Digital Sound & Music: Concepts, Applications, & Science, Chapter 5, last updated 6/25/2013
In order to keep up efficiently with the constant stream of data, the hard drive needs a
dedicated space in which to write the audio data. Most audio recording programs automatically
claim a large portion of hard drive space when you start recording. The size of this hard drive
allocation is usually controllable in the preferences of your audio software. For example, if your
software is configured to allocate 500 MB of hard drive space for each audio stream, 500 MB is
immediately claimed on the hard drive when you start recording, and no other software may
write to that space. If your recording uses 100 MB, the operating system returns the remaining
400 MB of space to be available to other programs. It’s important to make sure you configure the
software to claim an appropriate amount of space. If your recording ends up needing more than
500 MB, the software begins dynamically finding new chunks of space on the hard drive to put
the extra data. In this situation, it’s possible for dropouts to happen if sufficient space cannot be
found fast enough. The problem is compounded by multitrack recording. Imagine what happens
if you're recording 24 tracks of audio at one time. The software has to find 24 blocks of space on
the hard drive that are 500 MB in size. That’s 12 GB of free space that needs to be immediately
and exclusively available.
One way to avoid problems is to dedicate a separate hard drive other than your startup
drive for audio capture and data storage. That way you know that no other program will attempt
to use the space on that drive. You also need to have a hard drive that is large enough and fast
enough to handle this amount of sustained data being written, and often read back. In today’s
technology, at least a 7200 RPM, one terabyte dedicated external hard drive with a high-speed
connection should be sufficient.
5.1.6 Digital Audio File Types
You saw in the previous section that the digital
audio stream moves through various pieces of
software and hardware during a recording
session, but eventually you’re going to want to
save the stream as a file in permanent storage.
At this point you have to decide the format in
which to save the file. Your choice depends on
how and where you’re going to use the
Audio file formats differ along a
number of axes. They can be free or proprietary, platform-restricted or cross-platform,
compressed or uncompressed, container files or simple audio files, and copy-protected or
unprotected. (Copy protection is more commonly referred to as digital rights management or
Proprietary file formats are controlled by a company or an organization. The
particulars of a proprietary format and how the format is produced are not made public and their
use is subject to patents. Some proprietary files formats are associated with commercial software
for audio processing. Such files can be opened and used only in the software with which they’re
associated. Some examples are CWP files for Cakewalk Sonar, SES for Adobe Audition
multitrack sessions, AUP projects for Audacity, and PTF for Pro Tools. These are project file
formats that include meta-information about the overall organization of an audio project. Other
proprietary formats e.g., MP3 may have patent restrictions on their use, but they have openly
Aside: In our discussion of file types,
we’ll use capital letters like AIFF and WAV
to refer to different formats. Generally
there is a corresponding suffix, called a file
extension, used on file names e.g., .aiff
or .wav. However, in some cases, more
than one suffix can refer to the same basic
file type. For example, .aiff and .aif, and
.aifc are all variants of the AIFF format.
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