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

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