3

Interleaved Versus Split Stereo Audio Files
Digital audio can send a stereo signal within a single stream by interleaving the digital
samples during transmission and deinterleaving them on playback. The way the signal
is stored is unimportant as long as the samples are properly split to left and right channels
during playback. With analog technology, the signal is not nearly as flexible.
Split stereo files are two independent audio files that work together, one for the left
channel (AudioFile.L) and one for the right channel (AudioFile.R). This mirrors the traditional
analog method of one track per channel (or in this case, one file per channel).
Digital Audio
Digital audio recording works by recording, or sampling, an electronic audio signal at
regular intervals (of time). An analog-to-digital (A/D) converter measures and stores each
sample as a numerical value that represents the audio amplitude at that particular moment.
Converting the amplitude of each sample to a binary number is called quantization. The
number of bits used for quantization is referred to as bit depth. Sample rate and bit depth
are two of the most important factors when determining the quality of a digital audio
system.
Sample Rate
The sample rate is the number of times an analog signal is measured—or sampled—per
second. You can also think of the sample rate as the number of electronic snapshots
made of the sound wave per second. Higher sample rates result in higher sound quality
because the analog waveform is more closely approximated by the discrete samples.
Which sample rate you choose to work with depends on the source material you’re
working with, the capabilities of your audio interface, and the final destination of your
audio.
For years, the digital audio sample rate standards have been 44,100 Hz (44.1 kHz) and
48 kHz. However, as technology improves, 96 kHz and even 192 kHz sample rates are
becoming common.
When usedAudio sample rates
These lower sample rates are used strictly for multimedia files.8 kHz-22.225 kHz
32 kHz is generally used with 12-bit audio on DV.32 kHz
This sample rate is used for music CDs and some DAT recorders.44.1 kHz
Almost all digital video formats use this sample rate.48 kHz
A multiple of 44.1 kHz. This is useful for high-resolution audio that
needs to be compatible with 44.1 kHz. For example, if you eventually
plan to burn an audio CD, this sample rate is a good choice.
88.2 kHz
A multiple of 48 kHz. This is becoming the professional standard
for audio post-production and music recording.
96 kHz
497Appendix B Audio Fundamentals