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jpeg2000 compression: window size?
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| franco.woolfe@gmail.com 2006-04-28, 7:55 am |
| Hi
The jpeg2000 compression format works by
1. splitting the image into disjoint rectangles and
2. applying a discrete wavelet transform to each rectangle.
The size of the rectangles can be chosen -- jpeg2000 doesn't specify
it. Does any one know
a. What are typical rectangle sizes used?
b. What are the respective advantages or di vantages of larger or
smaller rectangle sizes?
Thanks!
PS a good review article is
The JPEG2000 still image coding system: an overview
Christopoulos, C.; Skodras, A.; Ebrahimi, T.;
Consumer Electronics, IEEE Transactions on
Volume 46, Issue 4, Nov. 2000 Page(s):1103 - 1127
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| Thomas Richter 2006-04-28, 6:55 pm |
| Hi,
> The jpeg2000 compression format works by
> 1. splitting the image into disjoint rectangles and
> 2. applying a discrete wavelet transform to each rectangle.
Actually, the best way to go is to *avoid* these rectangles and
encode the full image at once. They're called "tiles".
> The size of the rectangles can be chosen -- jpeg2000 doesn't specify
> it. Does any one know
> a. What are typical rectangle sizes used?
One tile, as large as the image.
> b. What are the respective advantages or divantages of larger or
> smaller rectangle sizes?
Since the wavelet transformation is interrupted at tile boundaries,
you get artifacts there and thus see tile boundaries especially at
lower bitrates. The advantage might be that - at least for a lazy
coding design - you only need to buffer the image data for at most
one tile.
So long,
Thomas
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