Learning Computer Architecture with Raspberry Pi

Chapter 11

Audio

SOUND CAPABILITY ON computers is certainly a significant matter. An old adage in the film and video industry states, “Sound is 70 percent of your production”. Sound accentuates the visual, sets moods, increases excitement, inspires the user and more. Computer games are one great example that demonstrates the importance of sound.

In short, this chapter is an exploration of sound on computers in general and specifically how the architecture of the Raspberry Pi supports music and all sorts of other sound manipulations. We discuss analog versus digital audio, sound over High Definition Multimedia Interface (HDMI), 1-bit digital analog conversion (DAC), both signal and sound processing, and Inter-IC Sound (I²S, a communications protocol for carrying digital audio signals).

We also cover the Raspberry Pi’s onboard sound, both the input and output features. We begin with the basics of sound on computers and a little history.

Can You Hear Me Now?

Right after World War II ended, the first computers were silent—except, of course, for the grinding and clacking of gears in the mechanical computers, the buzzing of power supplies and the plink of vacuum tubes burning out in electronic mainframes. Then there was also the often-colourful language of operators when these monsters crashed due to faulty programs and the lack of operating systems to prevent or recover from the software mishap, necessitating a lengthy reboot.

The “language” we’re referring to is not COBOL or FORTRAN—or, ...