Chapter 21: Audio/Visual Devices^553
RA or RAM
RA or RAM file formats are RealAudio files, a streaming audio format developed by
RealNetworks. The quality of RealAudio files varies with the speed of the Internet con-
nection. RealAudio files targeted for high-bandwidth connections like DSL or T1 can ap-
proach CD quality, while files designed for modem downloads are similar to the quality
of an AM radio signal. RealAudio files require a dedicated RealAudio player or browser
plug-in for playback.3-D Audio
3-D audio is an emerging sound playback technique used to give more depth to tradi-
tional 16-bit or higher stereo sound. Typically, it is reproduced with a special device that
adjusts the sound coming from the speakers to create the impression that the speakers are
further apart. 3-D audio devices are particularly popular where speakers tend to be small
and close together.WAV
The WAV (waveform audio) file format, developed by Microsoft, is the de facto file for-
mat standard for nonstreaming audio files. It is supported on nearly all platforms and re-
quires no special software beyond that associated with nearly all sound cards. A WAV
file contains a digital representation of an analog sound signal and like most digital
sound formats, the better the recording quality, the larger the file. WAV files can be very
large. For example, an 8-bit recording can use as much as 1.5MB per minute of original
sound, and a 16-bit recording can require 3MB per minute.WMF
Windows Media File is Microsoft’s answer to RealAudio. Like RealAudio, WMF sound
qualityisbandwidthdependent.WMFfilescanbeplayedbackonWindowsMediaPlayer.Streaming Audio
A very common means of transmitting large audio files over the Internet is streaming au-
dio. The RealPlayer client and the Windows Media Player are the most popular playback
software tools, both supporting streaming audio and video (discussed later in the chap-
ter). Streaming audio, which was specifically designed for the Internet, compresses a
standardaudiofile(suchasaWAVfile)andsendsitasastreamofbitstotheuser.Instead
of waiting to download the entire file before you can hear it, as would normally be re-
quired for a WAV file, the playback software plays back the file as it is received. The qual-
ity of the sound playback is about equal to the radio, provided you have enough
bandwidth to drive the stream without interruption.
Streaming media trades convenience for sound quality, especially when there are many
sounds at the same time. Streaming architectures are able to compress a 10MB WAV file
to less than 300KB, a reduction that allows sound files to be transmitted across the