The new DV Format (digital video format) is interesting in that it has two different options for digital audio: two channels of 16-bit 44.1 or 48kHz audio, or four channels of 12-bit 32kHz audio. The first one is similar to that used by audio CDs, and is great for commercial video releases and professional applications. It's the second format that offers some interesting options and tradeoffs available with digital audio.

Four-channel audio allows you to record the location sound that occurs while you're shooting the video, and then later add music, sound effects, or narration on top. The problem is how to shoe-horn four channels into the same space reserved on tape for two. If you drag out a calculator and run the numbers mentioned above, you see how the math works out: two channels x 16 bits x 48,000 samples per second = 1,536,000 samples per second. Four channels x 12 bits x 32,000 samples per second = 1,536,000 as well. The DV format can store either in the same amount of space.

So what's the tradeoff? Bandwidth and resolution. Remember our method for dividing the sampling rate by two to get the highest frequency the system can record? Notice that 32,000 Hz/2 = 16,000 Hz, which even under the most optimistic conditions is starting to crimp in on the upper limit of our hearing. This is not great fidelity, but in practice is still better than most other consumer videotape formats--let alone TVs--can comfortably handle. And what about 4096 values (12 bits per sample) versus 65,536? Again, not perfect. But in this case the DV system distributes the 4096 numbers in a special way to use more of them for lower sound levels. This reduces apparent quantization distortion and noise. All in all, not that bad a set of compromises.

It's inevitable that we'll be seeing more and more media--pictures, words, video, and sound--in digital form. Dealing with digital audio and video may seem new to many of us, but it certainly is the future--one that offers us a lot of creative options.