Re: [ARSCLIST] What type of file are music CD's saved as

["Jerry L. Hartke" <jhartke@xxxxxxxxxxxx>]

-----Original Message-----
From: Association for Recorded Sound Discussion List
[mailto:ARSCLIST@xxxxxxx] On Behalf Of Steven C. Barr
Sent: Wednesday, April 21, 2004 10:14 PM
To: ARSCLIST@xxxxxxxxxxxx
Subject: Re: [ARSCLIST] What type of file are music CD's saved as

----- Original Message -----
From: "Don Cox" <doncox@xxxxxxxxxxxxxx>

> On 21/04/04, Watsky, Lance wrote:
> > Does anyone know what type of file a regular music cd is actually
> > saved as?
>
> It's called CDDA and is (at least when ripped to a computer) raw 16 bit
> data with no header.
>
> The high and low bytes may be either way around.
>
> There are subcodes on the disc containing information about the byte
> order and other things, but these are not displayed by normal audio
> software.
>
> WAV and AIFF files are exactly the same but with a header - one of these
> has the low bytes first, the other the high, to suit the CPUs on PCs and
> Macs.
Don't the bits on a CD actually represent some sort of pulse-code
description
of the digital waveform, as opposed to the actual waveform making up the
music? If so, are .WAV files stored in such a way they use the same
algorithms
rather than being a representation of the signal values themselves?
Steven C. Barr

CD-DA (digital audio) discs have a frame structure. Each frame includes 24
bytes of information from an A-to-D converter. Each A-to-D sample occupies
four bytes, or 32 bits, 16 bits of left channel stereo and 16 bits of right
channel. Upon playback, these bits are processed by a D-to-A converter to
recreate the original audio.

Data CD discs have the same frame structure, but the 24 bytes of information
come from a data sector. Each data sector is distributed over 98 sequential
frames. Every data sector contains 2352 bytes consisting of sync, header,
user data, and error correction/detection bytes. These data discs can
contain audio files such as .WAV, or other structures. These are treated the
same as any data file, and the receiving system must process them to
recreate sound.

Jerry
Media Sciences, Inc.