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jpeg2000 Allows 200:1 Wavelet Compression

Posted by Roblimo on from the another-potential-GIF-alternative dept.

Polo writes "Here is an EE times article about the ISO JPEG2000 standard that has been finalized and allows a new wavelet compression scheme that gives good results at as much as 200:1 compression ratios. It looks pretty promising. It is royalty-free, but there is also discussion about a second standard that allows third-party, royalty-based extensions. I wonder if motion-jpeg with wavelets could fit a movie on a CD or something."

1 of 241 comments (clear)

  1. About time... by Oestergaard · · Score: 5

    That was pretty much about time someone took the wavelets into image compression.

    I worked with wavelet transforms (Daubechies wavelets) a year and a half ago, and back then it was pretty clear that it would be possible to compress images and sound much harder using the wavelet domain rather than the Fourier domain.

    For those who don't know, the trick is:
    JPEG/MPEG/MP3 uses Fourier transform to transform the image/sound data into their spectral components. But this spectral representation of the data does not say anything about the _locality_ of the frequency components. Therefore representing spikes/discontinuties will require a very large number of frequency components when using Fourier domain, which in turn leads to poor compression. You can see this problem by drawing a few sharp lines in an image and compressing it hard with JPEG.

    Wavelets on the other hand, represent both an equivalent of the frequency component, along with locality information. Spikes/discontinuities can be approximated well using only a few wavelets. This in turn leads to good compression.

    Another nice thing about wavelet compression is, that wavelets tend to represent discontinuities well, even with hard compression (eg. a lot of missing or roughly approximated wavelet components). Therefore a very hard compressed image will still have fairly sharp edges, completely contrary to JPEG compression. This is pretty important if you compress a picture holding text.

    Anyways, someone is now working on JPEG with wavelets... What about sound and video ?? There is no reason as to why wavelets should not provide equal improvements in both audio and video.

    My personal conspiracy theory is, that there exists a *LOT* of expensive hardware that can do Fouries forwards and back to allow real-time encoding and decoding of MPEG movies in good quality. The companies producing these devices will lobby any standards-organisation to *NOT* consider wavelets and stick to good old Fourier. If this holds, it will take a few years until we see Wavelet compressed video :)