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Thread View: comp.compression.research
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1 total messages Started by Rohit Agarwal Tue, 17 Nov 1992 01:03
( Shimmering ) artifacts in wavelet based video compression ?
#111
Author: Rohit Agarwal
Date: Tue, 17 Nov 1992 01:03
27 lines
2065 bytes
	I have been doing some work with the compression of video by taking
a wavelet transform, scalar quantization and entropy coding. I have implemented
a video compression scheme that uses purely spatial techniques. No motion info
is used. I applied my technique to the compression of several of the CCIR601
MPEG test sequences and observed the following:

	In some of the sequences, particularly Tennis and Flower Garden, there
was a noticable shimmering in the background. Viewed individually, each of the
frames looked very good. For Tennis and Flower Garden, PSNR was about 35 dB on
the average. However viewed as video, ther was a noticable shimmering artifact.
Its as if the errors in each frame are highly uncorrelated with errors in other
frames or maybe it has something to do with interlacing. It might also have 
been due to not using temporal information. I have seen some of the MPEG 2
results from Kurihama and I noticed that there were a few techniques based on
wavelets which did not seem to have these artifacts particularly Aware1 and
 Aware2.
Can anyone give me some pointers as to the possible sources of this artifact.
Interestingly enough, my technique did much better on Mobile and Calendar --
individual frames had a lower PSNR than the other test sequences (about 30 dB),
and there were noticable artifacts in the individual images viewed still (the
white background of the calendar looked dirty gray) but viewed as a sequence
it looked "pretty good" even at 1H.

Also, the compression ratio was only 20:1 translating to a bitstream of about
8Mbps. 

rohit agarwal
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