Title :
Post processing transform coded images using edges
Author :
Lynch, William E. ; Reibman, Amy R. ; Liu, Bede
Author_Institution :
Dept. of Electr. & Comput. Eng., Concordia Univ., Montreal, Que., Canada
Abstract :
Discrete cosine transform coding, a popular image compression strategy, results in two visible artifacts: blocking and ringing. These are both high frequency artifacts. Since images contain high frequency information the artifacts are removed using a space varying low pass filter as a post processor. Low frequency blocks and flat regions of blocks containing a strong edge are filtered. Low frequency blocks are identified in the transform coefficient domain; edge blocks are identified in the spatial domain. This does not require any alterations in the compressed bit stream. Improvement is demonstrated both subjectively and objectively
Keywords :
data compression; discrete cosine transforms; filtering theory; image coding; low-pass filters; transform coding; DCT; blocking; compressed bit stream; discrete cosine transform; edge blocks; flat regions; high frequency artifacts; high frequency information; image compression; low frequency blocks; objective results; post processing; post processor; ringing; space varying low pass filter; spatial domain; subjective results; transform coded images; transform coding; transform coefficient domain; Attenuation; Discrete cosine transforms; Discrete transforms; Filtering; Frequency; Image coding; Image reconstruction; Low pass filters; Nonlinear filters; Streaming media; Transform coding;
Conference_Titel :
Acoustics, Speech, and Signal Processing, 1995. ICASSP-95., 1995 International Conference on
Conference_Location :
Detroit, MI
Print_ISBN :
0-7803-2431-5
DOI :
10.1109/ICASSP.1995.479957
