[Tig] video compression: lossless? (JPEG2000)
bfriesen at simple.dallas.tx.us
Sat Oct 17 21:54:32 BST 2009
On Sat, 17 Oct 2009, Rob Lingelbach wrote:
> When a manufacturer claims lossless video compression, do we understand it as
> being theoretical, and rarely used, as a practical matter?
> I ask because I got into this discussion with a friend who claimed that he
> was seeing lossless compression in satellite program transmissions due to
> JPEG2000 being used. According to what I understand about JPEG2000, it
> depends how it is scaled, but there are also some complex questions about the
> wavelet transform, and subsequent quantization, which is lossy (according to
> my understanding which may not be complete). I would like to try to clarify
> this with those in the know.
JPEG2000 does support a lossless mode. I am not sure how JPEG2000
works, but it is worth noting that it is possible to accomplish
lossless compression by using a lossy compressor in conjunction with
the difference data necessary to achieve lossless results. This works
since the difference (error) is much smaller than the original data.
You can play with JPEG2000 via GraphicsMagick.
bfriesen at simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/
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