[opendtv] Re: JPEG2000?
- From: "Manfredi, Albert E" <albert.e.manfredi@xxxxxxxxxx>
- To: <opendtv@xxxxxxxxxxxxx>
- Date: Fri, 14 Jul 2006 18:19:05 -0400
Cliff Benham wrote:
> The compression rate for JPEG2000 is incredible. An
> over 2 hour theatrical release takes only 250 G. All
> I frames, so no time fractured macro blocking.
JPEG2000 uses a wavelet transform vs discrete cosine transform, and it
offers a lot of flexibility, like scalability. But, as we saw on here in
previous threads from time to time, it doesn't seem to be any slam dunk
for compression efficiency, compared with alternatives. Or for
complexity in encoding and decoding.
This suggests that its use for motion pictures would not result in
better compression efficiency than M-JPEG, which of course is less good
(in that regard) than MPEG-2 (H.262). And less good than H.264, as well.
Here's an article that compares the coding efficiency of various
still-image codecs:
http://jj2000.epfl.ch/jj_publications/papers/004.pdf
The conclusions paragraphs say:
"The results presented in previous sections show that new standards do
not provide any truly substantial improvement in compression efficiency
and are significantly more complex
than JPEG, with the exception of JPEG-LS for lossless compression.
However, from a functionality point of view JPEG 2000 is a true
improvement, providing lossy and lossless compression, progressive and
parseable bitstreams, error resilience, random access, region of
interest and other features in one integrated algorithm.
"In any case the choice of a standard for a particular application or
product will depend on its requirements. JPEG-LS stands out as the best
option when only lossless compression is of interest, providing the best
compression efficiency at a low complexity. In the cases where lossy
compression is of interest and low complexity is of high priority JPEG
still provides a good solution. On the other hand JPEG 2000 provides the
most flexible solution, if the added complexity is acceptable. As for
MPEG-4 VTC, it appears to be of limited interest, except when the
ability to code arbitrary shaped objects is required."
As to the 250 GB storage for a 2 hour movie, using JPEG2000. I would
expect the result to be good for quality, and JPEG2000 is probably great
as a future-proof digital format in archives. But compared with a 2 hour
HDTV show, where HD uses every bit of the 19.39 Mb/s the entire time,
the MPEG-2 file would be just 17.45 GB.
So you're talking about over 14X the size of the MPEG-2 file. Depending
on how much greater the resolution of that JPEG2000 file was meant to
be, a 14X increase may or may not be impressive.
Bert
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