Fourier Transformation

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Fourier transformation is a technology used in different areas ... one of them is audio compression/storage. I found a nice page which contains an applet that allows you to experiment with this algorithm (using pictures instead of audio, but the principle is the same for any data, be it audio, video or images):

http://homepages.inf.ed.ac.uk/rbf/HIPR2/fftdemo.htm

The applet is a bit technical ... and of course this whole subject is. The reason for me posting this is that the applet shows that Fourier transformation really works ... and how it does its job. You'll see an image, you can perform Fourier transformation on the image and see the result, and you can perform the inverse Fourier transformation to put the image back together.

You can also have a look at this page which kind of gives you the "skinny" on Fourier transformation:

http://cns-alumni.bu.edu/~slehar/fourier/fourier.html

The high pass / low pass filters intrigued me, and you can test those with the applet and see the effects. 

Edited by MikeEnRegalia - May 28 2007 at 03:16

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MikeEnRegalia Members Profile Send Private Message Find Members Posts Add to Buddy List Reviewer page Special Collaborator Honorary Collaborator Joined: April 22 2005 Location: Sweden Status: Offline Points: 21106	Topic: Fourier Transformation Posted: May 28 2007 at 03:14
	Fourier transformation is a technology used in different areas ... one of them is audio compression/storage. I found a nice page which contains an applet that allows you to experiment with this algorithm (using pictures instead of audio, but the principle is the same for any data, be it audio, video or images): http://homepages.inf.ed.ac.uk/rbf/HIPR2/fftdemo.htm The applet is a bit technical ... and of course this whole subject is. The reason for me posting this is that the applet shows that Fourier transformation really works ... and how it does its job. You'll see an image, you can perform Fourier transformation on the image and see the result, and you can perform the inverse Fourier transformation to put the image back together. You can also have a look at this page which kind of gives you the "skinny" on Fourier transformation: http://cns-alumni.bu.edu/~slehar/fourier/fourier.html The high pass / low pass filters intrigued me, and you can test those with the applet and see the effects. Edited by MikeEnRegalia - May 28 2007 at 03:16
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Angelo Members Profile Send Private Message Find Members Posts Add to Buddy List Reviewer page Special Collaborator Honorary Collaborator / Retired Admin Joined: May 07 2006 Location: Italy Status: Offline Points: 13244	Posted: May 28 2007 at 16:52
	Interesting!!! When I was doing my graduation project, a PhD student in the department where I worked was working on image compression using Fourier transformations and some other mathematical operations. At some point he had a better compression rate then JPEG, and lossless as well. Pity that even on todays PCs his compression algorithm is still time consuming (this was almost 14 years ago).
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Dean Members Profile Send Private Message Find Members Posts Add to Buddy List Reviewer page Special Collaborator Retired Admin and Amateur Layabout Joined: May 13 2007 Location: Europe Status: Offline Points: 37575	Posted: June 07 2007 at 06:47
	A few years ago I wrote an Microsoft Excel module for computing FFT's. Excel is not the best tool for DSP, but I used it to demonstrate to a non-believer that clock-jitter affects the Signal-to-noise ratio of DAC converters. you can download the module from here: members.aol.com/deancr/tech/Module1.bas or the Excel spreadsheet with the module pre-loaded here: members.aol.com/deancr/tech/FFT.XLS
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