Streaming media
Last updated: May 24, 2007.
A decade or two ago, the telephone wire heading into your home was a
quaint way to chat with your family and friends when you couldn't speak
to them in person. The basic idea hadn't changed much since the 1870s,
when Alexander Graham Bell (1847-1922) and others pioneered telephone
technology. But in the 21st century, people have started to see
telephone lines a different way: now they're
Internet broadband connections, piping
music downloads, YouTube videos, news, and information—as well as
telephone calls—into our homes 24 hours a day. "Streaming media" (a way
of playing files as they download) has been a central part of this
information revolution. What is it, exactly, and how does it work?
Photo: Yahoo! Music is a typical website that
brings music into your home using streaming media.
Information rich
If a picture is a worth a thousand words, a moving picture is worth
a million. But how do you send all that information down a telephone?
The trouble is that a couple of copper wires—the basic technology
behind our home phone lines—cannot, ordinarily carry information
quickly enough to bring things like radio and
TV into our homes. If
you've ever watched a fax machine chugging along, sending or receiving
a printed document at a grindingly slow speed, you'll know just how
slow telephone lines can be at carrying anything other than a person's
voice (the only job they were ever designed to do).
In the days when most people had dialup
Internet connections (where you make a connection to your Internet
Service Provider through a normal telephone call), slow speeds were a
major limitation on what could be do online. If you wanted to listen to
an MP3 music track
(typically about 5 megabytes in size), you could spent half an hour
waiting for the entire file to download onto your hard drive, then open
it up and play it back. Video files (more likely to be 50 megabytes)
would take several hours to download this way, so they were not
generally available on the Net. In those days, it was impossible to
listen to a music or movie file of any size without a long and tedious
wait.
Less is more
Photo: RealPlayer: the program that
kick-started the streaming media revolution. The status bar at the
bottom shows the radio station is being played at 44.1 Kbps (over
44,000 binary digits per second), which is a rate even dialup
connections can handle.
In the mid-1990s, in the early days of the Web, Rob Glaser and his
Real company (originally called Progessive Networks) pioneered
streaming technology: a way of getting "more" out of a dialup or slow
broadband connection. The basic
idea is simple. Suppose you want to watch a large video file on your
PC. You install a media-playing
program on your computer that plays the
file while it downloads. So it downloads maybe the first 10 seconds of
the file, stores or "buffers" it, then immediately starts to play it.
As the program plays the first part of the file, it's also downloading
the next 10 seconds ready for when you come to that bit. The program
never actually stores more than a little bit of the entire file. Once
it's played part of the file, it deletes it.
Most Internet radio stations use this kind of streaming-media
technology, downloading and playing simultaneously with a program like
RealPlayer, Apple's QuickTime, or the Microsoft Windows Media Player.
As Internet connections have become faster, and more people have
broadband, it's become possible to download videos this way too.
Popular websites like Google's YouTube also work by streaming.
Underneath the video window, you can usually see two progress bars: one
shows you how quickly the file is downloading and the other how quickly
it is playing. The trick with streaming media is for the media player
to download the file more quickly than it plays it. If your connection
is slow or poor, there will be frequent pauses, because the file is
being played more quickly than it's downloading.
Where next?
Photo: Apple's QuickTime offers a choice of
streaming music and movies.
Streaming media—bringing music and videos on demand—may seem
advanced compared to the kind of technology people had a few years ago,
but it's still quite primitive. The audio and video information you
download often has to be compressed (reduced in quality to make smaller
files) so it downloads in a reasonable amount of time. You'll have
noticed that streaming videos are still quite small and "pixelated"
(full of obvious square blocks) when they play on something like
YouTube. That's because even today's best broadband connections are not
fast enough to download the huge amount of information in a good
quality, fullscreen DVD picture. In a few years (or decades?), when
broadband connections are many times faster, it will be possible to
stream DVD quality videos over the Net. Then the age of
information-on-demand really will have arrived!
