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Document the fact that the fast integer FDCT is not fully accelerated for quality levels above 97 + additional wordsmithing

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git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/branches/1.3.x@1289 632fc199-4ca6-4c93-a231-07263d6284db
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DRC
2014-05-11 23:14:43 +00:00
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@@ -176,11 +176,13 @@ With quality=97, for instance, the fast method incurs generally about a 1-3 dB
loss (in PSNR) relative to the int method, but this can be larger for some
images. Do not use the fast method with quality levels above 97. The
algorithm often degenerates at quality=98 and above and can actually produce a
more lossy image than if lower quality levels had been used.
more lossy image than if lower quality levels had been used. Also, in
libjpeg-turbo, the fast method is not fully accelerated for quality levels
above 97, so it will be slower than the int method.
.TP
.B \-dct float
Use floating-point DCT method.
The float method is mostly a legacy feature. It does not produce significantly
The float method is mainly a legacy feature. It does not produce significantly
more accurate results than the int method, and it is much slower. The float
method may also give different results on different machines due to varying
roundoff behavior, whereas the integer methods should give the same results on