| Abstract: |
Requantization is one of the tools for bit-rate reduction of
pre-encoded video to adapt it to various network bandwidth constraints.
Several recent works propose using Lagrangian optimization to find the
optimal quantization step for each coded macro-block, to meet a desired
rate at minimum distortion. We propose to extend the Lagrangian
optimization procedure by allowing the modification of quantized
coefficients index values, including setting their values to zero, in
addition to quantization step-size selection. Coefficient index value
modification and quantization step-size selection are optimally done
using a low-complexity trellis-based procedure in an MPEG-2 context.
The proposed requantization algorithm provides higher PSNR values than
the Lagrangian-based optimization method, which only handles the
selection of quantization steps, and still does not exceed considerably
its complexity. We also report on combining MSE and MAP requantization
methods, which are based on the estimated distribution of the DCT
coefficients, with the different optimization algorithms.
*Joint work with Michael Lavrentiev
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| Bio: |
David Malah Received the B.Sc. and M.Sc. degrees in 1964
and 1967, respectively,from the Technion - Israel Institute of
Technology, Haifa, Israel, and the PhD degree in 1971 from the
University of Minnesota, Minneapolis, Minnesota, all in Electrical
Engineering. During 1971-72 he was an Assistant Professor at the
Electrical Engineering Department of the University of New Brunswick,
Fredericton, NB, Canada. In 1972 he joined the Electrical Engineering
Department of the Technion, where he is a Professor, holding the
Elbit/Elron Chair in Electrical Engineering.
During the period 1979 to 1996 he spent about 5 years, cumulatively, of
sabbaticals and summer leaves at AT&T Bell Laboratories, Murray
Hill NJ, performing research in the areas of Speech and Image
Communication. During the summer of 1998 and the academic year
2000-2001 he was on a sabbatical leave at AT&T Labs, Florham Park
NJ, at the Speech Processing Research lab.
Since 1975 he has been the academic head of the Signal and Image
Processing Laboratory (SIPL), at the Technion, EE Dept., which is
active in Image and Speech Communication research and education. His
main research interests are in Image, Video, Speech and Audio Coding;
Speech Enhancement; Image Processing; Digital Watermarking, and in
Digital Signal Processing techniques.
He is a Fellow member of the IEEE since 1987.
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