Voic e over IP remotes

[grampagonzo]

I'm curious about the experiences you other radio techies have had with voice over IP remotes. Our station has been using a Tieline TLF300 and TLR30o0B in combo. We went wireless IP on a football game last week.. with a Verizon air card and a Kyocera internet bridge connected to the field unit. Good sound and stable connection at a 16.8 baud rate. I'm curious what other experiences people have had, and the pitfalls we need to watch out for

 

[vetguy]

We have been using the Comrex access system for several months now. Overall it work beautifully. Only time it would not work was when we were set up directly under a building that had cell antennas for almost every carrier out there (But Verizon) on top of the building. Blanketing by all of the other transmitters kept our Verizon card from working. Not sure but I believe the closest Verizon tower was several blocks away. Aside from that one issue, the staff takes it everywhere. Plug and play.

 

[OttoM]

There's been a lot of wireless remote gear discussions on the "other" Engineering board. Go to the search box on this page and type "wireless remotes" (without the quotes) and you'll find the other threads.

 

[LA_Guy]

Several Barix Customers are running Annuncicoms with special full duplex firmware over 3g wireless links to their stations. They get a low latency bi-directional audio path that way. They are running the ulaw codec (which sounds similar to G.722) for voice. This codec is the trick for the low latency they get.

 

[ChiefOperator]

VOIP sounds like a great option. The Barix sounds like a great, stable connection. Is anyone using Audio Compass VOIP software? I believe it uses the Speex codec, among others. I wonder how it works with EVDO Rev. A

Looks like a nice product, but I haven't heard too many experiences with it.

 

[RolfTaylor]

This thread has gotten rather confused....

1) VoIP generally implied voice band. Tieline, Comrex, APT, and Barix are better described as Audio over IP to distinguish that they are intended for voice-with-backround-noise, and music, as well as voice.

2) The mU Law codec (part of ITU G.711) is familiar to all as it is the codec used for voice telephone calls in the US. It is limited to 300-3.4 kHz and using a whopping 64 kbps to do so. It is most certainly not similar to G.722 in quality - G.722 can achieve 7 to 7.5 kHz bandwidth at 56 kbps! It is low delay.

3) Delay is more critical when using IP since packetization and routing ad substantial delay

For more on this and other factors involved with Audio over IP check out our the new third edition of our Audio over IP guide here (or contact me off line and I can send you the printed version): http://www.aptx.com/Admin/Editor/Assets/PDF/IP Audio Networking.pdf

4) The worse the network, the more buffering will be required. This delay becomes a bigger issue. Enhanced apt-X, included in all of our codecs, and licensed to many codec manufacturers worldwide, has an encode/decode delay of less than 3 msec. It the same 64 k bits per second that mU law uses for mono phone quality audio, it can give you two channels of 20-3.5 kHz pro-grade (low noise and distortion) audio.

I hope this helps untangle this thread.

Rolf Taylor
Applications/Support Engineer

APT North America

800-955-APTX (2789)

 

[ChiefOperator]

Rolf-

Thanks for clearing that up and thanks for the booklet. I read through the booklet and it certainly clarified many concepts. I too have been guilty of interchanging the AoIP and VoIP terms.

It seems that VoIP could certainly be used on voice remotes, such as the local high school football game. While the AoIP gear, such as APT, Comrex, etc., is nice and the first choice for those stations that can afford it, many small stations can't spend that kind of $$. For those stations, VoIP devices and software (such as Audio Compass) could be a solution. Agree, Disagree??

 

[gunterm]

VOIP sounds like a great option. The Barix sounds like a great, stable connection. Is anyone using Audio Compass VOIP software? I believe it uses the Speex codec, among others. I wonder how it works with EVDO Rev. A

Looks like a nice product, but I haven't heard too many experiences with it.

I haven't used it over the air, but my testing of audio compass with speex at 44.1 using an AT&T 3G card worked very well. I have access to Evdo Rev 0 so I'll try that with speex also, the bitrate is low enough to where it should work fine.

 

[ChiefOperator]

Re: Voice over IP remotes

Thanks...

The site says you can get a "ISDN quality" audio connection. Would you agree? Also, what is the longest you were up with the 3G connection? I'm wondering whether that set up would carry a 3 hour sports remote..

 

[gunterm]

Re: Voice over IP remotes

Thanks...

The site says you can get a "ISDN quality" audio connection. Would you agree? Also, what is the longest you were up with the 3G connection? I'm wondering whether that set up would carry a 3 hour sports remote..

I think ISDN's bandwidth for audio is actually half of 44.1 khz, however speex has its limitations. You cannot send anything other than speech or it will be a little garbled. I had the 3G active for about an hour with the connection to the other end, and after that I was surfing for another hour.

I got some e-mail from the author of the program and he says more codecs are coming soon, the biggest improvement to the software would be MP3 so that general purpose audio could be sent.