Anyone using FR as a phone?
openmoko at mazikeen.demon.co.uk
Tue Jul 22 01:53:08 CEST 2008
On Monday 21 July 2008, Timo Jyrinki wrote:
> 2008/7/21 Al Johnson <openmoko at mazikeen.demon.co.uk>:
> > Assuming there is sufficient difference in level between voice level and
> > the level from the earpiece it should be possible to set the noise gate
> > so that it only triggers when you are actually speaking, stopping the
> > echo. The compressor should even out the variations in level.
> So is basically everyone who is being called with a Neo Freerunner
> having at least a little echo of her own voice? At some point I had
> often the problem that the receiver heard everything she said very
> aloud about 1s later, now in at least my own tests it's merely quite
> quiet repetition that doesn't always even occur (gets cut off by
> something, eg. a noise filter). I used gsmhandset.state from here:
> and also stored it at /etc/asound.state.
That depends ;-) One of the things that contributes to the variety of reports
is that you never know what the telcos are doing with the signal between you
and the other end. Changes in gain, dynamic range alteration and echo
cancellation are all possible, and may not be consistent from call to call.
Another problem is that it's rather subjective. I don't know how much sample
to sample variation there may be.
I think there has been more than one mixer scenario since I got the phone, but
with the ones I've actually looked at the noise gate is not enabled. It seems
like in the gsmhandset.state the echo has been avoided by setting the mic
gain and earpiece volume low, but people complain that they can hardly hear
you. A bit of extra mic gain seems to help here without adding too much echo.
The gsmspeakerout state has more mic gain and playback through the speaker
now. I think it used to play through the earpiece, but in either case it
gives some echo, at least when I've tried it.
I got as far as checking that the noise gate does operate, but there are a lot
of adjustments available in this area. Routing to the ADC/DAC should make
measurement of the echo possible. Someone mentioned xoscope which I'll have
to look at too.
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