CD-R Question

[ArthurR]

Some time ago I bought some Intenso CD-R's, packet of 10, I use them for recording disc's for use in the car. On the packet it say's 800MB, Today I tried to record 738MB, and was told "not enough room, required space 738MB, Available space 701MB" , so I tried another, same message, a third one, same message, I have no receipt from where I bought them, but is not advertising something as one thing then finding something else illegal. Anybody any ideas how I can proceed?

I had used 3 previously but under 700MB

[bit-twiddler]

It comes down to the formatting of the data on the disc.

Much like a hard drive there are overheads for things like error correction and the file tables. Using the audio frames format calculation (with 75 frames of data per second)

74 minutes CD = 74 min. * 60 sec. * 75 = 333000 blocks
80 minutes CD = 80 min. * 60 sec. * 75 = 360000 blocks.

With the regular "Data Mode 1":
74 min CD = 333000 blocks * 2048 bytes = 681984000 bytes = 650.4 MB
80 min CD = 360000 blocks * 2048 bytes = 737280000 bytes = 703.1 MB

Now with the "Data Mode 2" have:
74 min CD = 333000 blocks * 2336 bytes = 777888000 bytes = 741.9 MB
80 min CD = 360000 blocks * 2336 bytes = 840960000 bytes = 802.0 MB

With "CD-ROM-XA Mode 2 Form 2":
74 min CD = 333000 blocks * 2324 bytes = 773892000 bytes = 738.0 MB
80 min CD = 360000 blocks * 2324 bytes = 836640000 bytes = 797.9 MB

The error correction is important for computer data, less so for the video stream data that would normally use mode 2 or XA.

So you could write more to the disc by changing the format you write, but you would lose reliability of the data. The discs could store 800 Mb - just it's not advisable if you actually want to access the data again.

[A2QFI]

Take them back to where you bought them and see what they say. You could try Trading Standards but I don't think they will be interested in chasing a bit of under capacity on a pack of discs that didn't cost £10

[ArthurR]

Bit-twiddler, the recording was attempted on Nero 9. the message came before the burn..
A2QFI, I do intend to try that in the morning, I agree with what you say, yes they where under 10€, but does that not still count as fraud?

[frostbite]

All media, be it HD, CD, DVD, SD etc., is advertised in unformatted capacity, because it looks better. (Just as most prices end in .99)

The shop will think you're trying it on, and I would tend to agree.

[bit-twiddler]

As mentioned above it is not fraud as you could put 800 Meg of data on there if you wanted. Just that you would have no error checking and no other applications would be able to read them.

Nero defaults to mode 1 when it is burning a data CD as it assumes, usually rightly, that you want to make sure the data is correctly written. I believe you can set to mode 2 if you want but then there is no guarantee that the car CD player would read it.

Think you missed the point about the amount of data stored on the disk though - Nero still writes 800 Meg to a CD in mode 1 but it consists of something like:
2048 bytes of user data + 288 bytes of error correction

the 288 bytes are transparently inserted and removed from the data stream as you use the disc.

On top of that you lose some of the sectors due to the format that is laid on top of the data - you need to know the names of the files and where they are stored etc.

Before Nero starts writing the disk it checks and knows what size data it can write in each of the modes.

[mixture]

Arthur,

Go to this website, read the paragraph entitled "How much information can actually be stored on CD-R and CD-RW discs?".

Understanding CD-R & CD-RW - Disc Size and Capacity (http://www.osta.org/technology/cdqa7.htm)

[ArthurR]

bit-twiddler: thanks for the information, it explains a lot, still think they should print on the packages the amount of actual space available for recording ect though, to help numpties like me...

mixture: thanks for the link again it explains a lot.