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Topic: Another Question Concerning Cache In Eac Settings (Read 4147 times) previous topic - next topic
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Another Question Concerning Cache In Eac Settings

Hello,
So i have read as much about EAC settings and done a search on the official EAC forum as well as on hydrogenaudio, and wanted one final clarification.

It seems like the general idea is that if your drive caches audio data, and you do not disable the cache in the EAC settings, then EAC will never report an error (since it is re-reading from the cache instead of the disk).

Well, with my Lite-on 48/24/48/16 CD-RW/DVD, I have burned several CD's without disabling the cache.  EAC still detects read and sync errors with certain disks.  Everything goes faster and when it has an error, it doesn't spend as much time as it normally would (if cache was disabled).

Also, sometimes when I do disable the cache, and it discovers read/sync errors, i often try to re-rip it without disabling the cache, just to see if the drive would still detect the errors.  It still does, but everything goes faster.

So my question is... if your drive DOES cache audio data, and you neglect to check the checkbox, does that mean that EAC will NEVER detect read/sync errors?  And with the same logic, if i do get read/sync errors without disabling the cache, can i safely assume that my drive can continue to provide secure rips without disabling the cache?

I guess my source of confusion is that my drive supposedly caches audio data, but EAC still detects errors when i select the option.  It makes me wonder if i can continue to rip at the higher speed without disabling cache since EAC seems to correctly detect errors in that mode. 

Thanks for any advice and clarification you can provide!

Another Question Concerning Cache In Eac Settings

Reply #1 –
Your drive audio cache might be smaller than EAC's read buffer size. So when it rereads, only a part of the audio comes from the cache, and the rest from the CD, where errors are detected.
In this case, some errors can be overlooked.

Another Question Concerning Cache In Eac Settings

Reply #2 –
Quote
Your drive audio cache might be smaller than EAC's read buffer size. So when it rereads, only a part of the audio comes from the cache, and the rest from the CD, where errors are detected.
In this case, some errors can be overlooked.
[a href="index.php?act=findpost&pid=270700"][{POST_SNAPBACK}][/a]


interesting.. thanks for the response.  i guess i will stick with the cache off just to be safe.  is this a common thing (cache being smaller and thus still being able to detect errors?)

Another Question Concerning Cache In Eac Settings

Reply #3 –
DubleoSyx' PDF guide says "Also on drives that don't reportedly cache you may as well check it anyway to be safe, since it won't affect anything."

On one of my drives if i leave it checked, then it will screw up trying to rip by immediately starting error correcting and never getting anywhere.

Another Question Concerning Cache In Eac Settings

Reply #4 –
My understanding from the guides is that if your drive caches audio, then you select the box (default).  That way when an error is detected the cache will be flushed (because you have told EAC that the drive does cache) and the disc will be read again, following the methodology of EAC.  If your drive caches audio and you do not check the box, when a discrepency is discovered it will read from the cache first and most likely read the same info biasing the discrepency check thus defeating the purpose of EAC's ability to reread the data from the disc when it finds an error.  So the speed you gain is at the loss of true secure extraction.

Another Question Concerning Cache In Eac Settings

Reply #5 –
Thanks for the tip.  i didn't know that until now.  I've been ripping all this time with the cache on, since it's what eac detected on my drive.   
WavPack 4.31 / LAME 3.98 alpha 3 -V9 -vbr-new

Another Question Concerning Cache In Eac Settings

Reply #6 –
Had a look at the EAC website.

This says that the cache feature should be turned on:

Quote
Automatic Feature Detection Technology

From version 0.8 beta on it is possible to autodetect CD-ROM drive features. For each drive the program builds a separate drive options page. On this option page this function can be called.
There are two different features that will be checked by EAC: First if the stream is accurate and second, if the drive caches audio(!) data. Even if the drive has a cache (drive specifications), it does not automatically mean that the drive uses the cache for audio extractions.
The test for the accurate stream feature should be always correct, but testing for cache will give some problems with drives that extract audio very slowly (under 4X speed). If results are uncertain (given e.g. two different results on different tests), you should assume that the drive does caching. The new secure mode for non-accurate and/or caching drives should work for all drives. The other new read modes are only a bit faster. If testing for accurate stream only sometimes gives a negative result, then you could nevertheless try to use the accurate secure mode.
WavPack 4.31 / LAME 3.98 alpha 3 -V9 -vbr-new

Another Question Concerning Cache In Eac Settings

Reply #7 –
Quote
"This says that the cache feature should be turned on"

Yes, the ''Drive caches audio data'' option should be checked (selected) - so EAC will not read data stored in the drive's cache.  In an EAC extraction log, (for a secure mode rip) it should show "Secure with NO C2, accurate stream, disable cache".

A couple more sources with explanations of why drive cache should be "disabled":

Quote
The Coaster Factory

EAC reads every audio sector twice and compares them. If the two sectors are different EAC knows that a read error occurred and will reread the suspicious sector over and over again until a satisfying result is achieved (or an error reported to the user). If a drive caches audio data EAC will read the audio data from the cache on the second read attempt instead of from the CD. Of course the buffer always gives the same sector to EAC so the error detection no longer works. If the first sector is read incorrect EAC will not detect this as the buffer will give EAC the faulty audio sector twice. Since no difference between the two sectors is detected EAC will assume that the sector is read correct what is obviously not true. In this case the "Drive caches audio data" option has to be enabled, so that EAC will clear the cache by overreading it.

Quote
Essential Ripping Guide

All drives cache but not all cache audio. "Yes" informs EAC that your drive caches (= remembers) the audio it reads. As you know, EAC needs 2 reads to find errors - but an audiocaching drive will not read a second time but instead send the cached first read again to EAC. Like that EAC can never find any errors! I will call these slip-through-the-net errors: errors in your rip that EAC and you don't know about. Solution: for such a drive, set audio caching to "yes", which informs EAC it should empty the cache every time - yes that costs speed.

Another Question Concerning Cache In Eac Settings

Reply #8 –
Quote
My understanding from the guides is that if your drive caches audio, then you select the box (default).  That way when an error is detected the cache will be flushed (because you have told EAC that the drive does cache) and the disc will be read again, following the methodology of EAC. [a href="index.php?act=findpost&pid=270798"][{POST_SNAPBACK}][/a]


That's the case if you check C2. Otherwise, the errors might not even be detected, since EAC reads twice to detect errors.

Another Question Concerning Cache In Eac Settings

Reply #9 –
thank you for all of the replies.  i'll stick with cache disabled, to be on the safe side.  i notice that instead of "read errors" (that i get when cache is disabled), i get more "sync errors" (when i do NOT disable cache).  either way, i do in fact get errors detected even when the cache is not disabled, so it is tempting to just leave it on (unchecked) and rip faster.  oh well

Another Question Concerning Cache In Eac Settings

Reply #10 –
It is probable that your drive caches, but since you seem to want to question it , you might want to have a look at this thread where Pio2001 lists the main methods to detect caching. These will give you a reliable answer, although in practice you might need to try a lot of CDs before you get there.