Hi Jim,
in my case I was referring to the digital radio here in the UK. When
the system first came on line - quite a few years ago - the quality
was quite high on the few channels that were broadcast. Certainly
much better than the internet "radio" channels. I have 2 tuners for
DAB, one a permanent installation and the other a portable. As
digital radio has got more popular - the BBC has had a big
advertising push - more channels have been put on the same carrier
and the broadcast bitrate per channel has gone down. At the beginning
digital radio was excellent, hiss free and with good sound quality.
Many channels are now broadcast at lower quality, which is OK on the
portable or car radio, but disappointing on a good hifi.
Nevertheless even the worst of them are broadcast at higher bitrates
than the majority of internet radio which are also in Real, Windows
media etc. formats.
Frank
On 1 Jan, 2006, at 21:49, Jim Brick wrote:
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 --- Rollei List
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