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Topic: XLD C2 producing AccurateRip inconsistencies (Read 4560 times) previous topic - next topic
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XLD C2 producing AccurateRip inconsistencies

This is my first post.

When using [XLD Secure Ripper] mode in combination with [Use C2 error pointers] and [Query AccurateRip database to check integrity], I get this strange behaviour:
  • Without C2 it is all fine. I get AccurateRip Summary: all tracks accurate [AccurateRip confidence: 43/288 - 34/269]. Checking [Test before copy] and [Verify suspicious sectors] give the same results. I get 0 Retry sector count and 0 Jitter error for all tracks. (BTW: Using Burst mode also gives the same AccurateRip results.
  • With C2 only about 30% (this seems to gets worse as drive gets hotter) of the tracks get the "AccurateRip OK" approval, the other tracks are marked NG and get the 'Rip may not be accurate' message. Those NG tracks show a 'Retry sector count' of >1000 and 'Jitter error (maybe fixed)' of 1 or higher.


I've been reading up on C2 and all for a few days now.

My conclusion is that the C2 error pointers point to errors that already have been corrected by the players hardware system. That's why in burst mode it says AccurateRip OK. But when trying to re-read those C2 error corrected sectors, the player produces jitter errors which are not accurately fixed by XLD and make it to the resulting file, thus producing a different checksum, resulting in AccurateRip NG.

This is my thought process:
  • The player of my MBP 17" (MATISHA DVD-R UJ-898 (rev HC09) reads the CD in burst mode and corrects errors using the correct C1 and C2 hardware error correction. However: For error it outputs a C2 error flag, while some might be corrected, some might not be corrected. For errors that can't be corrected it's up to the software concealment circuit to determine whether to output the data directly, to interpolate it, or to mute the output. But the player also gives C2 error pointers for read errors that have been corrected by the error correction.
  • XLD uses these error pointers to check if the error is corrected or should be concealed. It does this by re-reading those sectors that have error pointer. In case a statistically consistent result was found with the retry reads, this count is incremented.
  • When re-reading the drive produces jitter-errors. The error occurs when seeking between sectors back and forward heavily - the drive fails to return the accurate sector position and returns a slightly moved position. XLD will try to fix this, but something goes wrong.
  • Because of this the AccurateRip checksum is inconsistent and I get the NG message.


Could this be correct?

sources:
http://www.hydrogenaud.io/forums/index.php?showtopic=84992
http://www.hydrogenaud.io/forums/index.php?showtopic=106153
https://books.google.nl/books?id=Ed388jKoOfQC&pg=PA65
https://dbpoweramp.com/spoons-audio-guide-cd-ripping.htm

XLD C2 producing AccurateRip inconsistencies

Reply #1 –
Jitter has only been a problem on CD drives from a good 15 years ago. These days all drives are AccurateStream which are jitter resistant.

That is not to say that enabling c2 pointers on some drives might expose bugs in the drive its self or in the ripping program.

XLD C2 producing AccurateRip inconsistencies

Reply #2 –
Knowing nothing about the C2 pointer feature in XLD, my takeaway is that it shouldn't be used with this specific drive rather than condemning its use with all drives.  Of course my position is largely influenced by my involvement in discussions over a different ripping program.

XLD C2 producing AccurateRip inconsistencies

Reply #3 –
using dbpoweramp across several drives I can report that some drives handle C2 errors very well and some choke when trying to use C2. And this seems unrelated to age of drive or brand in my limited set of comparisons.

XLD C2 producing AccurateRip inconsistencies

Reply #4 –
Thanks for your replies. I agree with you this thread should be about my specific cd reader model only.

As I see it the c2 error pointers only flag sectors for re-reading. The C2 flag do not produce the read errors, as burst mode checks out fine with AccurateRip. It is the XLD re-read that produces the jitter errors resulting in AccurateRip inconsistencies.

Apparently AccurateStream doesn't work well for my particular combination of cd reader and XLD software?

XLD C2 producing AccurateRip inconsistencies

Reply #5 –
From http://tmkk.undo.jp/xld/index_e.html:
Quote
Added option to use C2 error pointers
When the option is turned on, XLD first read a sector in burst mode, and check the occurrence of C2 error. If C2 error occurs, then XLD re-read the sector with cdparanoia. This accelerates ripping extremely for the drive with C2 error support (Plextor, NEC, etc), without losing safety. If you use this option, please make sure that your drive supports reporting C2 errors.

It looks C2 pointers are used in the same way as they are used in EAC.  So unless there is some additional undisclosed magical sauce (additional means to verify that C2 errors didn't go unreported by the drive), the "without losing safety" quoted above would appear to be bullshit.  Seeing as though people are attaining burst speeds with the C2 pointer feature enabled, the only additional means that I can see would be a reliance on an online database such as AR.

XLD C2 producing AccurateRip inconsistencies

Reply #6 –
I tried rereading your reply but i don't see how that is an answer to my questions?