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How does your computer identify a cd you insert?

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How does your computer identify a cd you insert?

Old 10-13-05, 01:32 PM
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How does your computer identify a cd you insert?

I kind of wondered about this. I know it connects to a DB online, but how does it match info? Is there a header file on the CD somehow? Does it Match CD and Track lenghth time wise?

Anyone know?
Old 10-13-05, 01:54 PM
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I believe it searches according to the title of the CD, which is why sometimes you might get a window asking which CD you are listening to, because there are multiple entries with a similar title.
Old 10-13-05, 02:18 PM
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^ No, only way it could do that if the disc had CD-TEXT and the vast majority of releases do not.

I believe that it's an agorithm based on the # of tracks, length of each track and total length of the CD. However, I don't know the specifications of the algorithm.

-- Jim
Old 10-13-05, 03:01 PM
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To store all that information in a useful way, each CD needs a unique identifier in the CDDB database. Before I started poking around a little, I assumed that each CD was burned with a unique key parcelled out by an agency like ISBNs for books. What actually happens is when the information from a CD is placed in the CDDB for the first time, the CD's TOC is stored in the database as the identifier for that CD. The TOC contains the lengths of all the tracks as well as the starting sectors of each track. That means that TOC is not necessarily unique...it's merely almost unique, causing the occasional misidentification.
TOC = Table of Contents

http://www.kottke.org/02/07/the-compact-disk-database

Last edited by Numanoid; 10-13-05 at 03:03 PM.

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