How to cut an audio CD at the IfA
And a handy CD FAQ
This document will explain how to cut an audio cd with PPC2 and the Hammer CD-cutter in the graphics lab. The actual instructions are followed by some notes
on the way CD's are formatted.
First, RTFM! In particular, read the Toast manual - it has a lot of valuable info in it.
Next, you need some audio data, 1 sample file per song. This data must be in the following format:
This data can be extracted directly off an audio CD. You cannot just copy the files. This will only produce garbage (see notes below).
You must do the following:
- AIFF format
- 16 bit
- 44.1 khz
You are now ready to cut the CD.
- Insert your audio CD in PPC2's internal drive.
- Get the program CDtoAIFF
- Choose "Multi-Record"
- Select all the audio tracks for extraction. Be sure to save the data to the CD staging disk. You will need about 700 meg free.
- This will save each audio track to the staging disk in the correct format.
Don't worry about the names. CDtoAIFF will give them sequential numbered names, which will make the mastering step easier.
- Go have a snack. It will take 30-40 minutes to extract all the audio data.
- Open the control panel "extensions manager".
- Select the "Toast" extension set. Everything runs better with less background crap running.
- Turn on the Hammer CD-cutter.
- Restart the machine.
- Star the program "CD Toast"
- Choose "Audio CD" from the Format menu.
- Drag your audio files into the box, or add them with the Add button.
- Select Simulation Mode. If the cutter fails, it will ruin your CD-R.The simulation mode actually carries out all the commands, but doesn't tell the laser to turn on.
- Click Ok to cut. Don't worry about the speed test - PPC2 is
very fast, and the cutter is very slow, so there is no real likelihood
of the cutter outrunning the data stream.
- Insert a blank CD-R. Be sure to clean all the dust off.
- Click on Write Disc. You could also do Write session, but
CD-players can only read the first session.
- If it works for 30 seconds or so, hit option-. a few times to stop the test.
- Turn simulation mode off, and repeat the above.
- It will take 30 minutes to cut the disk.
This is a source of considerable confusion, but you must understand it if you are to be successful in mastering anything more than the most basic CD's.
The CD was created as a means of storing audio data. Storing computer filesystems on them came later, when it was realized how cheap and versatile a media it was.
Eventually, the CD would be used as a storage medium for many
different applications. This add-on nature to the physical medium has resulted in a pretty complex formatting scheme. This is also why CD's are measured in units of (audio) time, and not kilobytes. There are additional complications, like the fact that a writing laser cannot turn off instantly, so there needs to be dead time allowed in the CD, etc.
In order to standardize things, there are several major recognized formatting
schemes, commonly referred to as "books".
However, the basics are:
And here are the formats you may encounter:
- A CD contains one or more "sessions". Each session refers to a single,
continuous writing event. Most CD's have only one session. A few (like Kodak
Photo-CD's) have several. You should generally only write one session to a
disk, since most implementations do not recognize multiple sessions
- Each session contains one or more "tracks". In an audio disk, each track is a
song. In a computer data disk (CD-ROM), each track is generally a filesystem.
- Each track consists of "sectors". These sectors are the actual, byte-level
data streams. There are 5 types of sectors, each for storing different
kinds of data. Each track consists of only one kind of sector.
- Type 1 - Audio (Red Book) - used for audio CD's
- Type 2 - Data (Yellow Book) Mode 1 - computer data
- Type 3 - Data (Yellow Book) Mode 2 - almost never used
- Type 4 - CD-ROM XA (Green Book) Mode 2 Form 1 - computer data
- Type 5 - CD-ROM XA, vCD (Green & White Book) Mode 2 Form 2 - compressed video and audio
Confusing? You bet! What is worse, it is possible to mix the different formats,
and some manufacturers do for special applications.
- Red Book - also known as CD-DA. This is the format for recording audio
CD's. One session, with a track for each audio stream (song).
- White Book - also known as video CD. This stores the data as MPEG streams, and is readable in video CD players and CD-i machines. Pretty uncommon, except in Japan.
- Orange Book - this simply refers to the standards for a blank CD-R. Any CD-R is Orange Book, as well as some other book.
- Yellow Book - the standard for CD-ROMs. This only specifies how the data is stored physically on disk, not the logical disk structure. So, for example, a CD-ROM contains a track which is an image of a disk structure, which is
essentially a giant file. See the examples.
- Green Book - the CD-i format. Used by CD-i players (an interactive set-top box).
- Blue Book - the CD-enhanced standard, which has replaced CD+. This consists of 1 session of audio tracks, followed by another session of data track(s). This way the disk can be played in an audio CD-player, or put into a computer for additional functionality.
- CD-ROM/XA - special track type consisting of mode 2 sectors mixed with other formats to create mixed-mode CD's.
- Mixed-mode - format consisting of multiple audio and data tracks in
a single session.
- Multisession - just what the name says. Found mostly in Photo-CDs.
Example: An audio disk
This disk consists of one session, with any number of tracks. Each track consists of Type 1 (Red Book CD-DA) sectors. These tracks are what a CD-player shows
as Song 1,2,3, etc.
Example: An ISO9660 computer disk
This disk contains one session, whose name is the name of the disk. This session contains one track, called "ISO 9660". This track consists of Type 2 sectors. Encoded into the track is an ISO9660 disk image. This is why the CD-cutters have to go through a mastering phase when cutting data CD's, since the actual
data is stored as an enormous file whose internal structure conforms to
the disk standard.
Example: A "hybrid" Mac/PC disk
This disk contains one session. The session contains two tracks. The first track is an ISO9660 disk image, while the second is an HFS disk image.
Example: A Sony Playstation Disc (mixed-mode CD-ROM XA)
This disk contains one session, whose name is that of the disk. The first track
is an ISO9660 disk image containing the game data. The subsequent tracks are
CD's in devices they aren't supposed to be in:
Strange and unexpected things happen when placing a CD into a device it
wasn't specifically designed for.
This is mostly due to the plethora of different data formats and sector types.
Most CD implementations try to "guess" what to do with a disk. Sometimes
it isn't exactly right, or it may be misleading. A classic example is putting an audio CD in a CD-ROM drive. A computer cannot directly read the audio data because it is the wrong sector type,
although special software can read the audio sectors (actually, many older drives can't read them at all).
However, the computer will read the disk Table of Contents, and happily display the files as if they were real (this is why you can see the audio tracks on a Mac, but can't do anything with them).
If you place a CD-ROM in an audio player, it will interpret the 650 meg data
track as a very long song. Do not try this! The data, translated into audio, will
make a lot of speaker-destroying snapping and popping.
If you put in a mixed-mode CD, it will play the audio tracks, but may or may not see the data tracks.
Why the cutting speed matters:
Sessions must be written continuously, without turning off the laser. This means that the cutter must never run out of data to write to the disk.
Therefore, the computer supplying the cutter with data must be fast enough to keep up with it.
This is not a problem for us, because we only have a double-speed (300 kb/sec)
recorder and PPC2 is very fast.