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Originally posted by Halcyon
This is an interesting discussion.
1) Their results are relative and can only be compared to other drives they've tested with the exact same methodology (it has changed once or twice during the time they have run the DAE quality / C2 error tests)
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Unfortunately so. The Abex discs probably produce consitent results from test disc to test disc otherwise they wouldn't be much good. The EAC test discs will depend on who made them so you would have to use the exact same one to get directly comparable results. Nevertheless, as long as the EAC discs are not too far apart, the test results should be indicative of performance. I would like CDR-info to run the current tests on some older drives so that we can get direct comparisons between generations of drive. I would be especially interested in testing the whole range of Liteons (due to their populartiy) and the Plextors. But I will not be holding my breath.
Quote:
Originally posted by Halcyon
2) Pressed C2 errors are only data level errros. Most real life C2 errors are physical level errors. To read these properly the transport, pick up and servo also matter a lot. Even reading the same spot twice might produce unreadable and readable results on the two occasions (this is what EAC uses too).
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Actually, from what I have seen, most of the Abex tests are for physical defects. I was more interested in using specific error patterns to test the performance of the error correction and c2 reporting completely isolated from servo/laser/EFM/Synch performance. It should be possible with sufficient tests to determine quite a bit about the strategy and performance of the particular CIRC implementation, its interpolator performance and subsequent C2 reporting. The advantage of using artificial errors is that the results are repeatable and you can have a genuine comparison.
Actually all errors are physical errors. The difference is how those physical defects are formed. There are random errors which can only be one symbol (byte) maximum length or one malformed pit (one of the interleaves seperates the possible two symbol burst that some malformed pits would create). These errors can only occur at the mastering/burning level and because of their size cannot be generated by 'damaging the disc'. The other errors are burst errors as generated by scratches, dust, etc. However it is often useful to look at burst errors as short or long bursts as different CIRCs have variable performance for each case. Most discs contain a combination of both with the random error rates having a considerable impact on CIRC burst error performance.
Quote:
Originally posted by Halcyon
3) Could we have a STANDARD physical layer error disc (not just data layer) that had scratches of several levels of severity. This would not only test the C2 ability, but also the pickup/servo/transport performance. As such it would be a much better approximation of real life performance with scratched discs.
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The Abex and Philips test discs already do this with spots,bars,etc. The trouble is that using large defects to test CIRC and C2 can only give you results for high error rates. In my opinion these error rates are so extreme that they are almost irrelevant for most EAC users. None of these technigues will test a drive for low error rates as is common on most CDs. Just how inaccurate at low error rates are those drives that rate poorly at extreme error rates? Are the Plextors as bad as some tests would indicate or do they just have problems with severely damaged CDs?
Quote:
Originally posted by Halcyon
PS In a way I hope that we are discussing the remnants of a dying standard which will hopefully be supplanted by SACD/DVD-A or something else... Redbook implementation has way too much black magic associated with it to be a contender for a reliable standard in audio delivery in the 21th century, imho.
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There is no 'black magic' in red book. Unfortunately Philips/Sony missed a couple of details that makes audio ripping 'interesting'. Certainly SACD/DVD-A have enormous advantages over red book in booth decoding accuracy and digital audio performance. However both of them are based on DVD disc standards which are more expensive to produce (especially the hybrid discs).
Also there is the issue about the source material, much of it is very poor and most old analog master tapes continue to deteriorate, whereas many early digital transcripts had problems especially with 48ksample recorders which then had to be resampled for CD.
In was my hope that DVD would not have caught on as well as it has as I believe it did not offer enough advantages to be be the replacement for CD, perhaps Blueray ML with its enormous storage density will be a better replacement. Philips have been pushing their 30mm 1gig+ disc and it does have charm but are those cover notes going to be hard to read!
Regards,
Bob