"Rate Shaping by Block Dropping for Transmission of MPEG-precoded Video over Channels of Dynamic Bandwidth"

presented at ACM Multimedia '96, Boston, Nov. 1996.

ABSTRACT

In the transmission of a precoded, stored video such as that in video-on-demand systems , it is often necessary to reduce the bit rate of the compressed video in cases that the network capacity is reduced. This paper proposes a novel block-dropping approach for rate shaping of MPEG-precompressed video. A directional spatial interpolation scheme is incorporated at the receiver to reconstruct faithfully a large percentage of the blocks that are intelligently dropped to meet the constraint of reduced bandwidth. The blocks are dropped in a way that is optimal in the rate-distortion sense. The new approach is conceptually quite different from conventional approaches in which coefficients (usually high frequency coefficients) are eliminated. Experimental results show that the proposed scheme can provide significantly higher peak signal-to-noise ratio (PSNR) and much better visual quality than conventional approaches. We also show that by jointly dropping blocks and coefficients, the bit rate can be reduced further, and additional gain is obtained.

Keywords

rate shaping, quality of service, video on demand, directional interpolation, block dropping, wireless transmission, video compression.

Proposed system diagram

The last function unit is a key component in the proposed system. Note conventional approaches do not have this function unit. For details about the interpolation scheme used in our system, please click here.
Similar idea has been used in low bit rate video coding.

Sample result

"Claire" sequence, precoded at 341 Kbps, and rate-shaped at 298 Kbps
Block-drop. approach Coef.-truncation (traditional) approach

Paper

· Postscript version of the paper (567 K)

Last update: Oct. 2, 1996.

wzeng@ee.princeton.edu