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Topic: Unreliable drive. Ok to force accurate stream and (Read 6701 times) previous topic - next topic
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Unreliable drive. Ok to force accurate stream and

I am not quite confident about the Accurate Stream and C2 information that my drive returns.  Its a LTR-48246S.

In EAC, to be on the safe (and secure) side, is it ok to keep Accurate Stream and C2 always unchecked ? and also always enable/check "Drive Caches Audio Data" ? I understand this will result in a substantial reduction in speed but I am fine with that.

Unreliable drive. Ok to force accurate stream and

Reply #1 –
I think accurate stream can safely be checked. The last time I saw a device that didn't support that feature was when I was using my Mitstumi CR-4802TE, which was over five years ago.

Oh, and since the LTR-48246S is very similar to my old LTR-52246S, I am 99.9% sure that accurate stream is supported.

Unreliable drive. Ok to force accurate stream and

Reply #2 –
In your case I'd rip with burst Test & Copy, and when CRCs don't match I would use secure mode with your settings (Accurate... checked, Caches... checked, C2... unchecked).

Unreliable drive. Ok to force accurate stream and

Reply #3 –
I am really not comfortable checking/enabling Accurate Stream. Nero CD speed detects accurate stream erratically. So my current settings are -

Accu - Unchecked
Cache - checked
C2 - unchecked

Can someone explain what exactly EAC does behind the scenes when the Accurate Stream is checked v/s unchecked ?

<edit:>
btw I just flashed the firmware up to SS0E (from SS04).

Unreliable drive. Ok to force accurate stream and

Reply #4 –
EAC reads 27 sectors per read command in bursts of 2MB. If "Accurate Stream" is enabled, then each 2MB block is synched together(read-overlap) with the next 2MB block, with 2 sync sectors. If "Accurate Stream" is disabled, then each 27 sectors block is synched together with the next 27 sectors block, with 2 sync sectors, and this continues throughout the hole 2MB block.

Unreliable drive. Ok to force accurate stream and

Reply #5 –
Your Lite-on definitely supports Accurate Stream.  I think you'd find that everyone on HA that has liteon uses accurate stream.  It's the recommended setting.
"You can fight without ever winning, but never win without a fight."  Neil Peart  'Resist'

Unreliable drive. Ok to force accurate stream and

Reply #6 –
Quote
EAC reads 27 sectors per read command in bursts of 2MB. If "Accurate Stream" is enabled, then each 2MB block is synched together(read-overlap) with the next 2MB block, with 2 sync sectors. If "Accurate Stream" is disabled, then each 27 sectors block is synched together with the next 27 sectors block, with 2 sync sectors, and this continues throughout the hole 2MB block.
[a href="index.php?act=findpost&pid=367938"][{POST_SNAPBACK}][/a]


Just to make sure I understood this -

By 'sync' do you mean it does a sanity-check/validates the EFM (8-14) to see if it got the bits right ?

If that's correct then it means with Accurate Stream on it will do this periodic "check up" in chunks of 27 sectors at a time, but if it is off then it will do this check for every sector.

So is it safe to say that EAC does not totally rely on the drive's accurate stream feature ? and does it really matter if it syncs all 27 sectors at a time or each of the 27 sectors, as long as it does the syncing ?

Unreliable drive. Ok to force accurate stream and

Reply #7 –
EAC reads 27 sectors per read command in bursts of 2MB. When "Accurate Stream" is enabled, then each 2MB block read are synched against the next 2MB block read with 2 sectors read-overlap(2 sync sectors). When "Accurate Stream" is disabled, then every read commands 27 sectors read, is synched together with the next read commands 27 sectors read, with 2 sectors read-overlap(2 sync sectors). So if "Accurate Stream" is disabled, then EAC only uses 25 out of 27 sectors per read command for data and then 2 sectors as sync sectors for the read-overlap against the next read commands 27 sectors read, but when "Accurate Stream" is enabled, then it's only 2 sectors out of the whole 2MB blocks that's used for sync sectors(read-overlap). It's because if the drive hasen't the "Accurate Stream" feature, then it dosen't have a fixed read offset and hence, every time EAC sends a read command to the drive, then EAC needs to check that the drive is actually reading at the correct place, and that is done by checking for the 2 sectors read-overlap between every read commands 27 sectors read. When EAC reports a "Read Error", then there have occured a read error in the read data, but the drive hasen't skipped, and when EAC reports a "Sync Error", then there have occured a read error in the read-overlap area(sync sectors) and hence, EAC knows that the drive has skipped, since the sync sectors areren't matching up as they should if the read had occured at the correct place...

Unreliable drive. Ok to force accurate stream and

Reply #8 –
Thank you!

Quote
EAC reads 27 sectors per read command in bursts of 2MB.

just out of curiosity - would that be equal to ~33 read commands of ~63Kbytes each ? (assuming sector size of 2352 bytes)

if thats correct then basically the gist of your explanation is that if accu stream is enabled then eac verifies the read-overlap every 33(or whatever) read commands, v/s each and every read command if its disabled.

Unreliable drive. Ok to force accurate stream and

Reply #9 –
Along with the other suggestions make sure DMA is enabled for your drive!

Unreliable drive. Ok to force accurate stream and

Reply #10 –
Quote
EAC reads 27 sectors per read command in bursts of 2MB.
Did you test it by yourself or is it what Andre said ? Because this is not
what EAC does on any of the 5 drives I have.

Unreliable drive. Ok to force accurate stream and

Reply #11 –
Hi spath

No, i haven't tested it myself, and if i have said something wrong then i apologise. I once asked Andre on his forum about different technical questions about the inner workings of EAC, and my previous post was purely based on my understanding of Andre's answers, but maybe i have misunderstood something(btw, Andre also said that i should keep in mind that his answers was only from memory and that he wasen't 100% sure everything was correct). Also i forgot to say that when "Accurate Stream" isn't enabled, then EAC also always enables "Drive caches audio" and so EAC first reads 27 sectors, then overreads the cache and then the next 27 sectors is read which then is synched on two sectors and this continues until a burst of 2MB is read.

Here is the link to the thread :
http://www.digital-inn.de/showthread.php?p=102645

Unreliable drive. Ok to force accurate stream and

Reply #12 –
Hi Martin,

I think you understood correctly what was said in the thread you linked, but
what I see here is that in secure mode with only Accurate Stream enabled
EAC reads 25 sectors at a time in bursts of 41 reads with an overlap of
500 sectors. Funny that Andre cannot tell for sure how his program works

Unreliable drive. Ok to force accurate stream and

Reply #13 –
Thank you for the correct information, spath

CU, Martin.

Unreliable drive. Ok to force accurate stream and

Reply #14 –
The tool tip for "Fast Mode" (under Synchronized Modes) says that you should use fast mode if your drive does not support Accurate stream.

Then whats the difference between UNchecking "Drive has Accurate Stream" and using "Fast Mode".

Unreliable drive. Ok to force accurate stream and

Reply #15 –
EAC has two unsecure reading modes, one for drives with Accurate Stream called burst mode and one for drives without Accurate Stream called Fast mode, which simply is burst mode with added sector synchronization. The EAC Extraction Technology page describes Fast mode as using 2 blocks of 23 as sync blocks.
Quote
Then whats the difference between UNchecking "Drive has Accurate Stream" and using "Fast Mode".

Besides using sector synchronization, then Secure mode reads twice or checks for C2/CU flags returned from the drive + additionally rereads on detected errors, while Fast mode only uses sector syncronization and nothing else.

Unreliable drive. Ok to force accurate stream and

Reply #16 –
An LTR-48246S without accurate stream is a broken drive.

Unreliable drive. Ok to force accurate stream and

Reply #17 –
Martin, thanks for explaining.
so if a drive corrects C2 errors reliably, and also has accurate stream, then burst mode should be good enough, right ?
I know the problem is finding a drive that will correct c2 errors properly 100% of the time.
Does this drive "report" c2 errors or "correct" c2 errors when found ? If not are there drives that actually correct the c2 errors ?

Unreliable drive. Ok to force accurate stream and

Reply #19 –
Quote
You are mixing up reporting and correcting of errors.
[a href="index.php?act=findpost&pid=374342"][{POST_SNAPBACK}][/a]

In other words: EAC is only concerned with uncorrectable errors anyway. Correctable errors are corrected by the drive itself before sending the data to EAC, so EAC never knows (or cares) about these "corrected errors". Only if the drive reports "I have found an error in sector xyz", EAC tries to re-read this sector to get an error-free reading. So the problem is that some drives may not report that they have encountered an error when in fact they have, thus making EAC believe that everything is fine when in fact it isn't. However, I guess most modern CD-RW/DVD-RW drives should be reliable in reporting uncorrectable errors, but I think I haven't seen any controlled tests that prove this. Does anybody know one?
Proverb for Paranoids: "If they can get you asking the wrong questions, they don't have to worry about answers."
-T. Pynchon (Gravity's Rainbow)

Unreliable drive. Ok to force accurate stream and

Reply #20 –
so its really the CU errors (or uncorrectable C2 errors) that we are talking about, and these are what eac tries to correct by slowing down and reading over and over again.
The drive would have already corrected the correctable c2 errors and only passes on those that it cannot correct.
 

Unreliable drive. Ok to force accurate stream and

Reply #21 –
Correct.