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March 2005
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2005.04.01 08:08 "Re: tif_jpeg.c and 12bit JPEG Files", by Jean-yves Le Ridant
Hello Bob, Tuesday, March 29, 2005, 6:08:24 PM, you wrote: > To me, the 16-bit JSAMPLE is really only a performance impact for > 8-bit users who expect to memcpy() directly to and from libjpeg's > buffers. Applications which iterate through the JSAMPLE array in > order to copy to/from their own format should see little performance > difference. I'm currently, downloading-installing cygwin's tiff and jpeg material, - I was'nt aware ... :-((( - and getting a global survey of differences of both tiffwin32, cygwin tiff and jpeg, from 'pure' libtiff et v6b. At this point, so not knowning what is exactely done in each case, I also have great doubt about real impact of "few and long" memcpys vs iterations in a general case, and especially when writing files. The more side effect I imagine, if for writers processing 'big' tile(s), ( temp alloc of rawsize * 2 and optimized hufftbl per jpeg frame ) and eventual .... system bootleneck. "comme on dit ici". The optimized two pass mode imposed ( at runtime ) to 12 bits samples in ijgv6b can safely be inhibited. I had the use of such practice ... it worked with 12 bits chunck ... choosen ... in study case :-) -- Jean-Yves