Transcript Combat Inter-Symbol Interference with Equalization

Video Transcoding for Wireless Video
• Wireless Device Has Limited Resources
– Processing power
– Memory
– Display capability
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I
P
P
B
B
P
P
B
B
P
P
P
B
B
B
B
• Change GOP Structure
– Save memory
– Reduce decoding complexity
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P
P
P
P
P
P
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P
• Frame Size Down-sampling
– Large bit rate reduction
– Fit display screens of most
mobile devices
720 x 480
360 x 240
• MPEG1/2 to MPEG4
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Video Transcoding Techniques
• Previous Solution [Shanableh & Ghanbari, 00]
MV, MB_type, QP
MPEG2
Bitstream
MPEG1/2
Decoder
MPEG4
Encoder
MPEG4
Bitstream
Pixel Domain
• Proposed Solution
MV, MB_type, QP
MPEG2
Bitstream
MPEG1/2
Down-Decoder
MPEG4
Encoder
DCT-domain
MPEG4
Bitstream
2
Down-scale Decoder
MPEG2
bitstream
VLD
IQ
MVs
Down-scaled Video
DCT-domain
down sampling
DCT domain
IMC
VLD: variable length decoding
IQ:
inverse quantization
MC: motion compensation
FM:
frame memory
MV:
motion vector
FM
0
7
4x4
4x4
8x8
25
4x4
0
4x4
7
• Save More Than 50% of Memory
• Reduce Computational Complexity by 70%
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Experimental Results
• Average PSNR Degradation is 0.34dB at 384 kb/s
S. Liu, and A. C. Bovik, “A Fast and Memory Efficient Video Transcoder for Low Bit Rate Wireless
Communications ”, ICASSP 2002, accepted.
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26
PSNR (dB)
24
22
Pixel-domain transcoding method
The proposed DCT-domain transcoding method
20
6 Mb/s MPEG2
18
1 Mb/s MPEG4
16
0
50
100
Frame number
150
200
5
26
PSNR (dB)
24
22
Pixel-domain transcoding method
The proposed DCT-domain transcoding method
20
6 Mb/s MPEG2
18
768 Kb/s MPEG4
16
0
50
100
Frame number
150
200
6
26
Pixel domain method
PSNR (dB)
24
22
20
Proposed DCT domain method
18
6 Mb/s MPEG2
256 kb/s MPEG4
16
0
50
100
150
200
Frame number
7