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

[Michael Fingerhut <mf@xxxxxxxx>]

Don Cox wrote:

> The numbers in an ordinary 16-bit 44.1KHz WAV file are exactly the same
> as those on an audio CD. The difference is that a WAV file might have a
> different number of bits, or sampling frequency, so it needs a header to
> say what these are, and how many channels are present.
>
> Most WAV and AIFF files are 2-channel 16-bit 44.1KHz, in my experience.

WAV is a much more complex file format than just PCM and thus may greatly
differ from the data on an audio CD, not only on account of the header and
channel numbers. Here is how:
- WAV files are composed of one or more "chunks" of audio data (as well as
other types of chunk, see below), each of which may be mono, stereo or have
any number of audio channels.
- The audio may be uncompressed or compressed, and even include data to be
played by a synthesizer (using the "sampler chunk"), specifying such
parameters as pitch modification, loops, and so on.
- It may contain so-called "cue chunks", which are markers into the (audio)
data, and which can determine a different playing order (using the "playlist
chunk"). Those markers can be labelled (using the "associated data list").

The WAV format is itself a subset of RIFF (looks awfully like "AIFF" this
word does, right; it means "Resource Interchange File Format"), a file
format for storing many kinds of data, primarily multimedia data like audio
and video.

A couple of useful references:
- http://www.borg.com/~jglatt/tech/wave.htm
- http://www.lightlink.com/tjweber/StripWav/WAVE.html

The official Microsoft definition of RIFF is here (beware of folding URLs):
http://msdn.microsoft.com/library/en-us/multimed/htm/_win32_resource_interchange_file_format_services.asp

Michael Fingerhut
Director, Multimedia Library
and Engineering Bureau
IRCAM - Centre Pompidou
Paris, France