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New Member

Which Codec?

I am running radio remote controls over E&M ports and through frame relay. I need to send in-band signalling tones to make this work. Here's what happens when the push-to-talk button is pressed:

The remote control sends

1) 2175 Hz at +10 dBm for 125 msec, then

2) 1950 Hz at 0 dBm for 40 msec, then

3) 2175 Hz at -20 dBm until the push-to-talk button is released.

Which audio codec is best suited for this environment? Of course, I would like to use the lowest bit rate with the best results.

3 REPLIES
Silver

Re: Which Codec?

We have had several customers do this to interface VHF radio repeaters. It works using G729 codecs - you need to set up the QOS on the frame relay side of things to ensure the audio quality is maintained when the link is congested.1 call will take up 24K without CRTP. The compression will add a litlle distortion to the signal, so the radios may need to be tolerant of this. If the G729 doesn't work, you can try some of the higher bit rate codecs, such as 16K or 32K.

New Member

Re: Which Codec?

Thank you. Good to know that G729 will work.

Now the question is:

Which codec is best suited to passing constant tones without distortion and tones that must be recognized and passed in quick succession?

Anyone know enough about codecs to venture a guess?

Cisco Employee

Re: Which Codec?

To conserve BW and have good quality the 729 codec is the best. If you are concerned about BW then the 711 codec would be the way to go. I am attaching a URL that goes over the testing and the scores received with each codec(MOS).

http://www.cisco.com/warp/public/788/voip/codec_complexity.html

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