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Old 18th January 2012, 03:16 PM   #1
benb is offline benb  United States
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Default FFT, now even faster

The faster-than-fast Fourier transform

For a large range of practically useful cases, MIT researchers find a way to increase the speed of one of the most important algorithms in the information sciences.

http://web.mit.edu/newsoffice/2012/f...orms-0118.html

... but it's still not faster than the speed of light.
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Old 18th January 2012, 06:26 PM   #2
Pano is offline Pano  United States
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Hmmmm.......
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Old 18th January 2012, 09:45 PM   #3
DF96 is offline DF96  England
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MIT is full of clever people, so we can assume the developers of this method are smarter than the PR man who wrote the linked piece. He seems to think that chamber music is 'sparse' - maybe sparser than a full orchestra, but I wouldn't want to hear a quartet replaced by a few gated sine waves!
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Old 18th January 2012, 09:56 PM   #4
jcx is online now jcx  United States
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well the practical lesson from perceptual audio compression is that you can get quite "transparent" music reproduction from <20% of RedBook Shannon-Hartley Channel Capacity bit rate - so "sparse" could be a fair characterization for music

the compression algorithms currently used in audio have a harder time with the broadband noise of the audience applause
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Old 18th January 2012, 10:12 PM   #5
DF96 is offline DF96  England
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I remember some years ago listening to Classic FM on DAB (MP2 coding at 160 kbit/s). The music was tolerable, but the applause at the end sounded just like someone varying the level of a white noise generator. Horrible! I switched back to FM and that was fine. Not long after that I stopped listening to DAB.
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Old 18th January 2012, 10:24 PM   #6
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I often hear MP3-style compression in cymbals; stuff that is noise-like, but not actually noise, and your brain can spot the structure even if the compression algorithm can't. You can also see the same thing in MPEG'ed video, where 'noise-like' scenes reveal the edges of the DCT-ed blocks. I particularly notice it on crowd scenes and the surface of rough water.
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Old 18th January 2012, 10:36 PM   #7
DF96 is offline DF96  England
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A camera pan during football makes the blades of grass disappear on digital TV - looks like a billiard table instead. Once the camera stops moving the grass reappears.
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Old 19th January 2012, 12:20 AM   #8
a.wayne is offline a.wayne  United States
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When ... during the WC ? Too much Stout + England's drubbing ....
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Old 19th January 2012, 01:12 AM   #9
benb is offline benb  United States
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Quote:
Originally Posted by DF96 View Post
MIT is full of clever people, so we can assume the developers of this method are smarter than the PR man who wrote the linked piece. He seems to think that chamber music is 'sparse' - maybe sparser than a full orchestra, but I wouldn't want to hear a quartet replaced by a few gated sine waves!
Quote:
Originally Posted by jcx View Post
well the practical lesson from perceptual audio compression is that you can get quite "transparent" music reproduction from <20% of RedBook Shannon-Hartley Channel Capacity bit rate - so "sparse" could be a fair characterization for music

the compression algorithms currently used in audio have a harder time with the broadband noise of the audience applause
Yeah, reading the article, it seems like it's the same old MP3 type encoding being used for more things. The writer does seem to think a string quartet is just four sine waves.

The more I read, the less "new" this sounds. The Goertzel Algorithm is just a digital filter calculation to do a single FFT bin, and this talks about doing fewer FFT binss, but you still have to do a full FFT at the start to know what bins have "almost" no signal so they can be (possibly) ignored.

As I've seen pointed out before, with "digital" we don't get The Miracle Of No Distortion, we get different and never-before-heard distortions.
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Old 19th January 2012, 05:21 AM   #10
ontoaba is offline ontoaba  Indonesia
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Quote:
Originally Posted by CopperTop View Post
I often hear MP3-style compression in cymbals; stuff that is noise-like, but not actually noise, and your brain can spot the structure even if the compression algorithm can't. You can also see the same thing in MPEG'ed video, where 'noise-like' scenes reveal the edges of the DCT-ed blocks. I particularly notice it on crowd scenes and the surface of rough water.
128kBps MP3 is not CD quality, I could still clearly easy to hear the differences with 192kBps version. If I converting CDs, I use 320kBps, space isn't problem for this days storage system. Compression logarithm couldn't keep its fast changes properly.
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