Traditional uses of audio on the Internet depend mostly on conventional transfer techniques,
meaning a file must be downloaded from a server, usually via FTP,
Gopher, or electronic mail, before hearing it.
Because of this time lapse limitation, audio content providers have
used Internet servers mainly as centrally located storage devices;
archives that can be accessed worldwide. An excellent example of this
use is the Time of The Day
function at Yale University.
Forms of audio common to non-computer media, such as telephony, radio
broadcasts, and tele/videoconferencing, continue on the Internet.
Gradually, computers have incorporated the functions performed by
separate electronic devices around the home and business: facsimile
machines, CD players, telephones/answering machines, televisions/VCRs,
radios, and so on. The functions that require audio input/output are
easily handled by a computer with some additional audio circuitry, a
microphone, speaker(s), and inputs for audio media, such as a CD
player. The audio functions that work across networks, such as
telephony,
broadcast
audio/video, and
teleconferencing, are
dependent also on sufficient bandwidth for success.
Considering the relatively low quality of telephone audio
(approximately that of AM radio), it occupies little bandwidth.
Telephony applications, such as DigiPhone, are able to use the
bandwidth of a modem, 14,400 bits per second, to achieve full-duplex
audio, functionally replacing the telephone.
Telephony applications have practical obstacles to overcome when trying
to replace the phone. First, the computer must be kept on anytime
incoming calls are desired. Second, the other party must be using the
same system (there is yet no computer industry standard, much less
Internet-wide standard, for telephony). Third, a familiar physical
user-interface, analogous to a handset, is not part of the standard
computer configuration. Speakerphone and handset solutions have thus
far been implemented rather clumsily because they must coordinate
several audio inputs and outputs, but have potential for future
success.
Progressive Networks Inc.'s RealAudio, an audio client-server system
that approximates real-time delivery, is
already being used to deliver news broadcasts.
The power of the spoken word can be found recorded in many places, such
as the introductory message by Bill Clinton at the White House WWW page. While the
client is designed to play an audio file as it is downloaded, the server is
optimized for sending many simultaneous streams of audio. By integrating
the player with the Web browser, RealAudio and similar systems take
advantage of established distribution, authoring, and security protocols.
Future plans for the server include live audio feeds in
real-time, broadcasting text along
with the audio stream, and increased capability from hundreds to
thousands of simultaneous streams.
The RealAudio compression algorithm and technical specifications are kept
confidential, although others are developing similar methods (see below).
The sound quality approximates an 8 bit, 11Khz sample, playable over an
14,400 bps modem connection with modest processing requirements. Since
the playback method is not scaleable, the same quality is had on computers
with faster connections and greater processing power.
The DSP Group, Inc. has developed a
similar product called TrueSpeech. TrueSpeech concentrates on compression
algorithms tuned specifically for speech. DSP has decided to offer more
than one compression scheme in the TrueSpeech player, offering options in
sound quality, file size, and transmission speed. Additionally, TrueSpeech
is working toward standardizing it's compression algorithms for
cross-platform use of computer and telephony products.
TrueSpeech 8.5, using a 15:1 compression ratio, is a part of the Windows 95
Internet Explorer
Web Browser, ensuring widespread use. The DSP Group plans to develop a
TrueSpeech server to be used much like the RealAudio server. For now,
Windows 95 users are able to encode audio and save it as WAV files.
Presumably, these files have the advantage of being played on either
TrueSpeech players or in non real-time with a conventional sound utility,
as opposed to the proprietary RealAudio format.
The Xing Technology Corporation
has released the similar StreamWorks product. The major differences being
the capacity for live broadcast feeds and
the international standard MPEG compression. Also, it is designed to
operate over TCP/IP networks of varying topologies, including Ethernet,
ATM, FDDI, ISDN, T1 and Frame Relay. For this reason, it has uses beyond
the Internet, such as in corporate and educational Wide Area Networks.
More advanced uses of audio on the Internet include teleconferencing.
The great advantage of conferencing over traditional telephony is the ability of
several parties to simultaneously communicate with each other.
Developers have bypassed audio teleconferencing systems, finding enough
bandwidth in the typical modem connection to transmit both audio and
video together . CU-SeeMe, a personal
computer-based videoconferencing client-server system, manages to work audio material
into it's compression scheme along with video. It achieves such
excellent efficiency by using four compression algorithms with a choice
of two different audio sampling rates. All compression functions in
software with modest microprocessor requirements.
CU-SeeMe operates in a client-server configuration: clients transmit
signals to "reflector sites," UNIX-based servers which receive and
re-transmit the signals. This configuration, rather than a
client-client system, allows broadcasting from one point to many, as
well as true multi-point conferencing.
While the ability to videoconference
over TCP/IP connections with no additional cost is attractive, it is unfortunate that the CU-SeeMe protocol is not
compatible with current videoconferencing standards. Conversion between
standard videoconferencing protocols and the CU-SeeMe protocol would
enable most anyone on the Internet to exchange real-time audio and video
with the many installed conventional videoconferencing systems.
Next Section:
Tradional Uses
Advanced Uses
Audio as an Interface to The Computer: An Introduction to Human-Computer Interface
Design