Mode1/Mode2 CDRs

[ToMmY]

I read Doom9's article about 800 mb cds...
and there is something i want to ask...

Up till now i didnt know the difference between mode1 VS Mode2
I use Nero and it lets you use both modes for creating a data cd.
So i thought (up till now) that there is no real difference and i have been using mode2 for my backups, mp3 cds, and divx cds.!!

Will i have a problem in the future about error correction??
Will my data cds fail to work or my files get corrupted??

Please answer with as much detail as you can.

Thankz

[avih]

you're safe, don't worry ;)

i nearly had a heart attack myself when i realized mode 2 might not be safe, since i was using mode 2 as well with nero. so i immidiately checked that out, and found out that:


first, for extensive information about different CD modes, go to dext's page ( http://www.wsu.edu/~benp/mcfcd.htm ).

there are 3 basic modes a file can be stored on a CD:

1. "mode 1" file. in this mode there's error correction (about 13% of each sector), so each sector is 'protected' to some extent. that's the normal method for putting data files on CD (which most burner applications use as default).

mode 2 file: this mode has 2 forms:

2. "mode 2 form 1" is quite similar to mode 1, (except for small header differences), it can be read by the OS without problems, and uses error correction codes the same way mode 1 does. that's the mode your files are burned when you select mode 2 from your burnning application.

3. "mode 2 form 2" is without error correction, and uses as much as possible area of the CD for actual data (the rest is used for neccessary sector sync section, header, subheader and error DETECTION)

all in all: mode 2 form 2 allows using 2324 bytes of each sector for actual data and 28 bytes of each sectors are used for the cd struture mentioned above. while mode 1 file uses more or less as mode2form2 PLUS 276 bytes for error correction (thus allowing 2048 bytes of data).

your burnning program will probably burn mode 2 form 1, since it 'knows' that form 2 file may be unreadable after some time.

VCD and SVCD CDs use mode 2 form 2 since mpeg streams already have embedded error ressiliance. XCD will (and the mode 2 filter is) using mode 2 form 2 files.

hope you feel better ;)
avi

[jonny]

Hi :)

I want to tell a little word about this.

In the past i was tring to find an answer to this question: why we can't use the FULL capacity of the cd?

Now someone is came out with a REAL implementation of this.

I'm happy to see how the things are evolving :)

[ToMmY]

Thankz avih

You are great:D

I nearly had my self a heart attack too...
...but you saved my life....
...and my 200 cds :D

I only hope Nero (v5.551) DID use "Mode2 form1" :confused:
It calls it "Mode2/XA"

Thanz again

[DeXT]

Yeah Mode2/XA (or simply Mode2) is ALWAYS Mode2 Form1 for data. Form2 is only used with S/VCDs for MPEG content.

If any single CD recording tool out there would have been able to create Form2 with data files I never would have done my tool, and my life would be much easier, too ;)

BTW my home page is webs.ono.com/de_xt, the previous one is ReferenceDivX's.

Bye!