[op25-dev] Why can't I hear fire tones?

gnorbury@bondcar.com [op25-dev] op25-dev at yahoogroups.com
Wed Jun 20 22:58:54 UTC 2018


The vocoder used in op25 is open source so anyone can modify it.  Trouble is, unless you are well versed in DSP techniques and in particular the IMBE/AMBE codec the learning curve is going to be a big mountain to climb.
 

 Right now ambe synthesized tones are not handled.  See ./lib/ambe.c and more specifically  mbe_dequantizeAmbeParms()

 

 Some jurisdictions pass tones as audio on their dispatch channel.  Our local dispatch center does this, but only basic "alert" tones, not pagers.  These audio tones are playable by op25 because they are encoded as voice, whereas pager alerts would have to be encoded as 'tones' in order to ensure accurate decoding by the receiving device. 
 

 Graham

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