Oct 202004
 

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

Oct 032004
 

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“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).