Quote:
Originally posted by Pio2001
How do we know if the drive doesn't miss some errors at higher error rates ?
These tests are very interesting for comparing the DAE ability of the drives, but the C2 results must be taken with caution.
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Hi Pio,
As you know I have some opinions on C2 accuracy and its relevance.
Two points,
1.
For most of us the high C2 error rates are not relevent. For high C2 error rates EAC is not likley to return an accurate rip and may indeed return a rip that has significant audible artifacts due to hold interpolation. If there is no other source for the CD some people (myself included) may resort to editing the resultant wave to improve its sound. In that case I doubt that inaccurate C2 reporting would make it that much worse and certainly no less accurate.
2.
Unless there is some elementary errors in the drive logic, what the C2 reporting actually shows is where the drive has detected an error (rightly or wrongly) and thus interpolated the signal. This will result in a wrong sample at that location unless the interpolation happens to independently produce the correct value (due to the nature of music there is a relatively high chance of this happening compared to a truly random signal). So from that perspective C2 is always correct. This could be tested by checking each C2 reported sample to see if it is interpolated.
The issue of C2 missing the detection of errors is quite different. In these cases, it is more that CIRC does not detect them due to either its own strategy or some other factors. If CIRC does not detect them they cannot be interpolated and the resultant wave will probably have audible clicks in it. Except for one single CD, I have only seem this happen on CDs with extreme damage where there were serious audible artifacts in the wave produced by large numbers of hold interpolations as well as single sample impulses.
From what I understand about how EAC works, the exact accuracy of C2 reporting is not important where large numbers of errrors occur as EAC relies on its reread process to determine the output wave. All that is necessary is for it to detect at least one error to start the reread process. I believe that C2 reporting should be able to provide this.
The situation is different for Plextools where C2 is more extensively used.
With the current tested performance of C2 reporting on drives equipped with the Mediatec chipsets (the fact that not all drives using these chipsets seem to have the same C2 reporting or CIRC performance tends to show that there are other factors involved in that performance), it is my hope that Andre will include some new C2 based secure modes similar to those used in Plextools so that we can take all of this out of the theoretical situation into a practical situation and do some real testing. I believe that the result will be more accurate rips (on damaged CDs) for some of these late CD drives.
Another addition I would like would be the inclusion of a C2 reporting file into EAC . This woiuld be the C2 information associated with the final written wave showing all interpolated samples. Such a file could be used by post processors to produce better sounding rips from irrepairably damaged CDs where the CD drives have used the very simple interpolation schemes that produce such obvious audible artifacts.
I think those two additions would keep the 'art' moving forward and, as a side benefit, give us plenty of grist for future robust discussions.
Regards,
Bob