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MPEG Video Streaming with VCR Functionality

MPEG Video Streaming with VCR Functionality. Chia-Wen Lin, Jian Zhou, Jeongnam Youn, Ming-Ting Sun IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY, MARCH 2001. Introduction.

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MPEG Video Streaming with VCR Functionality

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  1. MPEG Video Streaming with VCR Functionality Chia-Wen Lin, Jian Zhou, Jeongnam Youn, Ming-Ting Sun IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY, MARCH 2001

  2. Introduction • A key technique that enables fast and user friendly browsing of multimedia content is to provide VCR functionality. • VCR functionality includes forward, backward, random access, fast-forward/backward. • MPEG video compression is based on motion compensated predictive coding with an I-B-P frame structure. • We investigate the impacts of the VCR functionality on the network traffic and the video decoder complexity.

  3. Introduction(cont.) • We propose using reverse-encoded bitstreams at the server to resolve the problem of reverse play. • We propose a frame-selection scheme at the server to minimize the required network bandwidth and the decoder complexity. • We describe our implementation of an MPEG-4 video streaming system supporting the VCR functionality.

  4. Impacts of VCR Functionality on Decoder Complexity and Network Traffics • Random Access • Fast-Forward Play speed-up factor K = 6

  5. Fast-Forward Play We assume the start point of a fast-forward operation is an I-frame, L= gcd( k, N ) After k/L GOPs, the frame to be displayed will again be an I-frame.

  6. If N is relatively large compared to k, will grow almost linearly as k increases, thereby leading to a linear increase of the decoding complexity and the network traffics

  7. Average number frames and bit-rates for sending the “Moblie and Calendar” sequence over network with respect to different speed-up factors in fast-forward play

  8. Supporting Full VCR Functionality with Minimal Network Bandwidth and Decoder Effort • To solve the problem of the backward-play operation, we propose to add a reverse-encoded bitstream in the server. • After we finish the encoding and reach the last frame of the video sequence, we encode the video frames in the reverse order to generate a reverse-encoded bitstream.

  9. We arrange the encoding so that the I-frame in the reverse bitstream are interleaved between I-frames in the forward stream. • Two metadata files recording the location of the frames in each compressed bitstream are also generated so that the server can switch from the forward-encoded bitstream to the reverse-encoded bitstream.

  10. Dual Bitstreams with Least-Cost Frame Selection • CR_C : the cost of decoding the next requested P-frame from the current displayed frame. • CR_FI : the cost of decoding the next requested P-frame from the closest I-frame in the forward bitstream. • CR_RI : the cost of decoding the next requested P-frame from the closest I-frame in the reverse-encoded bitstream. • The reference frame to the next requested frame with the least cost will be chosen to initiate the decoding.

  11. Example : Fast-backward Speed-up factor=6,the current position is frame 20, which was decoded using the reverse bitstream(R)display sequence : 20,14,8,2 only need to send and decode 6 frames Without least-cost scheme, we need to send and decode 13 frames from the reverse bitstream.

  12. Example : Random access The client requests random access to frame 22 when the current decoded frame if frame 3 Only need to send and decode 2 frames Without least-cost scheme, we require 9 frame from frame 14 using the forward bitstream.

  13. Performance Analysis of the Proposed Dual-Bitstream Least-Cost Method • Random Access Frame Nj is the random access point NRI is the position of the I-frame in the reverse bitstream We assume N is even and NRI is odd

  14. Fast-forward Play

  15. When N and k are coprime(L=1) In fact for the cases that N and k are not coprime, the result of (7) and (8) are still very close.

  16. Average number of frames to be sent for decoding a frame and average bit-rates to send “Moblie and Calendar” sequence using the proposed method with respect to different speed-up factors

  17. Drift Compensation

  18. DFR /DRF: a bitstream used for switching from the I- or P-frames of the forward/reverse bitstream to the P-frames of the reverse/forward bitstream • Pred(A, B) represents an inter-frame prediction process that frame B is predicted from the reference frame A. • DFRn = Pred( Fn , Rn –1 ) • DRFn = Pred( Rn , Fn +1 )

  19. Implementation of an MPEG-4 Video Streaming System with Full VCR Functionality

  20. Conclusion • Reverse-encoded bitstream to simplify the client machine complexity. • Minimum-cost frame-selection scheme to minimize the number of frames needed to be sent over the network and to be decoded. • Drift-compensation scheme to limit the drift. • An MPEG-4 video streaming system with full VCR functionality can be implemented to minimize the required network bandwidth and decoder complexity.

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