BatPhone voice quality problem identified
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Paul Gardner-Stephen
Jul 21, 2010, 8:47:45 AM7/21/10
to village-telco-dev
As some of you know, one minor problem we had at the Arkaroola field
test of the BatPhones, was that the voice quality was terrible
whenever we tried to film them making calls.
It turns out the problem due to feedback when the phone is on speaker
mode, partly because their is no echo cancellation.
As a result the echo overwhelms the voice signal, and the result
sounds like Darth Vader with whooping caugh.
Local tests here since (and as I now recall before) confirmed that the
quality is fine when in normal phone-to-ear mode.
So the good news is that it was nothing to do with the mesh or wifi.
The bad news is that we will have to think about how to get echo
cancelling onboard.
David: What do you use for echo cancellation in the Mesh Potatoes?
Paul.
test of the BatPhones, was that the voice quality was terrible
whenever we tried to film them making calls.
It turns out the problem due to feedback when the phone is on speaker
mode, partly because their is no echo cancellation.
As a result the echo overwhelms the voice signal, and the result
sounds like Darth Vader with whooping caugh.
Local tests here since (and as I now recall before) confirmed that the
quality is fine when in normal phone-to-ear mode.
So the good news is that it was nothing to do with the mesh or wifi.
The bad news is that we will have to think about how to get echo
cancelling onboard.
David: What do you use for echo cancellation in the Mesh Potatoes?
Paul.
Andrea Carradore
Jul 21, 2010, 9:06:20 AM7/21/10
to village-...@googlegroups.com
I can confirm this problem shall not be due to wifi nor whatever technology in use since I experienced it even in a real gsm network when I was testing wb amr . I was going crazy because simulating tests were not revealing any problem in voice frames transmission, while a real phone call risulted hard to decode..
The trick was that in speaker mode the phone filter is practically cut out, so that the voice is decoded as noise.
I think the problem you have should belong to the same family :-)
Andrea
2010/7/21 Paul Gardner-Stephen <paul.gardn...@gmail.com>
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Paul Gardner-Stephen
Jul 21, 2010, 1:39:15 PM7/21/10
to village-telco-dev
Hi Andrea,
Thank you for that vote of confidence -- it is reassuring.
Now to figure out how to get some echo cancelling, as it is clear that
echo is present even when using the phone normally.
Paul.
On Jul 21, 10:06 pm, Andrea Carradore <andrea.carrad...@gmail.com>
wrote:
> > .
Thank you for that vote of confidence -- it is reassuring.
Now to figure out how to get some echo cancelling, as it is clear that
echo is present even when using the phone normally.
Paul.
On Jul 21, 10:06 pm, Andrea Carradore <andrea.carrad...@gmail.com>
wrote:
> I can confirm this problem shall not be due to wifi nor whatever technology
> in use since I experienced it even in a real gsm network when I was testing
> wb amr . I was going crazy because simulating tests were not revealing any
> problem in voice frames transmission, while a real phone call risulted hard
> to decode..
>
> The trick was that in speaker mode the phone filter is practically cut
> out, so that the voice is decoded as noise.
>
> I think the problem you have should belong to the same family :-)
>
> Andrea
>
> 2010/7/21 Paul Gardner-Stephen <paul.gardner.step...@gmail.com>
> in use since I experienced it even in a real gsm network when I was testing
> wb amr . I was going crazy because simulating tests were not revealing any
> problem in voice frames transmission, while a real phone call risulted hard
> to decode..
>
> The trick was that in speaker mode the phone filter is practically cut
> out, so that the voice is decoded as noise.
>
> I think the problem you have should belong to the same family :-)
>
> Andrea
>
>
>
>
> > As some of you know, one minor problem we had at the Arkaroola field
> > test of the BatPhones, was that the voice quality was terrible
> > whenever we tried to film them making calls.
>
> > It turns out the problem due to feedback when the phone is on speaker
> > mode, partly because their is no echo cancellation.
> > As a result the echo overwhelms the voice signal, and the result
> > sounds like Darth Vader with whooping caugh.
>
> > Local tests here since (and as I now recall before) confirmed that the
> > quality is fine when in normal phone-to-ear mode.
>
> > So the good news is that it was nothing to do with the mesh or wifi.
>
> > The bad news is that we will have to think about how to get echo
> > cancelling onboard.
>
> > David: What do you use for echo cancellation in the Mesh Potatoes?
>
> > Paul.
>
> > --
> > You received this message because you are subscribed to the Google Groups
> > "village-telco-dev" group.
> > To post to this group, send email to village-...@googlegroups.com.
> > To unsubscribe from this group, send email to
> > village-telco-...@googlegroups.com<village-telco-dev%2Bunsubscr i...@googlegroups.com>
>
>
> > As some of you know, one minor problem we had at the Arkaroola field
> > test of the BatPhones, was that the voice quality was terrible
> > whenever we tried to film them making calls.
>
> > It turns out the problem due to feedback when the phone is on speaker
> > mode, partly because their is no echo cancellation.
> > As a result the echo overwhelms the voice signal, and the result
> > sounds like Darth Vader with whooping caugh.
>
> > Local tests here since (and as I now recall before) confirmed that the
> > quality is fine when in normal phone-to-ear mode.
>
> > So the good news is that it was nothing to do with the mesh or wifi.
>
> > The bad news is that we will have to think about how to get echo
> > cancelling onboard.
>
> > David: What do you use for echo cancellation in the Mesh Potatoes?
>
> > Paul.
>
> > --
> > You received this message because you are subscribed to the Google Groups
> > "village-telco-dev" group.
> > To post to this group, send email to village-...@googlegroups.com.
> > To unsubscribe from this group, send email to
> > .
David Rowe
Jul 21, 2010, 5:24:05 PM7/21/10
to village-...@googlegroups.com
Hi Paul,
On the MP we use Oslec for (Line Echo Cancellation) on the FXS port:
http://www.rowetel.com/ucasterisk/oslec.html
For speakerphone mode (and even handset mode if there is significant
acoustic coupling) you need an Acoustic Echo Canceller (AEC), a related
but different beast. You also need enough MIPs to run it on host CPU
(about 20 MIPs for Oslec, possibly more for an AEC).
There is an open source AEC as part of the Speex codec.
Is there echo in a normal GSM call on the Android handset? You should
get the same speech quality for a SIP call.
Cheers,
David
Paul Gardner-Stephen
Jul 21, 2010, 8:06:01 PM7/21/10
to village-telco-dev
Hi David,
On Jul 22, 6:24 am, David Rowe <da...@rowetel.com> wrote:
> Hi Paul,
>
> On the MP we use Oslec for (Line Echo Cancellation) on the FXS port:
>
> http://www.rowetel.com/ucasterisk/oslec.html
>
> For speakerphone mode (and even handset mode if there is significant
> acoustic coupling) you need an Acoustic Echo Canceller (AEC), a related
> but different beast. You also need enough MIPs to run it on host CPU
> (about 20 MIPs for Oslec, possibly more for an AEC).
>
> There is an open source AEC as part of the Speex codec.
Thank you -- that makes it very clear that I can focus on getting the
codecs right.
> Is there echo in a normal GSM call on the Android handset? You should
> get the same speech quality for a SIP call.
To be honest, I don't know, I have never actually put a valid SIM card
in one of these phones.
But I will try it as soon as I get a chance.
I would also like to try some maximum range trials when I get the
chance.
Paul.
On Jul 22, 6:24 am, David Rowe <da...@rowetel.com> wrote:
> Hi Paul,
>
> On the MP we use Oslec for (Line Echo Cancellation) on the FXS port:
>
> http://www.rowetel.com/ucasterisk/oslec.html
>
> For speakerphone mode (and even handset mode if there is significant
> acoustic coupling) you need an Acoustic Echo Canceller (AEC), a related
> but different beast. You also need enough MIPs to run it on host CPU
> (about 20 MIPs for Oslec, possibly more for an AEC).
>
> There is an open source AEC as part of the Speex codec.
codecs right.
> Is there echo in a normal GSM call on the Android handset? You should
> get the same speech quality for a SIP call.
in one of these phones.
But I will try it as soon as I get a chance.
I would also like to try some maximum range trials when I get the
chance.
Paul.
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