Efficient Reverse-Play Algorithms for MPEG Video With VCR Support
Chang-Hong Fu, Yui-Lam Chan, and Wang-Chi Siu
CSVT 2006
Outline
Introduction MB-Based Reversed-Play Video
Streaming System Simulation Results Ideas of Backward Macroblocks
Introduction (1)
Environments
Stored videos
Limited storage:1. Displayed buffer2. Reference buffer
server
clients
Introduction (2)
Transmission of stored videos Download mode
Downloading the entire video before playback
Unacceptable delay time Streaming mode
Playing the video while downloading it Hardly supporting VCR functionality due
to the frame structure in MPEG standardsI P P P…
Introduction (3)
0..n-1
n-1
0..n-2
I …
0 1 2 n LL-1
P P P P I…
Current frame
Introduction (4) Bandwidth requirement for forward
play/reverse play
Total sent frames for playing a GOP reversely: (Average: )
L = 151.5 Mb/s30fps
151413
MB-Based Reversed-Play Video Streaming System (1) MB-based reversed-play algorithm
MBs are categorized into several classes
Transmission of some MBs can be avoided Some redundant MBs need not be decoded Increasing the complexity of the server to
reduce the client load and network load
n-2 n-1 n
Next to be displayed
1
2 3
3mv
mv
MB-Based Reversed-Play Video Streaming System (2) BMB (Backward-MB) and FMB
(Forward-MB) BMB: mvn
(k,j) = (0, 0) MBn-1(k,j) is a BMB
Percentage of BMBs
MBn(k,j) = MBn-1
(k,j) + en(k,j)
MBn-1(k,j) = MBn
(k,j) - en(k,j)
The server transmits VLC{Q[DCT(-en
(k,j))]} to the decoder
nth frame kth row and jth column
MB-Based Reversed-Play Video Streaming System (3)
Encoding of -en(k,j) at the server
DCT(-en(k,j)) = -DCT(en
(k,j)) Q[DCT(-en
(k,j))] = -Q[DCT(en(k,j))]
VLC{Q[DCT(-en(k,j))]} = ?
Sign FLC
10 2’s complement
MB-Based Reversed-Play Video Streaming System (4)
Non-MC FMB mvn-1
(k,l) = 0 MBn-1(k,l) is a non-MC FMB
MBn-1(k,l) = MC(mvn-2
(k,l)) + en-2(k,l) + en-1
(k,l)
Q[DCT(en-2
(k,l) + en-1(k,l))] = Q[DCT(en-2
(k,l))] + Q[DCT(en-1(k,l))]
The server transmits VLC{Q[DCT(en-2(k,l) + en-1
(k,l))]} to the decodere1 e2 e3 e4
MB-Based Reversed-Play Video Streaming System (5)
Simulation results (1)
MPEG-2 coder GOP size = 15 with only I-frames
and P-frames 30 fps with 200 frames CIF or SIF (Salesman, Table tennis,
and Football) and QCIF (Claire, Grandma, and Carphone) format
Simulation Results (2)
BMB
Non-MC FMB
(Sign Inversion)(DCT Addition)
Simulation Results (3)
Simulation Results (4)Salesman 1.5Mb/s
Carphone 128kb/s
nn-1n-2n-3n-4n-5
BMB
Simulation Results (5)
Ideas of BMBs
Error concealment of BMBs Encoding residual of BMBs