FF), (FR), (JF), (JB)) functions involve displaying frames at multiple times the normal rate. Transporting and decoding frames at such high-rate is prohibitively expensive and is not feasible using the hardware decoders available today or in the foreseeable future [5]-[7]. Implementation of the full interactive functions with the MPEG/H.6 coded video presents a number of considerable challenges associated with video data storage and playout. An MPEG/H.6 video stream comprises intra-frames (I), predicted frames (P), and interpolated frames (B). According to MPEG/H.6 coding standards, I-frames are coded such that they are independent of any other frames in the sequence; P-frames are coded using motion estimation and each one has a dependency on the preceding I- or P- frame; finally the coding of B- frames depends on the two anchor frames - the preceding I/P frame and the following I/P frame [6]-[8]. In recent years several techniques for supporting interactivity for MPEG/H.6 code video streaming applications have been devised [9]-[]. In [9], [0] and {] interactive functions are supported by dropping parts of the original MPEG- video stream. Typically, this is performed once the video sequence is compressed and aims to reduce the transport and decoding requirements. These approaches introduce visual discontinuities during the interactive mode, due to the missing video information. Alternatively interactive functions can also be supported using separate copies of the video streams that are encoded at lower quality of the normal playback copy [], []. In these cases, there is no significant degradation in the visual quality. However, the number of pre-stored copies of the movie limits the speed-up granularity. Moreover, [] proposed a differently encoding pattern of the media traces. Full interactive functions are produced by encoding every N th frame of the original media traces as a sequence of I- P(Marionette) frames. This method achieves minimum additional resources at the server load/network

2 ICGST- CNIR, Volume (8), Issue (), July 008 bandwidth\decoder complexity and acceptable visual quality at the client s end. The remainder of the paper is organized as follows: In Section a review of the proposed interactive media streaming codec algorithms is detailed. In Section a novel interactive streaming media codec algorithm is presented accompany by simulations results. Moreover a comparative study has been carried out in order to determine the tradeoffs of the proposed interactive media algorithms with respect to network bandwidth visual quality. Section concludes the paper with final observations.. Review of Streaming Interactive Media Algorithms There are three different rates at which a video can flow from the disk of the server to the client display which should be taken into consideration while analyzing interactive functions. First, the video data has a retrieval rate going from the server s disk array to the main memory. Second, the data has a network transmission rate going from the server s memory to the client s memory. Lastly, the client decoder has a consumption rate at which it displays data from the client s memory. This section discusses and analyses the various proposed schemes for supporting interactive operations, according to the above requirements in the MPEG/H.6 -based media encoding. A. Drop parts of the original video stream [9]-[] Interactive operations can be supported by dropping parts of the original video stream. Dropping aims to reduce both the transport and decoding requirements of the interactive mode without causing significant degradation in the video quality. ) Send only I - P frames [9] This method sends only the I- and P-frames to support Fast Forward operations. Transmitting only the I- and P- frames of each GoPs a limited number of speedups can be achieved. The main problem with this method is that it increases the load on the network (the frame rate remains constant). For example consider a movie that is encoded into GoPs, where the GoPs Length is N=9 and the distance between the I-I/P frames is M=. The total number of I-P-B frames are in the GoPs are I=, P= 6 and B=8. The authors in [9] propose a storage pattern in order to minimize the disk overhead occurred by accessing k-sequences every second. Since the data being displayed is not contiguous, the authors recommend that the MPEG-based file is reordered. If the data were kept contiguous on the disks, then a disk rotation, seek and transfer must be performed for each frame, which increases the disk overhead in order to support faster.playback. The graph in figure shows that there is not a linear increase (%) in the network bandwidth during the Fast Forward (FF) mode as a function of N. For Fast Reverse playback operation the authors in [9] propose to send only the I-frames in reverse order. P-frames are based on forward prediction only and cannot be shown backwards. Increased Network Bandwidth 50,00% 5,00% 0,00% 5,00% Frame Rate =7fps,M= 0,00% 9 9 GoPs Length (N) Figure. The increased percentage of the network bandwidth as a Function of GoP Length (N). When the user requests a fast reverse mode the server must reschedule the disk to the desired frames in reverse order. The main problem is that the server, for a speedup of k, needs to read all I-frames from the k- GoPs. In addition, sending only the I-frames results in the enormous increase in the network bandwidth ) GoP-Skipping [0] The GoP-Skipping method proposed in [0] maintains the same playback frame rate and skip entire GoPs. (a) Normal playback GoPs GoPs GoPs n GoPs (b) Fast Forward mode (k times the normal rate) GoPs k GoPs n GoPs To achieve speedup k-times the normal play, every k- times GoPs is sent and consumed by the client s decoder. This method can achieve variable speedups. Figure shows the variable number of speedups as a function of skipped GoPs for N=5 and frame rate 0 fps. One limitation of this approach is that only independently decode-able GoPs can be used. If open GoPs are used, some extra processing must occur at the client-site increasing the requirements of the decoder complexity. Consider the display sequence of an open GoPs with GoPs length, N=6 and M=. (a) Display order I... B B P B6 I7 B8 B9 P0 BB I B P6 B7 B8 I9 (b) Transmission order I... P B B I7 B6 P0B8 B9 IBBP6BI9B7B8

3 ICGST- CNIR, Volume (8), Issue (), July 008 SpeedUps (sec) Skipped GoPs Figure. Number of speedups as a function of skipped GoPs For speedup k=, two GoPs are skipped. In this case frames and B would have to be discarded by the 6 client s decoder since the forward I-frame, that they depend on would be skipped. This phenomenon would result in slight hiccups at the client s set top box. It is worth mentioning that there are no increases in the resources at the server, network bandwidth and client s decoder when users switch to Fast Forward/ Fast Rewind. In the case of rewind, current MPEG-based hardware decoders cannot play frames of an MPEG-based GoPs in reverse order. Thus, the GoPs are sent in reverse order but the individual frames are played in forward order. The visual output will not look faster since the playback rate of each GoPs does not change. This however, may be acceptable to the end user who is searching backward for a particular part of a video. To demonstrate another drawback of this method, let a GoPs consist of 5 frames, the normal playback rate be 0fps and the speedup rate be four. Thus from the original stream, 5 frames are displayed, 0 are skipped, 5 are displayed, etc. This is a drawback because if the video has complex motion within the four seconds, then the information will be lost. Hence this method cannot be recommended because the visual quality will be degraded. ) Partial GoPs-skipping [] Another approach, proposed in [], is to partial skip GoPs rather than skip full GoPs. Consider the display sequence of an open GoPs with GoPs length, N=5 and M=. (a) Normal playback I P B B P7 B6 P0 B8 B9 P BB I6 B P9 B7 B8... (b) Fast playback I P B B I P 6 9 B7 B I The first four frames are considered as an independent sequence because they can be decoded independently. The first 7 or 0 or frames, can be considered as an independent sequence. For fast playback, independent sequences are retrieved and sent while the rest of the frames in each GoP are skipped. When using this method there are only a fixed number of speedup rates than can be achieved. Figure depicts the number of speedups as a function of transmitted frames. Speedups (sec) Trasmitted Frames Figure.Relative increase in the speedups as a function of the transmitted frames Like the skipping segment method, the same playback rate is maintained at the client. The bit rate required to be sent over the network will be increased, as well as the resources at the server. Consider a movie that is encoded into GoPs containing the following frames. (GoPs): I B B P B6 P7 B8 B9 P0 BB P B (GoPs): I6B7 B8 P9 B0 BP B B P5 B6B7 P8B9 B0 Each GoPs is 5 frames long (N=5). Like the skipping method, this method maintains the same playback rate at the client s end. Thus, instead of sending GoPs (0 frames/ sec) consisting of I- P - B frames during each cycle as in normal playback, the first frames are delivered. I B B P I B B P I B B P I B B P GoPs GoPs GoPs GoPs The average size of the first four frames or the fist seven frames of each GoP would be: I average + Paveage + ( Baveage) Average( I BB P ) Size = Iaverage + ( Paveage) + ( Baveage) Average (I BBPBBP)Size= 7 Figures shows the increase in the bit rate as a function of the supported speedups for GoPs Length N=5 and M= using typical characteristic of MPEG- compressed video In addition to the higher bandwidth over the network required over the Fast Forward mode, extra overhead may be incurred by the I/O subsystem. If a GoP is used as the retrieval block, normally the GoP is stored contiguously on disk. Assuming that during each I/O cycle GoP (5 frames) is retrieved, the disk executes one rotation, seek, and transfer. If four different frames from three GoPs ( frames) and three frames from the next GoPs are retrieved during each cycle, the disk must perform four rotations, seeks, and retrievals for every 5 frames retrieved

4 ICGST- CNIR, Volume (8), Issue (), July 008 SpeedUps (sec),5,5,5 0, Increase bit rate (%) Figure. Relative increase in the bit rate as a function of the supported speedups This procedure increases the overhead in processing the fast mode request. It is worth mentioning that using IBBP structure rewind functions can no be implemented due to the P-, and B- frames dependencies. B. Separate Copies of the movie [],[] Instead of dropping frames after compression, some researchers suggested supporting interactive operations using separately copies of the movie that are encoded at lower quality than the quality of the normal playback. ) Skipping row of frames [] This approach is based on encoding separate copies of the movie to be used for interactive operations in a Video On Demand (VOD) system. Each copy is generated by skipping rows of frames before compression. The server maintains multiple different encoded versions of each movie. The normal version is used for normal-speed playback. The other versions, which are referred to as the scan version, are used for Fast Scanning (FS) operations. Each scan version is used to support both Fast Forward Scanning (FFS) and Backward Fast Scanning (BFS). For a given speedup factor, the corresponding scan version is obtained by encoding a subset of the row uncompressed frames of the original movie at a sampling rate of -to-s, where s is the skip factor. The skip factor defines the sampling rate. Scan versions are encoded in a way such that, when played back at the normal frame rate, they give a perception of a faster video in the forward or backward direction. The server switches between various versions depending on the requested interactive operations (only one version is transmitted at a given instant time). It is worth mentioning that the interactive scanning operations] can be supported with some extra network bandwidth. Encoding a sample of the row frames may result in higher values of P average ( s), Baverage ( s). The encoder can control the size of P-B frames in the scan mode using two predefined thresholds. T ( P) = Pmax( + SP) () T ( B) = Bmax( + SB) where Pmax and Bmax are for normal version and S P, S B are nonnegative constants. A P (B) frame is encoded such that its size is no higher than T( P){ T( B)}. On the other hand this results in variable video quality during Fast Scanning operations. Generating separate copies for Fast Scanning operations comes at the expense of extra storage of the server and some variability in the quality of the motion picture during the Fast Scanning (FS) periods. Figure 5 depicts the percentage of the increase in the storage overhead as a function of N using typical characteristics of MPEG- compressed video with skip factor s = and S P = S B = 0. For n scan versions (variable speedups) the relative increase in the storage requirement is given by i W scan ( s) W Storage Increase (%) normal GoPs Length (N) Figure 5. Relative increase of the storage overhead as a function of GoPs Length (N) ) Alternative special file [] In this method a special file is created specifically for use in Fast Forward/ Fast Rewind mode and multi-resolution viewing. The encoding of the special file can be done in two ways. If the original uncompressed file is available, then every n-th frame is encoded for a speedup of n. If the original file does not exist, the compressed stream is first uncompressed and every nth frame is then recompressed. The alternative file can be created based on the motion within the original file. During periods of little motion, large numbers of frames are skipped from the original file. During periods of high motion, lower numbers of frames are skipped. The special file is created to be approximately 0-5% of the original file so that the average bit rate of the resulting file is less than or equal to the average bit rate of the original. This guarantees that, when switching form normal playback to fast playback, there is no increase in the load on the server or the network. The special file is encoded at both lower temporal resolution and spatial resolution than the original file. For example consider a video, which was encoded at 0 frames per second with an average bit rate of.5 Mbps. Let special file be a separately encoded lower resolution

5 ICGST- CNIR, Volume (8), Issue (), July 008 file, encoded at 0 frames per second with frame format ( I B B B B I ) and an average bit rate of only 0.5Mbps. To support multi-resolution the special file is shown at 0 frames per second with an average bit rate of 0.5Mbps. An additional mechanism is needed to allow the client to change the decoder s consumption rate. To support Fast Forward (FF), the special file is shown at the same speed as its original file, or.5mbps, which is 0 frames per second, a speedup of three. This is conformed to the goal of requiring no much additional bit rate for the Fast Forward/Rewind than that is already allocated for the original file. In addition, when creating the special file the authors in [] propose to update the bit-stream so that it can support both the Fast Forward (FF) and Fast Rewind (FR) mode. To solve the problems of dependencies in MPEG- frames the authors propose two strategies. First, macroblocks are forced to be either intra-coded (I) or purely interpolated (B). P macroblocks are not acceptable because they have a unidirectional dependency, which would make it impossible to play frames back in reverse directions. This however, would not entirely solve the problem since the interpolated B macroblocks have different distance vectors with respect to the two reference frames. Hence if the reference frames are presented in the reverse order (as in the case of rewind), the decoding would be incorrect. To overcome this problem, the distance vector are forced to be equal in both directions, and set equal to the smaller of the two vectors. This makes the interpolated frames symmetrical with respect to both the forward and backward reference frames and enables them to be decoded correctly even if the reference frames are presented in reverse order. Figure 6 depicts the increase in the storage at the server as a function of GoPs (N), using typical characteristics of MPEG- compressed video (Appendix B.) with the frame format of the special file I B B B B I and encoding every third frame of the original file. Increase Storage (%) GoPs Length (N) Figure 6. Relative increase of the storage as a function of N The main advantages of using this method are that it does not increase the load on the server since it can be created with the same playback rate as the original file. Also the file can be created, as described above, such that it can be shown forward and backward and in multi-resolution viewing. The main disadvantage of using this scheme is that a separate file must be created for each speedup rate, increasing the amount of storage used in the system and hence an increase in cost.. Proposed Interactive Media Streaming Algorithm In this efficient approach the server maintains multiple differently encoded versions of each video streams in order to support interactive functionality. One version, which is referred to as the normal version is used for normal-speed playback. The other versions are referred to as interactive versions. Each interactive version is used to support Fast/Jump Forward/Backward Slow Down/Reverse and Reverse at a variable speedup. The server switches between the various versions depending on the requested interactive function. Assume that I- frame is always the start point of interactive mode. Since I- frames are decoded independently, switching from normal play to interactive mode and vice versa can been done very efficiently. Note that only one version is transmitted at a given instant time. The proposed interactive streams can be employed to any frame-based codec algorithm (MPEG-/ and MPEG-/H.6) [7]. The corresponding interactive version is obtained by encoding every (k-)-th (i.e., uncompressed) frame of the original movie as a sequence of I- P(Marionette)-Pi(k) frames. Effectively this results P(Marionette) in repeating the previous I-frame in the decoder, enhancing the visual quality during the interactive mode. The encoding pattern is obtained by encoding the original uncompressed video data as follows Io P(M)P(k)... i PN- (k)pn ( k ) () subject to i N k N, N denotes the GoP length and k denotes the Reference Frame Selection (RFS). P i ( k )- frames are coded using motion estimation and each one has a dependency only to th the preceding k - frame. A P i ( k )-frame is not a full frame. Instead, it is a Predictive video frame. This means that a P i ( k ) frame only stores the data that has changed th from the preceding k -frame. For instance, for reference frame selection (RFS) k= (short term motion compensation reference), has a dependency to the P I0 P I0 P P P P P P preceding, has a dependency to the preceding, has a dependency to the preceding, has a dependency to the preceding, and for the final frame in a GOP, has a dependency to the preceding. Similarly for reference frame selection (RFS) k= (long term motion compensation reference), each of P, P, P and P frames have a dependency to the preceding I0. P5 has a dependency to the preceding P, P6 has a dependency to the preceding P and for the 5

6 ICGST- CNIR, Volume (8), Issue (), July 008 final frame in a GOP, preceding P 0 P has a dependency to the.note that for k= motion compensation reference frame implies the conventional H.6/AVC I-P structure. The full interactive functions can be supported as follows. Fast Forward /Rewind (FF/FR) and Jump Forward/Backward (JF/JB) functions can be supported by abstracting all the I-type frames of the original (uncompressed) movie in the forward/backward direction and encoding each frame as a sequence of I-P(M)Pi(K) frames. Moreover, Rewind operations can be supported by abstracting all the I-type frames of the original (uncompressed) movie in reverse order and generate P(M Pi(K)) frames as many as P- and B in a GoPs of normal playback. Slow Down/Reverse functions can be supported by abstracting all the I-type frames of the original uncompressed movie in the forward/backward order and generate P(M)Pi(k) frames as many as P- and B-frames in a recording ratio (RR) of normal playback.. Performance Evaluation Commonly used measures for the distortion between an original picture (before encoding) of horizontal size w and the vertical size b and its reconstructed counterpart (after decoding) is the Peak Signal-to-Noise-Ratio (PSNR). The following formula can be used to assess the visual quality of a sequence. 55 PSNR = 0 log( )( db) where i= j= x rec MSE h w MSE = {( x h w x org ( i, j) ( i, j) org ( i, j) x rec ( i, j)} where and denote the single pixel magnitudes of the original and the reconstructed picture and h w is the picture size. Most studies use PSNR as the main quantitative metric for measuring the video quality. There are two types of criteria that can be used for the evaluation of video quality; subjective and objective. It is difficult to do subjective rating because it is not mathematically repeatable. For this reason we measure the visual quality of the interactive mode using the Peak Signal-to-Noise Ratio (PSNR). We use the PSNR of the Y-component of a decoded frame. The PSNR is obtained by comparing the original row frame with its decoded version with encoding being done using the proposed media algorithms. We simulate the scenario of the H.6-based video transmission. Simulations were done using the H.6 Test Model (H.6/AVC Software Coordination, software version: JM.0) [ ]. All test sequences are in QCIF format (76 x pixels/frame) and encoded at target frame rate 5 frames/s, the number of frames to be encoded/decoded is 50 frames. The computers used for the experiments is Pentium (R) CPU,,6Gz, GB of RAM, available storage space GB and a network channel at 00kbps. The first frame in a GoP is Intra (I-) frame and the remaining consecutive frames are P(M) and Pi(k) coded. The simulations were carried out on the following QCIF video traces: foreman and Coastguard at 00 Kbps channel throughput and for the I-P(M)-Pi(k) the Reference Frame Selection (RFS), k=. Y PSNR (db) Frame Index Coastguard foreman Figure 7. PSNR as a function of frame index for different types of video sequences Figure 7 depicts the PSNR for the encoded frames using the proposed encoding algorithm for different types of video sequences. The average PSNR value for the 50- frames is 8., db for Foreman the video trace and 8. db for the Coastguard video trace The average quality is slightly better under the Foreman (little motion) video sequence due to I-P(M)-Pi(K) frames structure. Figure 8 and Figure 9 depict the PSNR for all the interactive media codec algorithms for the Foreman and the Coastguard video traces respectively. From Figure 8 we can see that the proposed algorithm achieves greater PSNR (db) compared to all the other algorithms. Specifically it achieves an advantage of.5 db compared to Send only I-P frames approach. Y PSNR (db) Foreman Video Frame Index Send only I - P frames Proposed Algorithm GoP-skipping Partial GoPs-Skipping Skipping row of frames Alternative Special File Figure 8. PSNR as a function of frame index for all the interactive media algorithms for the foreman video trace. 6

7 ICGST- CNIR, Volume (8), Issue (), July 008 Coastguard Video Y PSNR (db) Frame Index Send only I - P frames Proposed Algorithm GoP-skipping Partial GoPs-Skipping Skipping row of frames Alternative Special File Figure 9. PSNR as a function of frame index for all the interactive media algorithms for the coastguard video trace. Similarly from Figure 9 we can see that the proposed algorithm achieves superior PSNR (db) compared to all the other algorithms. Specifically it achieves an advantage of. db compared to Alternative Special File approach. In order to validate the proposed interactive media codec algorithm a subjective comparative study has been also carried out. Figure 0 depicts some typical snapshots for the proposed interactive media codec algorithm, the Send only I-P frames approach and the Special Alternative File method. a b c Coastguard video Size (bytes) Figure 0. Size (bytes) Frame-Size I-P(M)-Pi(k) Frame Number Frame Size of the proposed interactive media codec algorithm for the Coastguard video trace Foreman video Frame-Size I-P(M)-Pi(k) a b Figure 0. Snapshots of Coastguard () and Foreman () video traces for the Alternative Special File method (,)a, Send only I- P frames approach (,)b and the proposed interactive media codec algorithm (,)c. It can be seen that for both video traces, coastguard and foreman, the proposed interactive media codec algorithm outperforms the other schemes, Send only I-P frames approach and the Alternative Special File method, since it achieves better visual quality.the average frame size of the proposed interactive media codec algorithm is illustrated in Fig. and Fig. for the Coastguard and the Foreman video traces respectively. From the same Figures it can be seen that the P(M) and Pi(K) frames have less bits that the I-frames due to I-P(M)-Pi(k) frames structure. c Frame Number Figure. Frame Size of the proposed interactive media codec algorithm for the foreman video trace.. Conclusion An MPEG/H.6 coded media sequence is typically partitioned into small intervals called GoP (Group of Pictures). This structure allows a simple realization of forward (normal)-pay operation but imposes several additional constraints on the other interactive functions (Fast/Jump Forward, Fast/Jump Rewind, Slow Reverse/ Forward, and Reverse). In this paper, we investigated the constraints of supporting interactive media streaming with respect to additional resources and Visual Quality of the proposed algorithms. By proper encoding MPEG/ H.6 media streams, I-P(M)-Pi(k) frames, of the original video sequence, interactive functionality can be supported with considerably reduced network bandwidth and decoder complexity and acceptable visual quality at the clients end. A comparative study has been also carried out in order to determine the tradeoffs between the different methods. Future work involves network simulation of all the algorithms over combined networks from wireline to wireless links. 7

8 ICGST- CNIR, Volume (8), Issue (), July References [] Kostas. E. Psannis, M. G. Hadjinicolaou, and A. Krikelis, MPEG- streaming of full interactive content, IEEE Transactions on Circuits and Systems for Video Technology, vol. 6, no., pp , 006. [] Kostas Psannis, MPEG-based Video over High Speed Downlink Packet Access Wireless Networks, ICGST International Journal on Computer Networks and Internet Research, Vol. (5), Issue (), pages 5-5, 006 [] A. Jalal and S. Kim, Advanced Performance Achievement using Multi- Algorithmic Approach of Video Transcoder for Low Bit rate Wireless Communication, ICGST International Journal on Graphics, Vision and Image Processing}, Vol. (5), Issue (9), 005 [] Yang, K., Huang, C., and Wang, J Design of frame dependency for VCR streaming videos. Image Commun. Pp (Jun. 007). [5] Pengpeng Ni, Damir Isovic, Gerhard Fohler, Userfriendly H.6/AVC for remote browsing Proc.of the th annual ACM international conference on Multimedia, pp -7, October 006. [6] Karczewicz, M.; Kurceren, R., The SP- and SIframes design for H.6/AVC, IEEE Transactions on Circuits and Systems for Video Technology, Volume, Issue 7, pp 67 6, July 00. [7] Advanced Video Coding for Generic Audiovisual Services, ITU-T Rec. H.6 and ISO/IEC 96-0 (MPEG- AVC), ITU-T and ISO/IEC JTC, Version : May 00, Version : May 00, Version : Mar. 005, Version : Sept. 005, Version 5 and Version 6: June 006, Version 7: Apr. 007, Version 8 (including SVC extension): Consented in July 007. [8] Kostas. Psannis, Yutaka Ishibashi and Marios Hadjinicolaou, A Novel Method for supporting Full Interactive Media Stream over IP Network, ICGST International Journal on Graphics, Vision and Image Processing, Vol.(), pp 5-, 005. [9] D. Venkatesh, A Scalable Video-on Demand Service for the Provision of VCR-Like Functions, Proc IEEE Multimedia, pp. 65-7, 995. [0] M-S. Chen, D.D. Kandlur, and P.S. Yin, Support for fully interactive playout in a disk-array-based video server. In Proc of Second International Conference on Multimedia, pp 9-98, Oct 99. []Banu Ozden, Alexandros Biliris, Rajeen Rastogi, Avi Silberschatz. A Low-Cost storage Server for Movie on Demand Databases. In: Proc. of the 0th VLD Conference, Santiago,.pp , 99. []Marwan Krunz, George Apostolopoulos., Efficient Support for interactive scanning operations in MPEGbased video on video on demand, Multimedia Systems, vol.8, no., Jan. 000, pp.0-6 []Michael Vernick, Chitra Venkatramani, Tzi-Cher Chinueh, Adventure in Building the Stony Brook Video Server. In Proc ACM Multimedia, Boston, Nov 996, pp [] H.6/AVC Software Coordination, software version: JM.0 ( Kostas Psannis was born in Thessaloniki, Greece. He was awarded, in 006, a research grant by International Information Science Foundation sponsored by Ministry of Education, Science, and Technology, Japan. Since 00 he has been a Visiting Assistant Professor in the Department of Technology Management, University of Macedonia, Greece. Since 005 he has been a Visiting Assistant Professor in the Department of Computer Engineering and Telecommunications, University of Western Macedonia, Greece. From 00 to 00, he was a Visiting Postdoctoral Research Fellow in the Department of Computer Science and Engineering, Graduate School of Engineering, Nagoya Institute of Technology, Japan. He has extensive research, development, and consulting experience in the area of telecommunications technologies. Since 999, he has participated in several R&D funded projects as a Research Assistant in the Department of Electronic and Computer Engineering, School of Engineering and Design, Brunel University, UK. From 00 to 00, he was awarded the British Chevening scholarship sponsored by the British Government. He has more than 0 publications in conferences and peer-reviewed journals. He received a degree in physics from Aristotle University of Thessaloniki, Greece, and the Ph.D. degree from the Department of Electronic and Computer Engineering of Brunel University, UK. He is a Member of the IEEE, ACM and IET. Yutaka Ishibashi received the B.S., M.S., and Ph.D. degrees from Nagoya Institute of Technology, Nagoya, Japan, in 98, 98, and 990, respectively. From 98 to 99, he was with NTT Laboratories. In 99, as an Associate Professor, he joined Nagoya Institute of Technology, in which he is now a Professor in the Department of Computer Science and Engineering, Graduate School of Engineering. From June 000 to March 00, he was a Visiting Professor in the Department of Computer Science and Engineering at the University of South Florida. His research interests include networked multimedia applications, media synchronization algorithms, and QoS control. He is a Member of the IEEE, ACM, Information Processing Society of Japan, the Institute of Image Information and Television Engineers, and the Virtual Reality Society of Japan. 8