[rollei_list] Bitrate
- From: Jim Brick <jim@xxxxxxxxx>
- To: rollei_list@xxxxxxxxxxxxx
- Date: Sun, 01 Jan 2006 13:49:23 -0800
At 12:34 PM 1/1/2006, Jerry Lehrer wrote:
What is a "bitrate"?
Radio signals are analog signals. Voltage swings. In order to put
radio over the Internet, or on your hard disk, a CD, whatever, the
analog voltage swings have to be digitized.
An A/D converter (analog-to-digital converter) is used. As the
voltage is input to the A/D, it outputs a binary number representing
the voltage at that particular instant. In order to digitize a radio
broadcast, a very fast A/D must be used so the binary number stream
coming out of the A/D is coming at a high speed, a high bit rate.
When you put this binary number stream onto the Internet, there has
to be bandwidth enough to carry the high bit rate. It is actually
multiplexed onto the Internet in packets. If more and more bit
streams are multiplexed onto the Internet along with the original
radio broadcast (in the same packet), this uses up some of the
bandwidth so the recipient of the radio broadcast cannot get the
digital bits fast enough to be heard as if you were listening to it
via an analog radio. The A/D conversion bit data stream cannot get
100% through, so the reception on the other end of the Internet (your
computer, where the digital bit data stream goes through a D/A
converter to convert it back to an analog voltage, which drives your
speakers or headphones) is not as clear and whole as the original
analog radio signal. It can have hiccups, missing syllables, and
other annoying glitches.
:-)
Jim
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