Sorry, forgot to answer this e-mail.
On Wednesday 25 October 2006 22:41, Ken Walker wrote:
> Just an update on this issue. I finally got some time to look at this
> again and found out the tones weren't be accepted because they were falling
> outside the MIN_TWIST limit using discriminator audio with deemphasis
> You had this set at -8, and some of my tones were coming in at up to
> -13. I readjusted to -15 and all decode fine now.
Thanks for the feed back. I have to check what the deemphasis filter is
actually doing. It doesn't seem to be completely ok.
73 de SM0SVX / Tobias
> Ken - KC9GKA
> Quoting Tobias Blomberg <sm0svx@...>:
> > On Monday 14 August 2006 19:57, Ken Walker wrote:
> > > Hello list,
> > >
> > > I have a new SVXLINK setup I just brought up. It is having
> > > problems decoding DTMF tones. When I run Dtmf_Plot I see an acceptable
> > > level for the tones (about 92%) and every tone is decoded properly with
> > > each key press. However, when svxlink itself is running, I only get the
> > > 1,4,5,7,8,0,* & # keys to decode.
> > >
> > > I am running this setup using discriminator audio into the sound
> > > card and have demphasis enabled in the config file. Is it possible the
> > > demphasis routine is mucking up the decoding of the tones? Does the
> > > dtmf_plot program look at and honor that config variable?
> > Dtmf_plot is not reading the configuration file at all. It was not
> > supposed to
> > be released at all. It was a tool I used during development. However, it
> > turned out to be quite useful after all so I released it. I have thought
> > of developing a new application to help adjusting audio settings. The
> > need for such an application have increased after adding the audio
> > processing (like deemphasis) to SvxLink.
> > The deemphasis certainly is your problem. You can verify this by
> > temporarily turning it off in the configuration file. All audio
> > processing code is very experimental and will probably have some
> > unexpected effects.
> > Please try to adjust the input gain up or down (most likely down) to get
> > better DTMF decoding. I'm afraid you have limited use for dtmf_plot when
> > using the deemphasis filter.
> > I usually adjust the input gain with open squelch so that the noise ends
> > up peaking just above 90% on the peak meter in dtmf_plot. The DTMF tones
> > peak a lot lower at maybe 50-60%. This could be a good adjustment to
> > start with. If you set the gain to high you risk having the signal
> > distorted even before SvxLink start to process the audio. This is not a
> > good point to start at. I'm planning to add an AGC at the front of the
> > audio processing chain and maybe an adjustable gain stage at the end of
> > the chain. These tools can be used to get the right audio levels in the
> > end instead of overdriving the sound card input.
> > If you feel like experimenting a bit, find the file
> > svxlink/rx/LocalRx.cpp. In
> > there, find the line "deemph_filt->setOutputGain(4);" and try to adjust
> > the gain value up or down to make it work. Recompile it all and try it.
> > Do this after adjusting the audio level as described above.
> > Please report to the list what you did to make it work if you get it to
> > work.
> > 73 de SM0SVX / Tobias
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