jase wrote:To say "brand X when written at Y speed on brand Z writer caused N C1 errors, this is therefore a bad burn" is actually an erroneous statement. A C1 error count for a certain type of media actually tells us very little about the state of the recorded media on its own, and should not be used as a black and white argument that brand X doesn't work well with writer Z. True?
I wouldn't call it an erroneous statement, but it is incomplete. In general you are right that one measurement alone does not make for a definitive characterization of the compatibility of media brand X with writer Z. But we can still get useful information from such measurements.
I think spath has the right idea here. You need to look at the entire system, including the writer, the medium, the reader and the conditions under which the medium is written and read when considering the meaning of C1/C2 error measurements. All of these affect the measured error counts, but that doesn't mean any one measurement is more or less valid than another. It just means that the conditions under which the measurements were made were different. And since we do want to be able to write and read discs under varying conditions (e.g. high speeds), all of the measurements are of value. But you do need to be aware of the different conditions that underlie the results in order to make meaningful interpretations of the results.
Also, keep in mind that, even though CD Speed, WSES, CD Doctor, etc. are great tools and we are very grateful to have them, they can't characterize a disc at the physical level of detail required to pass judgment on the "absolute" quality of a disc. No tool available to us as general consumers can do this. Thus, we can't specify the absolute quality of media X, and, in fact, it doesn't even make sense to try. At best one can say media X performs at some level under some conditions.
However, this doesn't invalidate the measurement of C1/C2 errors in an effort to characterize media and media/drive combinations. Certainly relative assessments of media quality are fair game. We may find that media X does consistently better than media Y when tested under identical conditions on the same drive. We can then say that media X is superior for those conditions on that drive. And we may find that media X does consistently better than media Y under a number of different sets of testing conditions. Then, we can expand our conclusion to state that media X is generally superior to media Y (keeping mind that there may always be exceptions for specific test conditions).
Having said all that, I would say that measuring a disc at lower read speeds probably does tilt the balance more towards showing errors due to faults in the written disc and away from showing errors due to the reader. The measured errors are still result of the interaction between the two, but lower read speeds likely deemphasize faults in the reader. Still, the best advice probably remains:
ErikDeppe wrote:The results of such tests should be seen as relative comparison data.
(Apologies to those who have read part of this post before. I lifted a portion of this post from an old post that I wrote, because I believe it is germane to this discussion.)