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How much can you _really_ get on a cd?

Your average CD holds 80 minutes of audio data.

CD music has 44100 samples per second.

Every sample is two bytes (16-bit).

There are two channels.

This makes 44100 * 2 * 2 = 176400 bytes per second.

So, for the whole 80 minutes, this is:

176400 * 60 * 80 = 846720000 bytes possible storage space.

Divide by 1024 twice, it makes 807.5MB of storage space.

---

So considering that 80 minute CDs are labelled as "700MB".. imagine I fill a CDR with 700MB of stuff, using the Joliet file system, where has the other 107.5MB of space gone? Surely the lead in/out and file table can't possibly use the WHOLE 107.5MB??

Knowing this, is it possible to 'overburn' as such, i.e. fit a larger amount of stuff onto a CDR?

Thanks people, it was just on my mind...

oke, thank you so much for sharing that with us.

Re: How much can you _really_ get on a cd?

quote:

Originally posted by mr_smidge Your average CD holds 80 minutes of audio data. CD music has 44100 samples per second. Every sample is two bytes (16-bit). There are two channels. This makes 44100 * 2 * 2 = 176400 bytes per second. So, for the whole 80 minutes, this is: 176400 * 60 * 80 = 846720000 bytes possible storage space. Divide by 1024 twice, it makes 807.5MB of storage space. --- So considering that 80 minute CDs are labelled as "700MB".. imagine I fill a CDR with 700MB of stuff, using the Joliet file system, where has the other 107.5MB of space gone? Surely the lead in/out and file table can't possibly use the WHOLE 107.5MB?? Knowing this, is it possible to 'overburn' as such, i.e. fit a larger amount of stuff onto a CDR? Thanks people, it was just on my mind...

so many problems

quote:

Originally posted by Nook oke, thank you so much for sharing that with us.

Well if you've got an itch you've gotta scratch it.

Audio CDs contains up to 30% extra data for error correction purposes.

quote:

Originally posted by trancaholic Audio CDs contains up to 30% extra data for error correction purposes.

Thanks, but this still means that extra storage space is available...

Audio CDs do use error correction, but the error correction used results in about 1 error per hour. This is obviously not good enough for data. So when the data CD format (Mode 1) was developed, an additional layer of error correction was added.

From http://www.mscience.com/faq62.html, "Every 2352 byte Mode 1 sector contains 12 bytes of sync, a four byte header, 2048 bytes of data, and 288 error correction bytes. Read failures for high quality discs are now reduced to about one every 100 years. This is clearly the preferred format for data."

There is another format (XA Mode 2) that reduces the error correction used and should only be used for audio/video files. However, the disks are more fragile to scratches, etc. To complicate things further, there are multiple forms of Mode 2, some of which add synching features but which reduce the usable space on the CD.

Go to http://www.mscience.com/faq62.html for more info on the specifics.

Hope this helps,

Jonathan

school is boring

hey! lets make this a babe thread!

im first:

Jessica Alba









common guys, work your magic!

Thanks Jonathan...

--

Looking at the last few posts though, it all seems to have gone a bit Pete Tong.

quote:

Originally posted by mr_smidge Thanks Jonathan... -- Looking at the last few posts though, it all seems to have gone a bit Pete Tong.

while we're on the topic of cds...

i've downloaded a bunch of movies that are split into 2 parts, cd1 and cd2... but each part is 780MB... how could they have possibly fit on a cd? i have a bunch of 80 min cds, but i'm thinking none of them are big enough... are there cds that can actually fit 780MB?

yes there are...you can possibly fit 780 on a 700 MB CDR and there are special 800 MB CDRs, too. But you need a Drive that supports "overburning" and in Nero you have to enable it before it works, too (it's in the expert section of setup).

quote:

Originally posted by djdawn yes there are...you can possibly fit 780 on a 700 MB CDR and there are special 800 MB CDRs, too. But you need a Drive that supports "overburning" and in Nero you have to enable it before it works, too (it's in the expert section of setup).

according to my knowledge (and experience) theres no way in hell U could put 780mb on a 700mb cdr. Ive done 712mb MAX and thats the limit..

youre right abt the 800mb cdrs, though.. they are out there but theyre expensive compared to 700mb cdrs..

the way audio cd are burnt and normal cds with files are different. Each standard requires different sector size which varies the effective useful data you can hold on a cd...

thats why its 700 megs of effective data file you can hold on a cd.
and about 800 megs of audio on the same cd...

heck they could invent a standard that has 50 megs of data only and take the whole cd....

get the idea?

quote:

Originally posted by djthunderbird according to my knowledge (and experience) theres no way in hell U could put 780mb on a 700mb cdr. Ive done 712mb MAX and thats the limit..

yes there is.

quote:

Mode2 CD Maker - Build Mode2/Form2 CD/XA Bridge images with any file! ===================================================================== Disclaimer ---------- This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. Purpose ------- With this tool you can build a CD/XA Bridge image using any file you want (not just MPEGs). What's the point? Well, using Mode2/Form2 you have bigger user data sector sizes so you can fit more data in a single CD-R (up to 800 MB of data in a 80 min. disc). What's the drawback, then? There is an issue on how Windows handles these discs. It reads the files burned this way as RAW data, and it also appends a RIFF/CDXA header at the beggining of the file. So you cannou burn anything you want ant then just see it like any other file: you must deal with this RIFF/CDXA stuff. Here you have the theoretical max. capacities for each type of media: ---------+--------+--------+--------+--------+ ---------| 74 min | 80 min | 90 min | 99 min | +--------+--------+--------+--------+--------+ | Mode 1 | 650 MB | 703 MB | 791 MB | 870 MB | +--------+--------+--------+--------+--------+ | Mode 2 | 738 MB | 798 MB | 897 MB | 987 MB | +--------+--------+--------+--------+--------+ The Mode 1 line shows the "original" CD capacity, the Mode 2 the one that can be achieved using mode2cdmaker. In the practice you'll have to substract approx. 1 MB from the Mode 2 values since it's reserved for the ISO Bridge track. In my calculations 1 MB = 2^20 (1024*1024), and not this 1000*1000 stupid value used by the HD makers' marketing division.

That's interesting because I've quite often downloaded movies that are ~710-715MB in size but are clearly labelled as CD1, CD2 etc.

How reliable is overburning in Nero? I mean surely that's gotta create incompatibility problems with some readers...

Hmmm, when i was gonna burn 2 movie parts to a 700mb cd nero had to convert the movies to less quality to fit on the disk

The movies were originally like 760mb or something..

well, not all Drives support overburning. Also, different brands of CDRs have different maximum capacity.
There was a great site at come.to/cdspeed but it's down. They had tests on all types of drives and CDRs and the guy who ran the site had a screenshot of succesfully burning a 99 min Audio CD.

But there are problems with playback in certain drives. You just have to test that yourself and see if your player will work...

I don't know if you know about WMA or not but windows media player rips cds in WMA format. they are half the size of mp3s with almost better quality. When I play mp3s then switch to WMA I have to turn the sound down a bit.

Anyway.. A while ago I downloaded this new version of Nero from kazaa and it's got a WMA burning option that's playable with a cd player. So you can practically fit twice as many songs as mp3s on a cd and play it on a cd player.

quote:

Originally posted by Illusion I don't know if you know about WMA or not but windows media player rips cds in WMA format. they are half the size of mp3s with almost better quality.

I wouldn't recommend WMA to anybody. The reason that it's compression sometimes beats mp3 is because M$ have had the cash to plough into R & D for it.. they've come up with something reasonable, but it's Digital Rights Management is a pile of shat that justs wastes our time, and it's not cross-platform as such.. and would be very difficult to get decoders for it.

The only reason WMA is so popular is because computer newbies see that they can rip CDs onto their hdds with Windows Media Player and assume it's the only way to do it..

I would recommend OGG Vorbis if you're serious about how your sound quality is. All we need to do now is to let it catch on (I don't see many WMA or OGG files showing up on DC hub searches...)

i've seen a couple of wma files on the hub but like 1 every 20 searches. i would just stick with mp3 too.

There are now double density CD-R's and CD-RW's available now in case you dont know.

Also remember that some space is taken up by the TOC (Table O Contents) on a CD. Maybe that's where the other 20MB or so is going.

you also have to take into account that this conversation is getting v boaring and needs to be stopped.

Nice Endre!

Dreamer

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