United States Patent 7,471,840
Toebes , et al. December 30, 2008

Two-dimensional variable length coding of runs of zero and non-zero transform coefficients for image compression 


A method, apparatus, and carrier medium to encode a series of quantized transform coefficients. The method includes identifying events that each includes a run of zero-valued coefficients preceding a run of one or more non-zero-valued coefficients, and for each such event, jointly encoding the run lengths of the preceding run of zero-valued coefficients and the following run of non-zero-valued coefficients with a codeword, such that for at least some events, relatively more likely-to-occur pairs of runlengths are encoded by a shorter codeword than relatively less likely-to-occur runlengths. The method further includes encoding each amplitude in the run of consecutive non-zero-valued coefficients, and encoding the signs of such coefficients. The method is applicable to encoding a region in the series where there is likely to be a cluster of non-zero-valued coefficients.

Inventors: Toebes; John A. (Cary, NC), Chen; Wen-hsiung (Sunnyvale, CA), Wu; Fang (Pleasanton, CA), Rosenfeld; Dov (Oakland, CA),
Assignee: Cisco Technology, Inc. (San Jose, CA)
Appl. No.: 10/922,508
Filed: August 18, 2004

Full patent text at USPTO