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This archive contains a quick & dirty implementation of the IEEE Standard
1180-1990 accuracy test for inverse DCT. It is not guaranteed to be
correct ... but if you find any bugs, please let me know (by email to
tgl@cs.cmu.edu).
The test harness consists of the C program ieeetest.c and shell script
doieee. For comparison purposes I have also supplied a copy of jrevdct.c,
the inverse DCT routine from release 4 of the Independent JPEG Group's
free JPEG software. (jrevdct.c is slightly modified from the IJG release
so that it will compile without the IJG include files.) jrevdct.c passes
the 1180 test --- or at least, this program thinks so. jrevdct.out is
the output from a test run.
Note that numerical results may vary somewhat across machines. This appears
to be mostly due to differing results from the cosine function.
INSTALLATION:
Check the Makefile, change CC and CFLAGS if needed. Then say "make".
If your C compiler is non-ANSI, you may need to change includes and/or
function headers.
To test a different IDCT routine, link with that routine instead of
jrevdct.o. You will need to modify dct.h and/or ieeetest.c if your
routine's calling convention is not in-place modification of an array
of 64 "short"s.
USAGE:
The standard test procedure is
doieee ieeetest >outputfile
Expect it to take a while (almost 80 minutes on my old 68030 box).
Each of the six passes will emit a row of 100 dots as it runs.
You can grep the output for the word FAILS if you just want to know
yea or nay.
LEGAL MUMBO-JUMBO:
I hereby release the test harness to the public domain.
Thomas G. Lane, 22 Nov 1993
IMPORTANT: jrevdct.c is NOT public domain, but is copyrighted free software
(not the same thing at all). It is subject to IJG's distribution terms, which
primarily state that if you incorporate it into a program you must acknowledge
IJG's contribution in your program documentation. For more details and the
complete IJG software, see the IJG FTP archive at ftp.uu.net, in directory
/graphics/jpeg.
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