Digital Audio in Windows Vista

The reputation Windows has as an audio playback and editing platform has been, not to put too fine a point on it, abysmal. There have been some improvements over the years. For example, the early audio infrastructure (often called the audio stack) seen in Windows 3.1 (16-bit) and Windows 95 (32-bit) supported only one audio stream at a time, but Windows 98 enabled multiple playback streams using the Windows Driver Model architecture.

However, Windows audio has always suffered from three major problems:

  • A poor interface for controlling audio and for troubleshooting audio problems. Tools such as Volume Control, the Sound Recorder, and the Control Panel Sounds and Audio Devices icon had difficult interfaces and limited functionality, and clearly weren't geared for the day-to-day audio tasks that users face.
  • Poor quality playback and recording. The Windows audio stack has always been merely "good enough." That is, audio in Windowsparticularly playbackwas constructed to give the average user a reasonable level of quality. However, the default Windows audio had nowhere near the fidelity audiophiles and professional audio users require, so these users spent much of their time working around inherent audio limitations (or giving up on Windows altogether and moving to the Mac).
  • Poor reliability, to the point that audio glitches are one of main causes of system instability. The problem here has been that much of the audio stack code runs in the sensitive Windows kernel mode, where a buggy driver or process can bring down the entire system.

To address these problems, the Vista audio team completely rewrote the audio stack from the ground up. That's good news for both regular users and audiophiles because it means the Vista audio experience should be the best yet. Completely revamping the audio infrastructure was a big risk, but the aim was to solve the three previous problems.

We'll have to wait and see if Microsoft accomplished this ambitious goal (not all the new audio features were available as I wrote this), but on paper, things look promising:

  • New tools for controlling the volume, recording sounds, and setting sound and audio device properties offer a much improved user interface geared toward common user tasks and troubleshooting audio problems.
  • The new audio stack offers much higher sound quality.
  • Most audio code has been moved from kernel mode to user mode, which should greatly reduce audio-induced system instabilities.

The Volume Control tool in previous versions of Windows is a good example of poor audio system design. When you opened Volume Control, you were presented with a series of volume sliders labeled Master, Wave, Line In, CD Player, Synthesizer, Aux, and more. For the average user, most of these labels were, at best, meaningless and, at worst, intimidating. What on earth does the Aux slider control? What's the deal with Line In?

Most people ignored all the sliders except Master and just used that slider to control playback volume. However, that Master slider had problems of its own. For example, suppose you're waiting for an important email message, so you set up Windows Mail to play a sound when an email message comes in. Suppose further that you're also using Windows Media Player to play music in the background.

If you get a phone call, you want to turn down or mute the music. In previous versions of Windows, muting the music playback also meant muting other system sounds, including your email program's audio alerts. So while you're on the phone, there's a good chance that you'll miss that important message you've been waiting for.

The Windows Vista solution to this kind of program is called per-application volume control. This means that Vista gives you a volume control slider for every running program and process that is a dedicated sound application (such as Windows Media Player or Media Center) or is currently producing audio output.

In our example, you'd have separate volume controls for Windows Media Player and Windows Mail. So when that phone call comes in, you can turn down or mute Windows Media Player while leaving the Windows Mail volume as is, so there's much less chance that you'll miss that incoming message.

In the old Volume Control tool, when you adjusted the Master slider, the other volume sliders remained the same. In the Vista Volume Control tool, when you move the speaker volume slider, the program sliders move along with it. That's a nice touch, but what's even nicer is that the speaker volume slider preserves the relative volume levels of each program. So if you adjust the speaker volume to about half its current level, the sliders in the application mixer also adjust to about half of their current level.

Volume Control also remembers application settings between sessions. So if you mute Solitaire, for example, it will remain muted the next time you start the program. The new volume control also supports metering, in which the current audio output is displayed graphically on each slider.

This metering appears as a green wedge that grows taller and wider the louder the sound signal is. This is very useful for troubleshooting audio problems because it tells you whether a particular program is actually producing audio output. If you have no sound from a program, but you see the metering in program's volume slider, the problem lies outside of the program (for example, your speakers are turned down or unplugged).

Sound Recorder

The Sound Recorder accessory first appeared in Windows 95 and has remained a part of Windows ever since. Unfortunately, the Sound Recorder in Windows XP is essentially the same program as the original version, which means the program's annoying limitations haven't changed, either:

  • You can save your recording only using the WAV file format.
  • You can record only up to 1 minute of sound.

Windows Vista comes with a completely new version of Sound Recorder that does away with these limitations. For example, you can save your recording using the Windows Media Audio (WMA) format, and there is no limit (other than available hard disk space) to the length of the recording.

Having no recording limit might sound dangerous, but the new Sound Recorder captures WMA audio at a bit rate of 96Kbps, or about 700KB for a 1-minute recording. Compare this to a 1-minute CD-quality recording using the old Sound Recorder, which could easily result in a 10MB file!

Audio Devices and Sound Themes

The Windows Vista replacement for the Control Panel Sound and Audio Devices icon is Audio Devices and Sound Themes (in the Control Panel, select Hardware and Sound, Audio Devices and Sound Themes).

The Audio Devices tab shows the playback and recording devices on your system. The first thing to notice is that you now have a visual reminder of the default devices for playback and recording in the form of a green checkmark icon. The checkmark means that the device is the default for all uses.

However, you can also designate a device as the default for specific uses. If you right-click a device and then click Set as Default For, you get a list that includes All Uses, General Usage, Music and Movies, and Speech and Communications. (Here, "General Usage" means any use that doesn't involve movies, music, speech, and communications.)

Windows Vista also implements a more extensive collection of properties for each device. Double-clicking a device displays a property sheet. The properties you see depend on the device. Here's a summary of the tabs you see when you open the default playback device (although note that not all audio playback devices support all of these tabs):

  • General Change the name and icon for the device.
  • Configuration Specify your speaker setup (Stereo, Quadraphonic, 5.1, and so on), and then test and balance your speakers.
  • Tone Set the bass and treble balances.
  • Other Configure the device for digital output only.
  • Mixer Set the volume levels.
  • Format Set the default playback format and latency.