2005.03.22 17:20 "[Tiff] tif_jpeg.c and 12bit JPEG Files", by Frank
Warmerdam
Thread
2005.04.01 08:08 "Re[3]: [Tiff] tif_jpeg.c and 12bit JPEG Files", by Jean-Yves Le Ridant
Hello Bob,
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