On 22/07/2015 20:33, Richard Shaw wrote:
Hi Richard,
Wed, Jul 22, 2015 at 2:14 PM, Bill Somerville <[email protected]
<mailto:[email protected]>> wrote:
On 22/07/2015 18:45, Richard Shaw wrote:
Hi Richard,
I'm not sure who else has battled this but Qt in their infinite
wisdom decided they need a random name for the audio connection
to PulseAudio which means it will NEVER remember the volume level
you set.
What's wrong with setting the levels in WSJT-X, those settings are
saved between sessions?
I have to cut it WAY down and I haven't done any actual analysis, but
the instructions indicate that that's not a good thing. Why amp up
your audio in software just to knock it back down in software? It
can't possibly help the audio quality.
You are right in principle but I would expect the default level to be
0dB i.e. what comes out of the A/D converter so doing all digital
attenuation in WSJT-X is optimal since it limits any accumulated
quantization error. The same would apply if the WSJT-X level were left
at 0dB (the middle I believe) and all digital adjustment were done in
the pulseaudio digital domain.
The best solution is to set the analog level at he rig to a best
approximation and only do fine adjustments per band or to compensate for
AGC variations in the Rx.
And either way, it's still just obnoxious on the Qt side. I wonder how
many presets PulseAudio has stored for device names it will never see
again?
Agreed that it would be nice to have a way of setting the stream name on
Linux, but there is an alternative where, like we do with Tx, the stream
level can be directly adjusted from the application using the stream
(http://doc.qt.io/qt-5/qaudioinput.html#setVolume). This allows the
application to store the level itself. Currently WSJT-X doesn't use
this, instead it has its own gain/attenuation stage further downstream
in the DSP chain. I believe the built in gain stage is both historical
from before we switched to Qt audio and also to provide gain as well as
attenuation (gain is not available on some platforms).
I expect the availability of adjustment of the stream level via the Qt
API is the reason why our request to control the stream name has been
ignored by the Qt developers.
Thanks,
Richard
73
Bill
G4WJS.
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