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Peter Creasey
September 13th, 2007, 08:44 AM
This is not for the faint of heart (or mathematically challenged)...

JPEG Compression Article (http://www.ams.org/featurecolumn/archive/image-compression.html)


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MollyM/CA
September 13th, 2007, 07:23 PM
This is not for the faint of heart (or mathematically challenged)...

JPEG Compression Article (http://www.ams.org/featurecolumn/archive/image-compression.html)


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There's one for TIFF somewhere too. What you said, not for the... I got the link from Desktop Publishing Forum -- might be able to hunt it down if anyone wants to know.

MP3 compression for audio is like JPG in that it's lossy -- there's a wonderful alternative compression called FLAC that is economical as to space and non-lossy. You can read about it at

http://flac.sourceforge.net/

Not every player can play FLAC files. The site explains it, sort of (not for my fuzzy head; I got the plug-in for CoolEdit). I found out about FLAC from a site that has several of my composer friend Ezra Sims' pieces:

http://www.avantgardeproject.org/archive.htm

The archive is added to every day and I notice that "avante garde" is getting broader all the time -- Hindemith and Mort Subotnick and Takemitsu and whale songs as well as John Cage and Harry Partch and other icons of the further-than-everyone.

jdh
September 13th, 2007, 11:56 PM
Not every player can play FLAC files.

I'm a trailing edge kind of guy. My portable CD player only handles MP3 and WMA compressed audio. Are you talking about plugins / codecs for software application based multimedia players for PC's ? (Of course, that's probably technically misleading since I'd be almost certain that my portable CD player decompression is software based too, although I suppose there might be some dedicated hardware optimization used during decompression?).

David H

Andrew B.
September 14th, 2007, 01:23 AM
Thanks. Even ignoring the math, this is still very helpful. It explains a lot of what I've been wondering about.

MollyM/CA
September 14th, 2007, 05:47 PM
Here's what the Avant Garde Project site says:

he audio files in all AGP installments are FLAC files. FLAC is a lossless compression format that decompresses to produce CD-quality WAV files. MP3 files, by contrast, preserve a decent amount of the sound in a recording, but lose the low-level detail that gives it realism. The difference is plain even on moderately priced equipment.

Further information on FLAC (Free Lossless Audio Codec) and free downloads of the FLAC coding/decoding software can be found on the Sourceforge FLAC web site. This software has a very simple, intuitive interface, and will enable you to produce WAV files that can be burned to an audio CD. You can also download plugins that will enable you to play FLAC files directly in Winamp or Foobar2000.

I found links to a tweak for Media Player (and commented 'extremely tedious' when I sent it on to Ezra)

Media Player Tweak (http://www.losslessaudioblog.com/wmpmce-lossless-guide/)

and he somehow became able to play his downloaded FLAC files. (If you wonder why a composer would want to download his own music: to compare the downloads to the originals on the out-of-print CDs, which of course he has copies of.) I don't use Media Player except when I'm sent a file nothing else will handle, so don't understand just what he did. If you want to burn a FLAC file to a CD you have to convert it to WAV or MP3. I'm seeing a few references to FLAC here and there, and there are murmurs about being able to play FLAC files directly on an iPod (Google FLAC), which would be nice. The quality of the few files I downloaded was very very good -- I don't find MP3 up to a good symphonic recording with the good headphones -- therefore don't think it's good enough for me on the car stereo either.

Back to the JPEG article, I think I got the idea even though my mind goes blank when I see "cosine" on a page, between the good illustrations and really simple stuff in between the math and tables (not for the likes of me). Great link.

fhaber
September 15th, 2007, 12:30 PM
Good visual + math overview. The following story will reveal more than I want of the geekiness at my core:

When I first read about the spatial and perceptual tricks of JPEG, I was impressed.

When I first encountered motion-JPEG, with its looking forward and backward in time (the better to compress), I experienced an epiphany. I think I overreacted.

"Dammit - there's a TIME MACHINE in every DVD! It's science fiction!" Then I remembered an aphorism recited to me about 1980, in the early days of digital audio. "No digital audio scheme worth having could ever remotely be considered real-time."

I snapped out of it. Delay is the balm that soothed my Newtonian jitters.