Tuesday, November 14, 2006

Streaming Audio

Cork Factory. The Strip, Pittsburgh, PA. 2005,
digitally scanned and inverted pinhole paper negative.
© 2005 by Allen C. Benson.


Today I loaded Eating Quail's Egg as a streaming audio file. For those interested in learning how this is done, read on. I loaded the original archival file, which was stored in Windows PCM (.wav) format, into a sound editor called Cool Edit 2000. I used the sound editor to resave the file in RealMedia G2 (.rm) format. RealMedia files can be streamed over the Internet, i.e., you can listen to them as they download. Mp3 files, on the other hand, must be downloaded in their entirity before you can listen.

Yesterday I presented the audio clip Eating Quail's Egg in Mp3 format. The file size was 313KB. The RealMedia file is only 264KB in size. With voice-only recordings, the difference in audio quality isn't that noticable between an Mp3 file and the more highly-compressed RealMedia file. The original archival-quality file saved in .wav format was 3,437KB in size. As its name implies, archived files remain unchanged, uncompressed, and are stored for the longterm. You make copies and reformat the copies for various purposes, for example delivery over a network, or playable on CD-ROM, but you always leave the archival copy in its original state.

I use WestHost.com as a service provider for delivering streaming audio. The hyperlink above directs you to a plain ASCII text file, not the audio clip itself. When streaming audio, you rely on a protocol different from HTTP (HyperText Transfer Protocol) and the purpose of this text file is to help you bypass HTTP. In this example I used RTSP (Real Time Streaming Protocol), which enables you to control the streaming audio clip using, for example, play, stop, and pause commands.

The text file, named quailsegg.ram contains only one line of text, which reads
rtsp://www.star-host.com/realaudio/quailsegg.rm
This URL contained within the text file points to the RealMedia audio clip, which is stored in the same directory and named quailsegg.rm.

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