Mar 31 2010, 02:27
Joined: 16-October 03
Member No.: 9337
I have only now become aware of Gregory S. Chudov's effort to develop CTDB (CUETools DB). I am very excited about this as I have actually been suggesting this to spoon (dbpoweramp's developer for over 5 years)
for others that have missed it:
What's it for?
You probably heard about AccurateRip, a wonderfull database of CD rip checksums, which helps you make sure your CD rip is an exact copy of original CD. What it can tell you is how many other people got the same data when copying this CD. CUETools Database is an extension of this idea.
What are the advantages?
* The most important feature is the ability not only to detect, but also correct small amounts of errors that occured in the ripping process.
* It's free of the offset problems. You don't even need to set up offset correction for your CD drive to be able to verify and what's more important, submit rips to the database. Different pressings of the same CD are treated as the same disc by the database, it doesn't care.
* Verification results are easier to deal with. There are exactly three possible outcomes: rip is correct, rip contains correctable errors, rip is unknown (or contains errors beyond repair).
* If there's a match, you can be certain it's really a match, because in addition to recovery record database uses a well-known CRC32 checksum of the whole CD image (except for 10*588 offset samples in the first and last seconds of the disc). This checksum is used as a rip ID in CTDB.
What are the downsides and limitations?
* CUETools DB doesn't bother with tracks. Your rip as a whole is either good/correctable, or it isn't. If one of the tracks is damaged beyound repair, CTDB cannot tell which one.
* If your rip contains errors, verification/correction process will involve downloading about 200kb of data, which is much more than it takes for AccurateRp.
* Verification process is slower than with AR.
* Database was just born and at the moment contains much less CDs than AR.
How many errors can a rip contain and still be repairable?
* That depends. The best case scenario is when there's one continuous damaged area up to 30-40 sectors (about half a second) long.
* The worst case scenario is 4 non-continuous damaged sectors in (very) unlucky positions.
What information does the database contain per each submission?
* CD TOC (Table Of Contents), i.e. length of every track.
* Offset-finding checksum, i.e. small (16 byte) recovery record for a set of samples throughout the CD, which allows to detect the offset difference between the rip in database and your rip, even if your rip contains some errors.
* CRC32 of the whole disc (except for some leadin/leadout samples).
* Submission date, artist, title.
* 180kb recovery record, which is stored separately and accessed only when verifying a broken rip or repairing it.
May 27 2010, 20:15
Group: Super Moderator
Joined: 1-April 04
From: San Francisco
Member No.: 13167
Sorry but as there are no real FAQ or tutorial for AR & CTDB, the information is splitted everywhere.
Even if I am faulty, it is hard to follow all AR & CTDB subtilities. Sorry if I made you waste some time, but it was once again usefull to me to have an "unfriendly" discussion with you
Search for information before making claims and you should be ok. If you are unsure it is better to ask a question rather than speculate. It will result in far fewer incidents of being told you are not correct. This is advice I try to follow myself.
A while back I tried to split the discussions between CUERipper and CUETools. Now with CTDB, I feel more justified than ever with that decision. Even though they are linked to one another and are bundled together (which I think is a mistake), they each serve a specific purpose. Discussions are easier to follow when they are primarily focused on only one specific purpose. I don't think there are a lot of people who want to search through a discussion with hundreds of posts in order get information about something that doesn't show up until far into the discussion. If it weren't for this thread a lot of people would be asking, "WTF is CTDB? Where did this come from?". In fact this is exactly how this discussion got started. Wading through tons of logs with requests for clarification, requests for assistance with batch processing, feature requests, etc. with CUETools in order to find technical information about a ripping program is a nightmare. Anyhow, sorry for ranting.
This post has been edited by greynol: May 27 2010, 20:49
Reason for edit: Added quote
You cannot account for false negatives in sighted evaluations.
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