Digital Sound & Music: Concepts, Applications, & Science, Chapter 1, last updated 6/25/2013
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computer. All of these instrument samples have to be loaded into RAM so they can be instantly
accessible to the MIDI keyboard. For these reasons, you'll probably need to upgrade the RAM
capacity on your computer. A good place to begin is with 2 GB of RAM. RAM is easily
upgradeable and can be increased later on if needed. You can check the system requirements of
your audio software for the specific RAM requirements of each application program.
You also need memory for permanent storage of your audio data a large capacity hard
disk drive. Most hard drives found in the standard configuration for desktop and laptop
computers are not fast enough to keep up with
real-time processing of digital audio. Your
RAM buffers the audio playback streams to
maintain the flow of data to your sound card,
but your hard drive also needs to be fast
enough to keep that buffer full of data. Digital
audio processing requires at least a 7200-RPM
hard drive hard that is dedicated to holding
your audio files. That is, the hard drive needs
to be a secondary one, in addition to your
system hard drive. If you have a desktop
computer, you might be able to install this
second hard drive internally, but if you have a
laptop or would simply like the ability to take
your data with you, you‟ll need an external
hard drive. The capacity of this hard drive
should be as large as you can afford. At CD
quality, digital audio files consume around ten megabytes per minute of sound. One minute of
sound can easily consume one gigabyte of space on your hard drive. This is because you often
work simultaneously with multiple tracks sometimes even ten or more. In addition to these
tracks, there are backup copies of the audio that are automatically created as you work.
New technologies are emerging that have the potential for eliminating the hard drive
bottleneck. Mac computers now offer the Thunderbolt interface with bi-directional data transfer
and a data rate of up to 10 Gb/s. Solid state hard drives (SSDs) distinguished by the fact that
they have no moving parts are fast and reliable. As these become more affordable, they may
be the disk drives of choice for audio.
Before the advent of Thunderbolt and SSDs, the choice of external hard drives was
between FireWire (IEEE 1394), USB interfaces, and eSATA. FireWire that has proven reliable
for real-time digital audio on the Mac operating system. The advantage of FireWire over USB
hard drives is that FireWire is not host-based. A host-based system like a USB drive does not
get its own hardware address in the computer system. This means that the CPU has to manage
how the data move around on the USB bus. The data being transferred must first go through the
CPU, which slows down the CPU by taking its attention away from its other tasks. FireWire
devices, on the other hand, can transmit without running the data through the CPU first.
FireWire also provides true bi-directional data transfers -- simultaneously sending and receiving
data. USB devices must alternate between sending and receiving. For Mac computers, FireWire
drives are preferable to USB for simultaneous real-time recording and playback of multiple
digital audio streams. FireWire speeds of 400 or 800 are fine. These numbers refer to
approximate Mb/s half-duplex maximum data transfer rates. However, keep in mind that mixing
Aside: Early digital audio workstations
utilized SCSI hard drives. These drives
could be chained together in a combination
of internal and external drives. Each hard
drive could only hold enough data to
accommodate a few tracks of audio, so the
multitrack audio software at the time
would perform a round-robin strategy of
assigning audio data from different tracks
to different SCSI hard drives in the chain.
These SCSI hard drives, while small in
size, provided impressive speed and
performance and to this day, no external
hard drive system can completely match
the speed, performance, and reliability of
external SCSI hard drives when used in
digital audio.
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