SACD - higher risk of errors?

Now that I've finally moved into the incredible world of SACD (after much deliberation I plumped for the SCD-1 and haven't been dissapointed ) I have a question about errors.

As we know, the success of the CD format depends a great deal on error correction. Am I right in thinking that SACD (and all DVD based formats) depend even more heavily on error correction?

Since the pits encoded on the new high density formats are smaller than those on a CD, won't dust, fingerprints, etc cause larger block errors on, say, an SACD? Will an SACD become unplayable much more easily than a CD, or is there a higher level of error correction employed in the new format to compensate for this?

 

I haven't had any problems with SACD's, but I treat them (and dvd-videos) with a lot of care. I think you're correct about the fact that with the higher density of pits the more chance of problems. I have noticed with dvd-video's that a fingerprint can cause playback to stop. And I have had one instance of a dvd rental being unplayable. So the care & handling of high density discs must be more important than CD's.

Also, ironically, Phllips is complaining about these new copy-protected audio CD's. One of the reasons is that after normal wear and tear the CD will become less playable because of these copy protection schemes.

 

I should add that I have only bought 7 SACDs so far - and already I have had one that can't play properly at one point on the disc. On closer inspection of the playing surface I noticed a small number of markings which are in the right place to cause the problem.

With CD I would expect the player to have no problem at all with such a small imperfection.

Steve has mentioned that his 777ES is sensitive to lint on a disc - this is presumably because the lint obscures a much larger number of pits than it would on a CD and so produces a larger block error. Is there not a higher level of error correction employed on an SACD to counter this?

If not it will be more essential to keep the high density discs clean than it was for CD......

 

I think the SACD error correction algorithms are not as comprehensive as the Redbook standard. It has been reported in a number of reviews that they can't correct the diameter of holes that normal CDs can.

There is much anecdotal evidence that they are far more sensitive to lint, fingerprints etc. I have not had any problems with the 61 discs I have (yet). Touch wood.

Whoops - make that 69. The Fed-Ex man just arrived with a package from www.hmv.co.jp - yeah, Santana's "Caravanserai". Too bad I've got to go to work.

Regards,
Metralla

 

Hi Malc,
I've got the el cheapo DVP-NS500V and I haven't had any problems with skipping or faulty discs....
Grant

 

Metralla,

Could you elaborate on "they can't correct the diameter of holes"? What exactly does that mean and how were the "holes" made? Does "correct"-ing mean tracking a disc corectly or making corrections on errors? If the same size of holes are "drilled" diametrically on a SACD and on a CD, they certainly will have different levels of impacts on the two different discs.

It's true that the error correction codes used in SACD/DVD are more sophisticated than in CD. A smaller pit size means higher storage density but can also lead to higher defect/error rates - a defect of the same size affects more pits on a higher density disc. Therefore the big shots would definitely have wanted a more robust ECC system with higher error correcting capability.

However, if an SACD or a DVD player freezes, it is more than likely that its servo system can't track properly, not unsimilar to when a needle keeps skipping back to the same track of a broken record, but for the sound. I know it's annoying but don't kick your thousand dollar SACD player like you do a jukebox (which can be more expensive today ). Just hit the "Fast Forward" (>>) button. If the player stops playing completely, it could be some kind of fail safe mechanism which has nothing to do with error correction.

The ECC circuits in the controller IC will find a "frame" of data to be either errorless or erroneous. The errors could be:
(a) Detectable & correctable: You are so lucky that all the corrupted bits are recovred.
(b) Detectable & uncorrectable: You are so unlucky that the ECC can't correct all the errors.
(c) Undetectable: Theoretically probable but practically impossible. There are so many errors in the frame and you are so darn (un)lucky that the ECC "thinks" the corrupted frame is errorless. This is like swapping one errorless frame with another.
Whichever category the error pattern falls into, there should be a GIGO (garbage in, garbage out) mode to handle it for non-data critical applications aka audio and video.

No types of error patterns should make the player stop or freeze. Most people designate the ECC as the scapegoat. Having studied a thing or two on coding, I always find it easier to blame the servo and the front end of an optical transport. Can't do heck if you can't track the darn disc.