Audio Guide
for Web Developers
Introduction
This is a guide to the use of audio files in your web pages.
It explains the most common file types and their uses, it explains
how to code audio links in your pages, it lists major sources
of audio files and clips, and it gives you brief copyright guidance
as to what you can and should do with audio files.
Equipment Requirements for Audio
Although most computers come with a built-in speaker, it is of
low quality, and audio files will generally not play through it.
To play music quality sound files, it requires a sound card and
speakers attached to the card. Many notebooks now come with a
built-in sound card and small speakers in the notebook, which
can be supplemented with plug-in external speakers. Computers
sold as multimedia machines usually come with a sound card and
speakers included in the price. The earliest sound cards were
labelled 8-bit. Then came higher quality 16-bit cards, which refers
to the capability to produce high quality, wide audio bandwidth
sound. The terminology is confused by new cards with 32 and 64
in their name, which refer to 32-voice and 64-voice synthesizers.
Probably the best known maker of sound cards is Creative
Labs, maker of SoundBlaster cards.
Audio File Types
Sound files, by their nature are quite large. Types that must
fully load before they can play can cause long waits across dial-up
speed lines. Most types of sound files are based on taking very
frequent samples of the complex sound waves and digitally recreating
those sound waves during playback. The faster the sampling, the
higher the quality of sound, but the larger the file. Low quality
files are typically sampled 11,000 times per second. Medium quality
is sampled 22,000 times per second, and high quality is 44,000
times per second. The low quality is akin to telephone sound,
and not very good for listening to music. The high quality is
similar to FM radio. File sizes may be reduced somewhat by compression
techniques.
The earliest types on the Internet, first used with unix computers,
use the .au and .snd extensions. These are apt to be the largest
files for a given length of audio. Later sound files use the extensions
.ai, .aif, .mp2 or .mp3, and .wav. Most modern browsers either
have the capability to play these built in to the software or
can play them with plug-in software, readily available from Netscape
or Microsoft.
If your modem and connection are fast enough, it is possible
under good conditions to feed a low to medium quality signal to
you fast enough to play in real time over a dial-up connection.
RealAudio was the first
company to produce streaming audio files and broadcast of live
events. These files have the .ra extension, and require you to
download the RealAudio or RealPlayer software(the latter combines
a streaming video capability, too) from the
RealAudio site or buy it in a store. There are other forms
of streaming audio appearing now, too, such as the audio components
for QuickTime, Shockwave, and Streamworks.
MIDI, another type of sound file uses a resident library of
instrumental sounds from your sound card. This technique is called
wave table synthesis. The files, instead of reproducing sound
waves based on sampling, feed information to the software and
sound card on pitch, duration, instrument or type of sound, and
other technical characteristics of the sound. The card pulls the
prerecorded instrumental sounds from its wave table. These files
can be much smaller than those based on sampling, even with many
instruments. If your sound card supports MIDI (Musical Instrument
Digital Interface) files (with the .mid extension), you can play
MIDI files. Quality may vary greatly, depending on the sound card
and you can hear very different sounds from different computers.
At its best, it can be very, very good. At its worst, it is horrible.
It is very popular, though, and large libraries have been built
up of MIDI files. See Sources below. MIDI, as an audio standard
for musicians, can be used with keyboards and synthesizers independent
of computer systems, too.
Check to see if your system is set up to play the types below
by trying the examples at these pages:
Coding Sound in HTML
The simplest way to call a sound file is to simply put a link
to the file. Depending on your browser and configuration, it will
either invoke your operating system's basic player software, player
support built into the browser, or a plug-in that provides the
player capability. If you want to control what plug-in is used
to play the sound file, you need a more sophisticated call. As
an example of the simplest format, the line of HTML code below
will call up the file mysong.mid from the current directory with
any browser. Note that you can play any sound file with this command
format, not just MIDI files:
<a href="mysong.mid"> Play My Song </a>
It is also possible to embed a file into the html code for a
page so that it will play in the background. Netscape introduced
the EMBED tag and Microsoft the BGSOUND. With the newer browsers,
both commands can be used and each browser will ignore the other's
command. The examples shown here use MIDI files, but you can substitute
other file types with the same results. Here are the paired commands
to call a MIDI file. In the first example, the Netscape EMBED
call forces the use of the Crescendo
MIDI player plug-in. The second example allows any MIDI player
to take effect instead of the Crescendo. The companion MSIE BGSOUND
call does not specifically call Crescendo.
Example 1:
<EMBED TYPE="music/crescendo" SONG="mysong.mid"
HEIGHT=16 WIDTH=16 AUTOSTART=true LOOP=false> <BGSOUND SRC="mysong.mid"
LOOP=1>
Example 2:
<EMBED SRC="mysong.mid" AUTOSTART=true LOOP=false>
<BGSOUND SRC="mysong.mid" LOOP=1>
Notice that both EMBED and BGSOUND include a LOOP parameter.
Set to "false" and "1" respectively, the file
does not repeat. Set to "true" and "-1" or
"INFINITE", it repeats endlessly until the page is abandoned
or the music turned off. BGSOUND also permits a specific number
of repetitions.
Then Microsoft introduced ActiveX and OBJECT tags, and the most
general answer that gives the most control is to put an EMBED
tag inside OBJECT tags. If you want to try this somewhat more
sophisticated approach, the formats that work are explained and
illustrated for the Crescendo MIDI player's guide to Embedding
Plugins.
MSIE 4.0 added support for the EMBED command. If you are willing
to omit support for earlier versions of MSIE, you can just use
the EMBED command as shown in the examples above.
Different versions of Netscape and MSIE have responded in different
ways to this code. There is a JavaScript approach that will work
with all these (as long as your browser supports JavaScript) at
Crescendo's JavaScript
for both Netscape and MSIE page. Try it, if you want to cover
as many bases as possible.
Another excellent source that explains JavaScript approaches
to playing music is Martin Griffith's article Writing
a MIDI HiFi System in JavaScript at developer.com.
Sources of Sound Files
Just Jazz.
A superb collection of Jazz MIDI files.
TuDogs:Free Music.
A rated selection of pointers to music source sites. Mostly MIDIs.
Music Selection Resources
on the WWW. A large selection of music and music-related links,
briefly annotated.
Classical MIDI Archives.
The definitive classical MIDI collection.
Worldwide
Internet Music Resources. A large collection of music resources
from the Indiana U music library, including some music clips.
The All-Music Guide.
A bit of a misnomer, since it is very weak on classical and show
music, but very strong in popular music.
Copyright Guidance When music is played, there are two
copyright considerations. Unless the work was written in a previous
century, somebody probably owns the copyright to the music (and
lyrics, if any). For recorded music, the performing artist or
artists also hold a performance copyright. For television, radio,
and club performances, most of the copyright fees are handled
by ASCAP and BMI.
Performance rights for recordings are handled by RIAA.
They are beginning to vigorously enforce copyright for web pages,
too. Web licensing is a new field, but RIAA, ASCAP and BMI are
dogged pursuers of copyrights, and they can't be ignored. BMI
has a MusicBot that searches the nets looking for violations.
Not long ago, there were two major classical music MIDI sites.
One pulled all the 20th century composer works with a note that
it was for copyright reasons. The other didn't, and it recently
disappeared without notice.
The National Music Publishers Association (NMPA) and their licensing
arm, the Harry Fox Agency have been vigorously cracking down on
websites that post unlicensed copyrighted works. Many MIDI sites
have been closed recently.
To dispel a few common misconception, you have no fair use right
to put a recording on your web pages. And although some have suggested
that short clips under 30 seconds are all right to use, that has
not been established in the courts.
Reprinted with permission
from author Walt Howe,
whose Web site contains
good information on utilizing the digital medium.
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