Quote:
Originally posted by Halcyon
Eh? I don't understand.
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When an error occurs, the C1 and C2 processes can recover exactly the info. This occurs inside the drive, and can't be accessed from outside.
The only thing viewable from outside is the C2 flag, that is 'right' or 'wrong'.
'Right' means that either there was no error, either there was a perfectly corrected error.
'Wrong' means that the C2 info couldn't be used to reconstruct the missing data.
From here, the processes of audio playback and audio extraction differs.
Audio extraction stops there, and a wrong data is returned.
Audio playback then perform "error concealment" : wrong data are interpolated from neighborous valid samples. That's why in most cases, a scratched CD clicks when extracted, and doesn't when played.
EAC beta is the first soft that tries to simulate the error concealment, that is missing on the hard side, in the soft side. It interpolates the data when the C2 info says that an error wasn't recovered.
Andre could explain better, but I guess that isn't not very efficient yet, because it must just perform a regular "deglitch" process when a C2 error is returned, instead of searching for the nearest neighborous valid samples and interpolate.
That's why the test CD comments don't apply : error concealment is part of the required specs to play an audio CD. Therefore if they took that into account, a Digital Audio Extraction can clic while the drive performs as well as an audio player that doesn't click (thanks to error concealment).
Quote:
Originally posted by Halcyon
3) 'It's not perfectly implemented yet'? Does this mean that the C2 usage inside EAC is not ACCURATE yet, even if the player returns totally accurate C2 data 100% of the time? If so, is there *any* reasong to use C2 features in the current version?
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I mean that a regular deglitch must be run on C2 error instead of a real emulation of error concealment, leading to low quality error concealment. Is it right Andre ? I though I heard deglitch artifacts when listening to a double C2 corrected wav from a scratched CD.
Quote:
Originally posted by Halcyon
This is *exactly* what I did with my test cd:
1) On plextor I get some read errors (due to errors on test disc), but the copy if finished OK according to EAC (the errors are corrected). The ripped tracks sound totally flawless.
2) On hitachi I get same read errors AND the copy is NOT finished OK according to EAC. The ripped tracks sound glitchy and problematic (all of the test track of increasing difficulty).
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That doesn't tell if C2 works well. The point is to "test and copy selected tracks", not to "copy". Then the test CRC and read CRC are displayed, and in the CRC column, "OK" means that the CRC match : the copy is OK, and "#" means that the CRC don't match : there were errors. Then you can compare these reports to the log window. A high number of C2 errors resulting in "copy OK",
then confirmed with CRC OK is the secure way to test C2 accuracy.
The fact that the wavs sound perfect is no proof. The C2 problems with the Hitachi GD-7500 are in fact completely unaudible. The errors don't go higher than two or four elementary steps (I cut and inverted-pasted the wavs) that is -84 or -90 db !
Quote:
Originally posted by Halcyon
I think GD-7500 probably returns some totally inaccurate C2 data all the time.
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That's not the case for me. It really starts error correction each time a scratch is encountered.
It seems to be accurate 90 (for the 'wrong' reports) to 99.999999 % ('right' reports) of the time.
Quote:
Originally posted by Halcyon
Impossible? Damn... I was hoping there was some accurate way to detect at least the reader's gap detection accuracy.
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The point was that the index number is written at given time intervals in the subcode channel, and that this subcode channel can be used for other infos. EAC searches for the point where the index number changes. If some other info replaces the index number right on the transition, then the transition can't be defined with accuracy.
Example :
000001111
The gap is 5 steps long.
0xxxxxx111
The gap is between 1 and 7 steps long.
I don't know how long are the steps, nor how long the subcode channel can be used by other infos.
Quote:
Originally posted by Halcyon
1. What dvd-rom drive (I need dvd) would be the safest to buy currently for audio extraction at maximum speed?
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No idea... But everybody's talking about Toshiba
Thanks for the interesting questions !