[Tig] video compression: lossless? (JPEG2000) (Rob Lingelbach)

Bob Friesenhahn bfriesen at simple.dallas.tx.us
Mon Oct 19 17:34:23 BST 2009


On Mon, 19 Oct 2009, Richard Kirk wrote:
>
> A bit more than 2x compression may not sound much, but it is more than YCrCb 
> encoding, and it does a lot less damage.

People have been using YCbCr video for so long now that they have 
forgotten that it is a form of compression, even at "4:4:4".  The 
whole TV video chain uses various forms of crude compression at each 
step of the way before any "compressor" is applied.

   pixelization   = compression
   quantization   = compression
   YCbCr          = compression
   subsampling    = compression
   gamma encoding = compression

The main problem with compressors like JPEG2000 is that they are very 
slow to do in software and there are patent issues.

I continue to hope that the original IJG JPEG library will be updated 
to support 8/12/16 bits in the same build so that old-fashioned JPEG 
can be used for faster compression with more precision.  There have 
been recent quality improvements in this library but the maintainer is 
currently working on advanced DCT technology rather than 
multiple-depth enhancements.

Bob
--
Bob Friesenhahn
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/




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