[arm-allstar] New Channel Driver Code in Debelopment

[David McGough]

What CODECs are being used at 16KHz in SVXLink??  Opus?


On Fri, 29 Apr 2022, "Patrick Perdue via ARM-allstar" wrote:

> SVXLink operates at 16 kHz.
> 
> Yes, I can definitely hear a clear difference, even on FM, at least with 
> some radios. Yaesu comes to mind. Those radios tend to cut off closer to 
> 5k than 4, so listening to a Yaesu over SVXLink sounds more like 
> simplex. Granted, I've only actually heard this in recordings of SVXLink 
> demonstrations.
> 
> With the pervasiveness of Baofengs though, I don't know how many would 
> actually notice if the sampling rate were increased 2x, and the filters 
> adjusted accordingly. Even most analog repeaters I've come across are 
> *at least* as limited as 4 kHz, and usually more. I've heard examples of 
> better, but it's pretty rare now.
> 
> I say all this as someone who is in favor of using 16 kHz audio as a 
> backbone for FM via VoIP, at least in theory. Most probably wouldn't 
> notice or care, and it would make the most difference when linking 
> well-tuned repeaters together, which is exactly how SVXLink is being 
> used, though I don't think it's very popular in the U.S. for that 
> application.
> 
> HamVoIP does support G.722, but I think this is mostly for compatibility 
> reasons, and won't actually do anything to increase the frequency 
> response when using radios due to a well-done implementation of low 
> pass/anti-aliasing on the simpleusb driver, among other things. Having 
> used ASL, which doesn't have as good implementation in comparison, I 
> definitely do appreciate that. Maybe if everyone is on a VoIP phone set 
> to G.722, you'd notice.
> 
> 
> On 4/29/2022 5:37 PM, "M Lech via ARM-allstar" wrote:
> > While we're at it, can we implement 16KHz sampling instead of the crummy
> > 8KHz sampling ? I'd think I'd died & went to heaven to have the audio
> > bandwidth matching our RF links. For me this is huge. The hardware has no
> > problem doing it, so why don't we? Thanks in advance!
> >
> > 73,
> > Matt W6XC
> >
> > On Fri, Apr 29, 2022 at 9:27 AM "Dave Petrie via ARM-allstar" <
> > arm-allstar at hamvoip.org> wrote:
> >
> >> Hi David, just curious if you made any progress with the new channel driver
> >> code in development so that chan_simpleusb can send and receive CTCSS like
> >> usbradio does. Here is what I found that led me to ask the question.
> >>
> >> On 9/5/21 11:41 PM, David McGough wrote:
> >>
> >> Hi Jim,
> >>
> >> CTCSS generation isn't currently in the chan_simpleusb code. However, it
> >> is in new channel driver code in development.
> >>
> >> All the original usbradio related code and features are in HamVoIP. So,
> >> that should work, if you can tolerate the sporadically glitchy sounding
> >> audio.
> >>
> >> How quickly do you need this?  I can probably get you info on the new
> >> channel driver in a few days.
> >>
> >>
> >> 73, David KB4FXC
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> >>
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> >>
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