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Inconsistancies in physical CED contruction

 
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Caesius
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PostPosted: Wed Mar 16, 2005 3:12 pm    Post subject: Inconsistancies in physical CED contruction Reply with quote

In my search for additional CED information, I came upon a entry at
"http://en.wikipedia.org/wiki/CED". In the "How SelectaVision works" portion of the article a user wrote that CEDs stored its information in concentric grooves while the patent information information listed at www.cedmagic.com makes several references to CED information being stored as a sprial groove.

Needless to say, I am confused. How was the information stored on a CED: concentric or spiral tracks?
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cedmagic
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Joined: 11 May 2004
Posts: 335
Location: Portland, Oregon

PostPosted: Thu Mar 31, 2005 7:23 pm    Post subject: RE: Inconsistancies in physical CED contruction Reply with quote

Quote:
How was the information stored on a CED: concentric or spiral tracks?


I think the groove(s) on CED's can be considered concentric or spiral depending on whether you perceive the media from a electronic or mechanical perspective.

From a mechanical perspective, there is a single spiral groove on each side of a disc that begins at the outer edge and ends near the center.

But from an electronic perspective, an NTSC disc with 60 minutes of video on one side can be considered to have 27,000 concentric grooves corresponding to each rotation of the disc during playback. That's because the disc is split up like a pie into sectors corresponding to eight video fields per rotation, and between these field sectors are vertical blanking sectors containing Digital AuXiliary Information. This DAXI increments in such a way that any concentric groove on the disc can be numbered according to its DAXI contents.

--Tom Howe
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