Web Audio Needs Compression!
this complicates things a little
Below, I'll
outline what is going on.
CD quality mono audio uses
a lot of data. It's about 5MB per minute.
For storage and playback on
your hard drive, that's not a problem.
For distributing via the
web or for emailing, it's been a big problem for a long time! Dial-up internet
connections ruled the planet not so long ago. On those, it might take 16
minutes at 5KB/sec to download 1 minute of audio!
So, much corporate effort
went into ways to compress audio, without losing too much quality of listening
enjoyment. That's why ".mp3" got to be famous, as a means of reducing
file sizes by over 75% for music.
Internet speeds improved,
but portable players took off, so folks still needed compression to fit more
music on their device.
Audio Compression
is HERE to STAY!
Folks will always want
speed and bulk storage so compression will always be needed. They will prefer
to stretch their bandwidth (as this improves) with better video quality!
"Mp3" is what's
called a "Codec"; a way of "squashing" audio data into a
form that can be "unsquashed" for listenable sound. There are dozens
of codecs!
Mp3 had competition.
Microsoft introduced their own "Windows Media Audio" (.wma) format. Apple
has supported a format they think works best for music. It's "AAC"
which also comes with files extensions ".m4a" and ".m4b".
Qualcomm did a massively
compressed codec with files ending in ".qcp"
Most codecs are corporate
products that require licensing fees for programs that will encode that way.
Some codecs are "Open
Source". They have no licensing fees and programmers can study the code to
see if they can improve it. Ogg is the dominant of these. (File extension;
".ogg" ".oga")
What it means for
you!
When audio is posted to the
web, your web browser must know what to do when you open it. All browsers
handle some kinds of file "natively" (within themselves), such is the
case with pictures having the ".jpg" extension.
As we've seen, web audio
has many codecs, and it would make web browsers very bulky/slow/unreliable if
they attempted to play type natively.
There are two main
solutions:
(i) "Plug-ins"
are added to browsers, which can be added, updated (or deleted). The plug-in
gets called to play files it has been allocated.
(ii) The browser asks the
user what to do with the file, usually in the form of offering to download it
and play with program "x" that you have already installed.
So, to listen to the audio
with a particular browser, that browser must either have the correct plug-in,
or you must have a program on your computer that plays that type of audio file.
Unfortunately,
browsers perform differently, even the same browser on different OS's
Users who intend to utilise
web audio will need to think about this. It may be necessary to switch browsers
between doing your banking and listening to web audio.
Some general observations
can be made:
(1) .mp3 is the most widely
supported codec. I don't know of a browser that doesn't support it "out of
the box".
(2) AAC/m4a/m4b is gaining
ground, probably be cause Apple is pushing it so hard as the standard for their
mobile devices.
(3) .ogg is the most
interesting, with the brightest future, Worldwide, where "corporate
formats" do not have either public or Government support. Ogg now plays
natively in the Google "Chrome" browser for Windows.
Check how
different codecs work for you
Below are listed versions
of the same one minute audio recording in the described codec. As I've said above,
for you, with your browser, OS and installed audio programs, some will work,
some will likely not.
The solution for
you may be to download & install audio playback software you don't have.
Not all of these
files might play for you.
This is a reminder
that web audio is a "setting" that must be adjusted!
|
Compression codec |
Extension |
Data per minute |
Comment |
|
.wav |
5169 KB |
CD quality
voice |
|
|
.mp3 |
353 KB |
||
|
.aac |
492 KB |
||
|
.m4b |
492 KB |
"Talking Book" version played by iTunes |
|
|
.ogg |
499 KB |
||
|
.spx |
230 KB |
||
|
.wma |
40 KB |
||
|
.qcp |
103 KB |
You'll
need their player to listen! |
|
|
.3gp |
48 KB |
* Note: Compression rates are user-variable.These are
sample rates. These intensities of compression are unsuitable for music! How
does the 40 KB .wma file sound to you? Compare with the 3G version, (which can be recorded and emailed from Josh's
Samsung Android phone!)
** Note: The above files are configured to "Download
& Play". Consequently, the
listener can easily save their own copy. For many situations, this is
desirable. However, when the author want to retain ownership of the audio, techniques
of "Streaming" will likely be used, in which case the computer's
sound card processes the sound but does not keep a copy of it.
Separately from this issue,
streaming started in the days of minimal bandwidth, when users did not want to
wait for a file to download (possibly many minutes later), before they could
start to hear it.
With the huge increase in
bandwidth in the last few years, "Download & Play" is usually a
minor problem. If longer audio durations are to be deployed,
"Playlist" techniques are
relevant, whereby the part(s) the listener actually needs are downloaded.
"smil" and "m3u" offer such delivery.
More information on setting your computer for web audio will
follow.
For samples of Open Source "Ogg Theora"
video, click HERE.