Low cost remote stereo feed to FM station
Mon May 7 11:51:04 EDT 2007
At WBRS lately we've had a Barix Instreamer serve as the webcast encoder
source - encoding a feed off the mix board (and through an EQ & Alesis
compressor) and sending it off to Live365.com to be "served" out to the
public internet. Eventually a regular computer will resume that
encoder function and the Instreamer will be paired with an Exstreamer to
serve as a backup STL across the campus LAN.
The Barix boxes are remarkably stable, both in normal operation (there's
no OS to crash like Windows) and in terms of getting audio reliably
across the internet. I've see favorable reviews from other public radio
stations using them for similar purposes, too. They're also fairly
cheap - an In/Ex-streamer pair is about $600-$700. You can find 'em
through a Google Search.
The Barix boxes use VBR MP3's, and for a stereo feed "broadcast quality"
demands about 112 to 128kbps of bandwidth. Mono feed requires half as
much bandwidth. All MP3's will need that.
Other codecs, such as Real, AAC or Windows Media Player can get
"broadcast quality" with somewhat less bits; I've seen the AAC+ codec
deliver impressive stereo sound at only 40kbps. But the piper must
always be paid; using that few bits can get you into trouble if the
wrong audio source material is used. For example, many low-bitrate
codecs sound fine with music because of the complexity of the source
material (acoustic masking) but they suddenly sound pretty lame on
voice-only. Plus, if your radio station is broadcasting in HD Radio, or
transmits a webcast, you run into "cascading algorithms" which means an
already-heavily-compressed audio feed is getting compressed again. That
can lead to crummy audio.
Still, any halfway decent DSL line should be able to handle 112-128kbps.
Just make sure nobody else is using the internet connection during
live broadcasts! :-)
I'd be hesitant to recommend a "normal" POTS solution because finding a
clean enough POTS line can be a real bear. A POTS solution that works
over CSD is also a bad long-term investment as more and more cell
providers migrate away from a CSD platform. However, the two main POTS
codec providers - Comrex and Tieline - are aware of this and have
started making "POTS" Codecs that are really IP Codecs, and they work
remarkably well. About two months ago I demoed a Tieline Commander G3
with a Sprint EVDO wireless PCMCIA card plugged into Linksys
PCMCIA-to-RJ45 Gateway and it worked amazingly well. I've seen demos
of the Comrex Access device and it also works quite well.
Even over the public internet, these things tend to be remarkably
stable...even over limited bandwidth like a cellphone (which frequently
is a lot less than DSL)...but yes, sooner or later you probably will get
"bitten" by a downed internet connection or something like that.
If you want more five-nines reliability you probably want to go with
ISDN or satellite. The latter has long-term prospects but is
prohibitively expensive. The former costs about as much as POTS Codecs
do (a new Telos Zephyr ISDN is about $3500 a pop, you'll need
two...although they can be had on eBay sometimes for around $1500 each)
although you'll pay per-minute line fees (similar to POTS long distance)
for the ISDN calls. The rub is that ISDN is slowly being phased out as
a service that Verizon and other CLECs are providing...so getting ISDN
service can be a real PitA in your area, and you'll want to stay on top
of it. The good news is that it's a SLOW phase out; ISDN will be
around in one form or another for another 10 years at least (I'd guess).
Boston, MA 02446-2204
I have been trying to figure out what a low-cost solution to sending
high fidelity stereo "sans" POTS hum and noise to the broadcast station
might be. So far, all I can come up with is approaching the station
management with the idea of the church sending left and right data
streams to them via the internet. But I'm not sure whether our current
DSL bandwidth is sufficient to do that reliably. Nor do I know how much
of a selling job I might have to do at the station end of things.
More information about the Boston-Radio-Interest