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Proceedings Paper

Runlength encoding of quantized discrete cosine transform (DCT) coefficients
Author(s): Viresh Ratnakar; Ephraim Feig; Eric Viscito; Sudhakar Kalluri
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Paper Abstract

Runlength encoding is used in image and video compression methods to efficiently store quantized Discrete Cosine Transform coefficients. The coefficients for each block are scanned in a zig-zag fashion, and runs of zeros are entropy coded. In this paper we present a comparison of the bit-rate resulting from runlength encoding with the bit-rate calculated as the coefficient-wise sum of entropies. Our experiments with several images show that the two are very close in practice. This is a useful result, for example, for designing quantization matrices to meet any bit-rate requirement. We also present an analytical framework to study these bit- rates. We consider two variants of runlength encoding. In the first one, the symbols that are entropy-coded are (runlength, value) pairs. In the second variant, which is the one used in JPEG, values are grouped together into categories based on magnitude.

Paper Details

Date Published: 17 April 1995
PDF: 9 pages
Proc. SPIE 2419, Digital Video Compression: Algorithms and Technologies 1995, (17 April 1995); doi: 10.1117/12.206376
Show Author Affiliations
Viresh Ratnakar, Univ. of Wisconsin/Madison (United States)
Ephraim Feig, IBM Thomas J. Watson Research Ctr. (United States)
Eric Viscito, IBM Thomas J. Watson Research Ctr. (United States)
Sudhakar Kalluri, Univ. of Delaware (United States)

Published in SPIE Proceedings Vol. 2419:
Digital Video Compression: Algorithms and Technologies 1995
Arturo A. Rodriguez; Robert J. Safranek; Edward J. Delp, Editor(s)

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