Re: bridging ASL, DMR and DSTAR


Ken KE2N
 

If you could run G722 at 16 kHz sampling within ASL that would be great.  But I imagine the 8 ks/sec rate is pretty hard-coded into asterisk and not easily changed.  Basically the issue is that the digital modes use vocoders and the analog side uses codecs.  The 8 kHz codecs were never intended to reproduce anything above 3.4 KHz.  If you pipe your digital radio to spectrum lab, or similar, you may be  surprised how much “stuff” there is up around 3.5 kHz on some signals …  it is better to chop that stuff off rather than generate a whole bunch of IMD with it.

 

 

Ken

 

 

 

From: main@DVSwitch.groups.io [mailto:main@DVSwitch.groups.io] On Behalf Of Steve KC1AWV
Sent: Wednesday, October 02, 2019 11:40 AM
To: main@dvswitch.groups.io
Subject: Re: [DVSwitch] bridging ASL, DMR and DSTAR

 

I see what you're getting at, Ken. I wonder if anyone has tried G722 on ASL? I think I have a desk phone that supports it, maybe I can try it out and see what happens.

 

 

On Wed, Oct 2, 2019 at 11:09 AM Ken KE2N via Groups.Io <ke2n=cs.com@groups.io> wrote:

going the other way (DMR/C4FM-> Analog) could use help too.  It seems the vocoders are quite capable of making a lot of sound energy in the 3-4 kHz range.  It's what gives those digital modes a characteristic "sharp" sound.  Unfortunately, on the ASL side, things are affected by the 8 ks/sec rate.  Although it is theoretically possible to reproduce 3.99 kHz sound with this sampling rate, audio gets more and more distorted as you go above 3 kHz.  It would be a big improvement if the digital stream were filtered through a steep low pass filter - with a shoulder just above 3 kHz - before being passed to the analog side of things,

Ken
KE2N



--

Steve Miller

KC1AWV

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