Sound, Video and Animation
All right, so you made it
through "Internet 101", but you still have no clue why
it is that some home pages start partying five seconds
after you hit them, while others are still dead silent
and basically empty after your second cup of coffee?
Look no further! The answer
to this and many other Web mysteries is here.
If it's not (or not yet),
hit the link to firstname.lastname@example.org
and submit your question. You will receive a FREE answer
in your e-mail before long!
Current subject list:
|How "big" is a sound?
A digital sound is actually quite big: Each
second of a stereo CD contains 1,411,200 single
informations (bits), or 176,400 Bytes, or 172.25
KBytes. On a computer this type of sound usually
comes as a file with the extension "wav" on
the PC and "aiff" on the Mac. Downloading a
second of CD quality sound would last about
2 minutes on an average Internet connection
with a 28 k modem. (A 14 k modem takes about
twice as long...)
The same file type can also store sound information
in lower quality. Three things can get worse:
Stereo can become Mono (1 channel instead of
2), the "resolution" can be reduced from 16
bit to 8 bit or even 4 bit, and the "sample
rate" can be reduced from 44.1 kHz to 22 kHz,
11 kHz or 5 kHz.
Any of these reductions are "divide by 2" operations
- and that's what will happen to the file size!
One second of sound (wav or aiff) in mono, 22
kHz, 8 bit is about 21.5 Kbytes. One second
in mono, 5 kHz, 4 bit is about 2.7 Kbytes.
Doesn't sound big? True - but doesn't sound
good either! And now consider this: 2.7 Kbytes
is pretty much a dream performance of a 28 k
modem connection to the Internet! It happens,
but not very often. Realistically speaking,
a "good" connection with a 28 k modem makes
something between 1.5 and 2.3 Kbytes per second
- not even enough for the bad sound at 5 kHz
While audio files can only become smaller by
"compressing" them (trying to put more information
in the same space) there is one sound format
that's naturally slim and trim: MIDI. The size
of a MIDI file depends somewhat on how much
action is in the music. Starting at about 100
Bytes per second, you will hardly find a MIDI
file that's more than 500 Bytes per second!
Yep, that's small.
So, why not stuff all the audio files into
MIDI format and use this for the Internet? There's
a problem: MIDI can't be recorded like audio,
it must be "programmed", and it's limited to
sounds that a "sound module" or "sound card"
can generate. That means no human voices, no
natural instruments - nothing that can only
be recorded with a microphone or something like
|What is "streaming"?
"Streaming" on the Internet is when you don't
have to wait until (e.g.) a sound file is completely
downloaded before you can begin to listen to
it. You can tell that it makes a lot of sense
to use "streaming" with anything that happens
in time, like audio, video and animation.
Let's look at an example: say you have a sound
file of two minutes. Say it would take 5 minutes
to download the entire file over your modem.
Without "streaming" you'd have to wait 5 minutes
until you can listen to the sound. With "streaming"
your computer can start to play the sound after
about 3 minutes. There's still enough time to
download the rest of the file without having
to stop the music!
While you can save 2 minutes in this example,
most people don't even want to wait for 3 minutes.
For a start within seconds and for live radio
or video on the Internet, the sound or video
files have to be so small that their download
time is not longer than their playtime.
"Streaming" multimedia files always target
a specific connection speed. You can say a file
"streams on a 28 k modem connection". This means
that with a 28 k modem the file can start to
play within seconds after the user hits the
play button. With the same file and a slower
Internet connection you'd have to wait for a
while before you could start the sound. This
amount of time is sometimes referred to as "streaming
Big difference: Some multimedia players can
automatically figure out how long they have
to wait before they can start the multimedia
file (RealAudio, VivoActive). With others the
multimedia files have to be programmed in a
special way to avoid that the player (or browser)
starts them too early so that they have to be
|What is "bandwidth negotiation"?
"Bandwidth negotiation" is a RealAudio term.
The "RealAudio server" can deliver different
versions of a sound file to the same hyperlink
- depending on the bandwidth of the network
(Internet) connection. The idea is that someone
with an ISDN connection to the Internet can
get a better quality version than someone with
a 28 k modem.
You say: "Why can't I just put two links on
my page, one saying 'Click her if you have a
28 k modem', the other one 'Click here if you
have an ISDN line'?" You're right, that would
work, but "bandwidth negotiation" is a lot more
elegant, isn't it?
|What's the difference between MIDI and Wave?
MIDI isn't really sound! MIDI is a bunch of
commands that tell a compatible sound module
or sound card which sounds it has to generate.
Although this seems to be rather complicated
if you consider a whole piece of music, the
amount of data that's necessary to do this is
incredibly much less than in an audio recording
of the same sound! The MIDI file is about 500
times smaller than a CD quality recording of
the sound that the sound module generates.
If you want to play a MIDI file on a computer,
you need a "wavetable enhanced" sound card on
a PC, while Macs come with a solution that gets
better sound from the same MIDI file: Quicktime
turns the MIDI file into a Quicktime "movie"
(no pictures, sorry). The sound quality is about
the same as from a decent studio sound module.
Drawback: You have to download the MIDI file
from the Internet first (save to disk), then
start Quicktime and convert the file.
"Wave" is the common name of a sound file with
the extension "wav" (on the PC). The Mac format
that does about the same is "aiff". Wave files
and aiff can store audio in different qualities
|Why are Internet videos blurry?
Video files that work on the Internet are heavily
compressed. The frame rate is brought down dramatically,
and the picture information in each frame is
reduced, too. For example: The RealVideo format
that is optimized to stream on a 28 k Internet
connection has a frame rate of about 0.25 per
second. That's one frame every 4 seconds! Now,
compare this to a video frame rate of 30 frames
per second on your VCR.
The "RealVideo encoder" kind of "smears" subsequent
frames of the original video into each other
to reduce the frame rate. That's how it gets
blurry. Rule of thumb: The more motion, the
blurrier the Internet video. It's pretty much
the same with other common encoders.
|What is "RealAudio"?
"RealAudio" is a registered trademark of RealNetworks
(formerly known as Progressive Networks). RealAudio
consists of three software components: a player/plug-in,
an encoder, and a server. The RealAudio files
have the extensions "ra" for RealAudio, and
"rm" for RealMedia - these are usually video
RealAudio uses several encoding schemes for
audio and video, which optimize the file for
14 k modems, 28 k modems, ISDN etc., respectively.
Each encoding scheme produces files that are
small enough to stream on the targeted Internet
connection. The slower the target connection
the worse the sound.
There are two ways to play a RealAudio file:
You can use an external player application,
the RealPlayer. This brings up a small window
with the player controls on top of the browser
window. Once the RealPlayer is launched you
can minimize its window or just click on the
browser window to bring it to the top, and the
RealPlayer will operate in the background. You
can continue to browse, and the RealPlayer will
not stop playing until the sound file is finished
or you stop it manually.
The other way is to play RealMedia files (RealAudio
and RealVideo) directly in the browser window.
This requires a "plug-in" for Netscape Navigator
or an "ActiveX control" for Microsoft Internet
Explorer. The player controls can be displayed
in the browser window, or hidden. The file can
start to play automatically when the page loads,
or after the user starts it manually. In this
mode, if you load another page into your browser,
the audio or video file will stop playing.
The "RealAudio server" is required if you want
to broadcast live programs over the Internet
(and use RealAudio). The server also features
"bandwidth negotiation". Otherwise
a standard http-server can be used to deliver
streaming RealMedia files.
|What is "pseudo-streaming"?
RealMedia files can be delivered by a server
in two different ways: The server can just deliver
them as it delivers any other files (this is
called "HTTP-protocol" or "HTTP-stream"), or
"RealAudio server" software can be used on the
server (this is called "PNM-protocol" or "Network-stream").
"Pseudo-streaming" is a discriminating name
for HTTP-stream. It was invented by the RealAudio
promotion to suggest that you need to use the
RealAudio server if you want to get "real" streaming.
Here's a free translation: "Streaming RealAudio
files without using RealAudio server software".
That's all there is to it!
The RealAudio server actually has some special
features that cannot be achieved (in RealAudio)
without it. Regarding "streaming"
we cannot find a difference between the two
|Why do I need "plug-ins" for sound and multimedia?
"Plug-ins" are part of the browser architecture
in Netscape Navigator. They enable Netscape
Navigator and compatible browsers to handle
files that they could not play or display otherwise.
When you request such a file from a server here's
The server tells the browser something about
the special file (this message is called a "MIME-type").
- If you have the plug-in:
The browser finds the respective
plug-in and loads it from your hard disk
into memory. The plug-in displays the file
in the browser window.
- If you don't have the plug-in:
The browser doesn't find the respective
plug-in and is puzzled about what to do
with this file. The browser will display
a box with a little puzzle piece in the
center. If you click on the puzzle piece
you get a prompt that lets you choose to
go to a place where you can download the
plug-in - or not.
Most PC versions of Microsoft Internet Explorer
use "ActiveX controls" instead of plug-ins.
While the basic purpose is the same, ActiveX
controls are easier to download and install.
The entire process happens in the background.
You get a prompt to allow download and installation,
and that's it!
Sadly enough, there is actually not a single
sound or multimedia format that could be displayed
equally on different computer systems and browsers
without plug-ins or ActiveX controls.
|What is "Shockwave"?
Shockwave is the sound and multimedia format
of Macromedia. On the Internet you will mostly
find files that are made with "Director", a
very powerful multimedia authoring program.
Unfortunately, the browser add-on that is required
to view "Director movies" is rather big - so,
it takes a while to download and install it,
but you will be rewarded with a number of very
aesthetic and entertaining Internet sites that
Another up and comming Shockwave authoring
program is "Flash". Flash is one of the first
Internet animation programs that's vector based.
This opens up the possibility to create full-screen
animation with high quality graphics and pictures.
If you haven't seen our Multimedia-Show
yet, you should do that now to experience the
power of Flash! As opposed to Director, Flash's
browser add-on is rather small (170 Kbytes).
|How compatible is MIDI?
If the question is: "What systems can play
MIDI?", the answer is "very compatible". If
the question is "Will it sound the same?", the
answer is: "You'll get the same idea, but the
actual sound can be very different."
As for the other multimedia files on the Internet
you need a browser add-on (plug-in or ActiveX
control) in order to play MIDI. Microsoft Internet
Eplorer can use the built-in media player of
Windows to play MIDI. Most MIDI plug-ins work
only with a soundcard that is wavetable synthesis
enhanced. Most PC soundcards have that feature
-- in different grades of perfection.
On the Mac MIDI files can be transformed into
Quicktime "movies" (with sound only). This process
cannot happen in real-time. You have to download
the MIDI file and start it from your hard disk.
This will launch Quicktime. The sound quality
of this process is far superior to wavetable
synthesis! The plug-in "Beatnik" carries the
sound quality of the Mac into the browser, and
even onto the PC (with Netscape 3.01 or better!)
Among the plug-ins/ActiveX controls that battle
on the MIDI sector, "Crescendo" and "Beatnik"
are the most attractive. See more information
in their separate sections.
|What is "Crescendo"?
"Crescendo" is a plug-in and ActiveX control
which enables MIDI files to "stream". If you
want to stream your own MIDI files, you need
a Crescendo "key" that makes one directory on
your server a streaming directory. The key is
affordable for personal Web sites, and kind
of expensive for commercial sites.
The streaming function has still some problems
as of now, most MIDI fles would need some re-programming
to stream completely (Crescendo cuts something
off at the head and tails of regular MIDI files).
|What is "Beatnik"?
"Beatnik" is a general sound plug-in, that
takes care not only of MIDI files, but also
of all kinds of standard sound formats such
as wav, aiff, au. Beatnik also has its own sound
format: "rmf" - rich music format. With this
you can create sound events on mouse overs and
background music or jukebox applications.
Beatnik uses the enhanced sound features of
a Mac to play all these sound files. It even
manages to bring this superior sound quality
to the PC by not using the wavetable synthesis
The Beatnik plug-in is extremly useful if you're
using Netscape (3.01 or better) on PC or Mac,
because it takes care of a whole bunch of sound
formats that you encounter on the Web. Beatnik
is not yet available for Microsoft Internet
Explorer. The rmf sound format can only be created
on a Mac so far.
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