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 4 bit.

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 this.

"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 latency".

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 interrupted (Shockwave).

"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?

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 (see here).

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.

"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 files.

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.

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 protocols.

"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 what happens:

The server tells the browser something about the special file (this message is called a "MIME-type").

1. 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.

2. 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.

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 use Director.

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).

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.

"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).

"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 of soundcards.

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.