Subchannel Question

vbimport

#1

Lets say I was backing up a game protected by safedisc 2.XX.X

I know safedisc does not use subchannel data in its protections but if I were to enable audio, data subs would it make a difference?

My friend and I were debating, he swears up and down that you get a better copy by enabling them but I was skeptical.

If nothing else, tell me would it make ANY difference in a copy if there was no subchannel protection.

My final question, what is subchannel data and audio? I just know you need it for securom

Any input will be appreciated.

Lite-on 40x
Pioneer 16x DVD
XP Pro
XP 1700
CloneCD 4.0.0.1


#2

Subchannel reading can slow down your overall reading speed, so if you don’t need it, don’t use it!

For more info on subchannels, check these sites:

http://www.chipchapin.com/CDMedia/
http://www.cdrfaq.org/

:smiley:


#3

Enabling SubChannel Data reading for a game that doesn’t use it (like SafeDisc) will not result in a better copy. You cannot copy what’s not present in the first place :wink:


#4

But subchannel data is present on every CD. It’s just a question wether that data is different from standard (emtpy) subchannels. If you, eg., had a SD game that contained audio tracks, these audio tracks might as well contain indices and other information encoded in the subchannel.
The subchannel data from data tracks on SD is, however, almost guaranteed to be empty.


#5

Originally posted by ClayLogic
[B]Lets say I was backing up a game protected by safedisc 2.XX.X

I know safedisc does not use subchannel data in its protections but if I were to enable audio, data subs would it make a difference?
[/b]In CloneCD v4 - no.
My friend and I were debating, he swears up and down that you get a better copy by enabling them but I was skeptical. If nothing else, tell me would it make ANY difference in a copy if there was no subchannel protection.
No. If subs are not read, the hardware just regenerates the subcode channels according to the Colored Book Standard
My final question, what is subchannel data and audio? I just know you need it for securom
SecuROM is data sub only :wink:
Originally posted by drezon
…If you, eg., had a SD game that contained audio tracks, these audio tracks might as well contain indices and other information encoded in the subchannel.
Is this not apples and oranges? Audio CDs have the information you speak of…data CDs, game CDs for example, do not have anything useful in PQ and nothing in R-W.

Upp3rd0G, will, of course, smote me if I’m wrong :stuck_out_tongue:


#6

I was speaking of a hypothetical possibility. I don’t know if there is a (SD protected) game that has audio tracks and, moreover, uses indices to access parts of these audio tracks.
But it is definitely possible that data CDs contain audio tracks (Mixed Mode style), and that these audio tracks contain indices, cd-text, ISRC and similar stuff encoded in the subchannel data.


#7

Originally posted by drezon
I was speaking of a hypothetical possibility. I don’t know if there is a (SD protected) game that has audio tracks and, moreover, uses indices to access parts of these audio tracks.
But it is definitely possible that data CDs contain audio tracks (Mixed Mode style), and that these audio tracks contain indices, cd-text, ISRC and similar stuff encoded in the subchannel data.

Cossacks is a game with data and audio tracks. It is variously protected by ProtectCD (Australia, Asia, parts of Europe), SafeDisc 2 (US, parts of Europe) and Starforce (Russia).

I have the ProtectCD version which does require both subs to be read, due more to the prot than the ensconced audio tracks. Presumably, the SD2 version owners have had no trouble because I’ve only seen one (recently, too).

I think the issue is this, and again may I be smote if I’m wrong, that[ul][li]Audio CDs are Red Book[]Data CDs are Yellow Book[]CD Extra is a two-session CD, 1st is CD-DA, 2nd is data (AKA “CD Plus”) but it’s got no colour book standard[]CD-ROM/XA eXtended Architecture, is a bridge between Yellow Book and CD-i
[/li][li]>>>>>>>>MODE-1 standard Yellow Book sectors[
]>>>>>>>>MODE-2 may be of form-1 or form-2[]>>>>>>>>>>>>>>>>FORM-1 2048 bytes of data, with error correction, for data[]>>>>>>>>>>>>>>>>FORM-2 2324 bytes of data, no ecc, for audio/video[/ul]So what? Well, game discs can’t be CD Extra, because Windows only reads the last session - data, but no audio from the first session. Compact Disc players only read the first session - audio but no data (thankfully). Form 1 and Form 2 can’t coexist so the ‘audio’ tracks on a game CD are written as data.
[/li]
Some newer PC drives can read CD Extra, I don’t have either a disc or such a drive so I can’t comment any further, it would be speculation and spath would rouse on me (again) :wink:

If CDs vary too far from a ‘Standard’ then they run the risk of not being a ‘CD’ and therefore unreadable by a MMC compliant player, like our PC CD-ROM.


#8

and then, philips sues the RIAA for saying they WERE cd’s :wink:


#9

Unfortunately the resulting SUB file seems to be always different, no matter how often or how fast you read the disc.
Otherwise you could make a copy with and without read subchannels and compare the SUBs on the two copies.
Olli said, that Subchannels don’t have any error correction and that’s why they are always different.
To adjust this issue, the SUBs are corrected on WRITING.
But why does a copy still work, even if you DO NOT correct the subs (e.g. PSX Libcrypt) ?

To come back to SafeDisc:

I would be interesting, if the subs are affected when reading bad sectors. In such a case, CloneCD filles up the bad sector. Are the subchannels being filled, too ?


#10

Originally posted by little-endian
[B]…To adjust this issue, the SUBs are corrected on WRITING.
But why does a copy still work, even if you DO NOT correct the subs (e.g. PSX Libcrypt) ?

To come back to SafeDisc:

I would be interesting, if the subs are affected when reading bad sectors. In such a case, CloneCD fills up the bad sector. Are the subchannels being filled, too ? [/B]
<<“But why does a copy still work, even if you DO NOT correct the subs…>>” Because the PSX disc is either unprotected or the writer defaults to DAO-RAW+96[ul][]A DAO-RAW +16 write will correct any errors in the PQ (normally only the Q, which is correct anyway with regard to PC prots)[]A DAO-RAW +96 does not correct anything in the subs and this is all LibCrypt needs to be effective[]LibCrypt has some incorrect CRC, according to Nic & John at CDRInfo, in the Q subcode channel[]A 16+ byte write will correct this; a 96+ byte write will not (MMC)[]Some writers do both 16/96, some do neither (RAW only), some only 16, some only 96[]the 24102b, for eample, does both, but defaults to +16[*]this is why some writers need the “Don’t repair…” checked, to ‘force’ an uncorrected write using +96[/ul]<<“Are the subchannels being filled, too?>>” If subs are not read, they will always be regenerated by the hardware or software during the write (DAO only) to conform to the colored book standards.