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Information about MDN's MP3 Audio

Two IBM PC 300s are being used to stream the House and Senate audio. The OS is Windows NT.

The encoder is WinAmp, using two special DLL plugins you can get from Shoutcast (the makers of WinAmp) for doing live MP3 streaming. With these plugins, WinAmp performs functions:

1. It takes the live audio signal (connected to the sound card's line in) and converts the sound to MP3 (Version 2.5 Layer III).
2. Then, it takes the MP3 digital signal and transmits that through a TCP/IP port to the audio server.

The Audio server is Icecast. It's running on two computers -- 168.166.12.80 for the Senate and 168.166.12.81 for the Senate. Both servers are streaming audio on port 8000. Each computer uses an audio stream generated from WinAmp on its own computer.

We are experimenting with what band width provides the best quality -- between 8Kbs (kilobits per second) and 16Kbs.

You can connect your MP3 player (like WinAmp) directly to the server at http://168.166.12.80:8000 for the House or http://168.166.12.81:8000 for the Senate.

Because there is no file extension for the streaming audio location, it is not possible to put a direct link into a web page. A browser would not know what to do with the stream. Instead, a link to an intermediary "play-list" file is used (HOUSE.PLS and SENATE.PLS) that contains almost nothing more than the URL of the audio stream. The only purpose is to have a special file extension that your browser understands is an MP3 stream that requires loading an MP3 player.

If you have installed your MP3 player correctly, your browser knows to use your MP3 player for any files with the .PLS extension. The MP3 player, like WinAmp, will open up the file, extract the IP address and port and make the streaming-audio connection.

All of the MP3 encoding and server software we are using is free. And, we've found, is fairly easy to set up. In fact, if you would like, you can take an audio stream from our House or Senate session and use it as the source for your own audio server.

If you would like to set up your own audio server, check out:

• Icecast which is the MP3 server we are using. It is an open source code project, which means that not only is the software free, but that the source code is available.
• Shoutcast which is another free MP3 server. As we continue our efforts with MP3, we may try the Shoutcast server. It was pretty impressive in our initial review. It is developed by the same group that develops WinAmp.
• WinAmp which serves both an MP3 player and the encoder for our MP3 audio -- the program that takes an analog audio source and converts it to a stream of MP3 digital audio. If you want to redistribute our House and Senate audio streams, you won't need WinAmp. Icecast alone will do the job for you.

Click here to return to the links for live audio from the legislature.