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CD-R and Audio Hardware => CD Hardware/Software => Topic started by: donlombardo on 2021-01-29 07:21:46

Title: EAC CD Drive offset 3 CD verification - How does it work?
Post by: donlombardo on 2021-01-29 07:21:46
Hello! I am, as a hobby project, trying to make a CD drive offset calculator for linux, that works without wine. My question is: how does the drive offset calculator actually work in EAC? It uses AccurateRip, but how?

Couldn't find anything on the net when googling, but I'm sure someone here can either point me in the right direction or explain to me how (verbosely please).
Title: Re: EAC CD Drive offset 3 CD verification - How does it work?
Post by: korth on 2021-01-29 14:17:07
You should probably try asking in illustrate's forum (https://forum.dbpoweramp.com/forumdisplay.php?54-CD-Ripper).
3 CD verification (requires 3 key discs (http://www.accuraterip.com/keydiscs.htm) when a drive doesn't exist in or was purged from (for not having a constant drive offset) the drive offset database (http://www.accuraterip.com/driveoffsets.htm)) comes from the illustrate AccurateRip plugin (AccurateRip.dll) not EAC.
It usually only requires 1 key disc to verify the offset. The CRC from a small sample of each track is compared to the key disc (or discs) in the database then compared to the drive offset database. I can't tell you how many samples or where in the track the CRC is calculated from.
Quote
Finding Offset for E:\   [TSSTcorp - CDDVDW SH-224DB ] - 10 Tracks    [FreedB  7d088b0a,  Added  000d9178,   Multi  006cd59f]


  Track 1 - CRC matching b25ff4a3 [confidence 19]
  Track 1 - CRC matching 621acff4 [confidence 11]
  Track 1 - CRC matching 470f7c7f [confidence 9]
  Track 1 - CRC matching 00000000 [confidence 8]
  Track 1 - CRC matching 00000000 [confidence 7]
  Track 1 - CRC matching 00000000 [confidence 5]
      Offset match at 6 samples (24 bytes)
      Offset match at -15 samples (-60 bytes)
      Offset match at 239 samples (956 bytes)

  Track 2 - CRC matching f06bb250 [confidence 18]
  Track 2 - CRC matching 7c457798 [confidence 12]
  Track 2 - CRC matching eb1e9ec5 [confidence 9]
  Track 2 - CRC matching 00000000 [confidence 9]
  Track 2 - CRC matching 00000000 [confidence 7]
  Track 2 - CRC matching 00000000 [confidence 5]
      Offset match at 6 samples (24 bytes)
      Offset match at -15 samples (-60 bytes)
      Offset match at 239 samples (956 bytes)

  Track 3 - CRC matching 0776e4f0 [confidence 19]
  Track 3 - CRC matching 90d9b9fa [confidence 11]
  Track 3 - CRC matching 491acd34 [confidence 9]
  Track 3 - CRC matching 00000000 [confidence 8]
  Track 3 - CRC matching 00000000 [confidence 7]
  Track 3 - CRC matching 00000000 [confidence 5]
      Offset match at 6 samples (24 bytes)
      Offset match at -15 samples (-60 bytes)
      Offset match at 239 samples (956 bytes)

  Track 4 - CRC matching b4f3cc8c [confidence 19]
  Track 4 - CRC matching 318b6038 [confidence 11]
  Track 4 - CRC matching 0ad46a48 [confidence 8]
  Track 4 - CRC matching 00000000 [confidence 8]
  Track 4 - CRC matching 00000000 [confidence 7]
  Track 4 - CRC matching 00000000 [confidence 5]
      Offset match at 6 samples (24 bytes)
      Offset match at -15 samples (-60 bytes)
      Offset match at 239 samples (956 bytes)

  Track 5 - CRC matching 6bab55f1 [confidence 19]
  Track 5 - CRC matching 6f9c8e34 [confidence 11]
  Track 5 - CRC matching 678084a6 [confidence 9]
  Track 5 - CRC matching 00000000 [confidence 8]
  Track 5 - CRC matching 00000000 [confidence 7]
  Track 5 - CRC matching 00000000 [confidence 5]
      Offset match at 6 samples (24 bytes)
      Offset match at -15 samples (-60 bytes)
      Offset match at 239 samples (956 bytes)

  Track 6 - CRC matching 4d904dad [confidence 19]
  Track 6 - CRC matching 06b9404f [confidence 11]
  Track 6 - CRC matching d2497b4d [confidence 9]
  Track 6 - CRC matching 00000000 [confidence 9]
  Track 6 - CRC matching 00000000 [confidence 7]
  Track 6 - CRC matching 00000000 [confidence 5]
      Offset match at 6 samples (24 bytes)
      Offset match at -15 samples (-60 bytes)
      Offset match at 239 samples (956 bytes)

  Track 7 - CRC matching eff7d5bf [confidence 19]
  Track 7 - CRC matching 260292e8 [confidence 11]
  Track 7 - CRC matching 417c9db4 [confidence 9]
  Track 7 - CRC matching 00000000 [confidence 9]
  Track 7 - CRC matching 00000000 [confidence 7]
  Track 7 - CRC matching 00000000 [confidence 4]
      Offset match at 6 samples (24 bytes)
      Offset match at -15 samples (-60 bytes)
      Offset match at 239 samples (956 bytes)

  Track 8 - CRC matching 8b6a65e6 [confidence 19]
  Track 8 - CRC matching e2c8f984 [confidence 12]
  Track 8 - CRC matching cc23f1a1 [confidence 9]
  Track 8 - CRC matching 00000000 [confidence 9]
  Track 8 - CRC matching 00000000 [confidence 7]
  Track 8 - CRC matching 00000000 [confidence 5]
      Offset match at 6 samples (24 bytes)
      Offset match at -15 samples (-60 bytes)
      Offset match at 239 samples (956 bytes)

  Track 9 - CRC matching 8ff9f0ee [confidence 18]
  Track 9 - CRC matching 00034f00 [confidence 12]
  Track 9 - CRC matching 0ac157cd [confidence 9]
  Track 9 - CRC matching 00000000 [confidence 9]
  Track 9 - CRC matching 00000000 [confidence 7]
  Track 9 - CRC matching 00000000 [confidence 6]
      Offset match at 6 samples (24 bytes)
      Offset match at -15 samples (-60 bytes)
      Offset match at 239 samples (956 bytes)

  Track 10 - CRC matching 92f56816 [confidence 18]
  Track 10 - CRC matching 2ef22c61 [confidence 11]
  Track 10 - CRC matching ff065085 [confidence 8]
  Track 10 - CRC matching 00000000 [confidence 8]
  Track 10 - CRC matching 00000000 [confidence 7]
  Track 10 - CRC matching 00000000 [confidence 5]
      Offset match at 6 samples (24 bytes)
      Offset match at -15 samples (-60 bytes)
      Offset match at 239 samples (956 bytes)
Match from Drive Database


Congratulations, AccurateRip has been set up correctly. It is recommended that this disc is ripped to test the accuracy of your drive. Calculated offset value: +6 samples, +24 bytes.

I don't know the address for the database the 'Detect read sample offset correction' button in EAC uses but it doesn't find the disc used above.

Title: Re: EAC CD Drive offset 3 CD verification - How does it work?
Post by: donlombardo on 2021-02-03 19:18:47
Thank you for your reply! I will continue investigating this :)
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