Re: [Asterisk-Users] more cpu intensive echo cancellers ?
Gerard Saraber
> Try MG2 with trunk and KB1 with 1.2. KB1 is supposed to be fairly
> reliable in 1.2, and MG2 in trunk has a good possibility of
> outperforming KB1 from 1.2.
>
> Matthew Fredrickson
Thanks! testing it now, on my test calls it appears to start out with
less echo then the Mark3 canceler, but it trains slower, seems like it
took a long time for the echo to completely disappear, the real test
will be seeing what the people at my company have to say.
Feb 9 14:47:51 [kernel] Zapata Telephony Interface Registered on major
196
Feb 9 14:47:51 [kernel] Zaptel Version: SVN-trunk-r934M Echo Canceller:
MG2
--
Thanks again,
Gerard Saraber
Network Admin, Rarcoa, Inc.
(630) 654-2580 x11
gsar...@rarcoa.com
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Clint Sharp
>Thanks! testing it now, on my test calls it appears to start out with
>less echo then the Mark3 canceler, but it trains slower, seems like it
>took a long time for the echo to completely disappear, the real test
>will be seeing what the people at my company have to say.
>
>Feb 9 14:47:51 [kernel] Zapata Telephony Interface Registered on major
>196
>Feb 9 14:47:51 [kernel] Zaptel Version: SVN-trunk-r934M Echo Canceller:
>MG2
>
>
>
I've had really good luck with the echocan preload patch that was posted
on the asterisk dev list a while back as well, and I've been
recommending it to people as well. This has really helped minimize the
echo problems to a minimal level, although I don't know about
recommending this system to our customers. I still think a lot of my
audio quality problems are being caused by my phones (not echo, but
clicks and pops and various overmodulation problems). We're getting
there, but I'm still nervous with trying to sell an * system to someone
who is used to the quality of a traditional PBX or key system.
Clint
Gerard Saraber
> Gerard Saraber wrote:
>
> >Thanks! testing it now, on my test calls it appears to start out with
> >less echo then the Mark3 canceler, but it trains slower, seems like it
> >took a long time for the echo to completely disappear, the real test
> >will be seeing what the people at my company have to say.
> >
> >Feb 9 14:47:51 [kernel] Zapata Telephony Interface Registered on major
> >196
> >Feb 9 14:47:51 [kernel] Zaptel Version: SVN-trunk-r934M Echo Canceller:
> >MG2
> >
> >
> >
> I've had really good luck with the echocan preload patch that was posted
> on the asterisk dev list a while back as well, and I've been
> recommending it to people as well. This has really helped minimize the
> echo problems to a minimal level, although I don't know about
> recommending this system to our customers. I still think a lot of my
> audio quality problems are being caused by my phones (not echo, but
> clicks and pops and various overmodulation problems). We're getting
> there, but I'm still nervous with trying to sell an * system to someone
> who is used to the quality of a traditional PBX or key system.
>
> Clint
Found it, going to go test it right now :) thanks!
So far reports have been positive on the echo, but its a slow day ;)
We're using cisco 7960 phones, they're pricy, but they work great and
sound good, if it wasn't for the echo issue, I would have been able to
roll the whole setup out already.
Actually that's not quite true, I still have to make the 7914 addon
module work with the 7960 phone, but that's not a show stopper.
Either way, so far big thumbs up for the MG2 echo can, and if any
developers read this, feel free to add a compile flag to make it more
cpu intensive ;) and do more canceling.
--
Regards,
Gerard Saraber
Network Admin, Rarcoa, Inc.
(630) 654-2580 x11
gsar...@rarcoa.com
_______________________________________________
Matthew Fredrickson
On Feb 10, 2006, at 1:21 PM, Gerard Saraber wrote:
>
> Found it, going to go test it right now :) thanks!
> So far reports have been positive on the echo, but its a slow day ;)
> We're using cisco 7960 phones, they're pricy, but they work great and
> sound good, if it wasn't for the echo issue, I would have been able to
> roll the whole setup out already.
> Actually that's not quite true, I still have to make the 7914 addon
> module work with the 7960 phone, but that's not a show stopper.
>
> Either way, so far big thumbs up for the MG2 echo can, and if any
> developers read this, feel free to add a compile flag to make it more
> cpu intensive ;) and do more canceling.
>
Does latest MG2 behave better than KB1 on your analog lines? I heard
in the past that in some cases (primarily with analog lines) that KB1
worked better. Also, have you tried the echotraining=800 (in
zapata.conf) tweak as well?
---
Matthew Fredrickson
Steve Underwood
>
> On Feb 10, 2006, at 1:21 PM, Gerard Saraber wrote:
>
>>
>> Found it, going to go test it right now :) thanks!
>> So far reports have been positive on the echo, but its a slow day ;)
>> We're using cisco 7960 phones, they're pricy, but they work great and
>> sound good, if it wasn't for the echo issue, I would have been able to
>> roll the whole setup out already.
>> Actually that's not quite true, I still have to make the 7914 addon
>> module work with the 7960 phone, but that's not a show stopper.
>>
>> Either way, so far big thumbs up for the MG2 echo can, and if any
>> developers read this, feel free to add a compile flag to make it more
>> cpu intensive ;) and do more canceling.
>>
>
> Does latest MG2 behave better than KB1 on your analog lines? I heard
> in the past that in some cases (primarily with analog lines) that KB1
> worked better. Also, have you tried the echotraining=800 (in
> zapata.conf) tweak as well?
A lot of the variability is probably due to thr lack of a DC blocker at
the front of the echo canceller. As far as I remember, none of the
cancellers in * has a DC blocker.
Steve
Matthew Fredrickson
On Feb 10, 2006, at 10:25 PM, Steve Underwood wrote:
> Matthew Fredrickson wrote:
>
>>
>> On Feb 10, 2006, at 1:21 PM, Gerard Saraber wrote:
>>
>>>
>>> Found it, going to go test it right now :) thanks!
>>> So far reports have been positive on the echo, but its a slow day ;)
>>> We're using cisco 7960 phones, they're pricy, but they work great and
>>> sound good, if it wasn't for the echo issue, I would have been able
>>> to
>>> roll the whole setup out already.
>>> Actually that's not quite true, I still have to make the 7914 addon
>>> module work with the 7960 phone, but that's not a show stopper.
>>>
>>> Either way, so far big thumbs up for the MG2 echo can, and if any
>>> developers read this, feel free to add a compile flag to make it more
>>> cpu intensive ;) and do more canceling.
>>>
>>
>> Does latest MG2 behave better than KB1 on your analog lines? I heard
>> in the past that in some cases (primarily with analog lines) that KB1
>> worked better. Also, have you tried the echotraining=800 (in
>> zapata.conf) tweak as well?
>
> A lot of the variability is probably due to thr lack of a DC blocker
> at the front of the echo canceller. As far as I remember, none of the
> cancellers in * has a DC blocker.
>
Where can one find out more information on writing a DC blocker? I
google'd around a bit, but couldn't find a definitive overview of what
one was, and how to write one. Thanks!
---
Matthew Fredrickson
Steve Underwood
>
> On Feb 10, 2006, at 10:25 PM, Steve Underwood wrote:
>
>> Matthew Fredrickson wrote:
>>
>>>
>>> On Feb 10, 2006, at 1:21 PM, Gerard Saraber wrote:
>>>
>>>>
>>>> Found it, going to go test it right now :) thanks!
>>>> So far reports have been positive on the echo, but its a slow day ;)
>>>> We're using cisco 7960 phones, they're pricy, but they work great and
>>>> sound good, if it wasn't for the echo issue, I would have been able to
>>>> roll the whole setup out already.
>>>> Actually that's not quite true, I still have to make the 7914 addon
>>>> module work with the 7960 phone, but that's not a show stopper.
>>>>
>>>> Either way, so far big thumbs up for the MG2 echo can, and if any
>>>> developers read this, feel free to add a compile flag to make it more
>>>> cpu intensive ;) and do more canceling.
>>>>
>>>
>>> Does latest MG2 behave better than KB1 on your analog lines? I
>>> heard in the past that in some cases (primarily with analog lines)
>>> that KB1 worked better. Also, have you tried the echotraining=800
>>> (in zapata.conf) tweak as well?
>>
>>
>> A lot of the variability is probably due to thr lack of a DC blocker
>> at the front of the echo canceller. As far as I remember, none of the
>> cancellers in * has a DC blocker.
>>
>
> Where can one find out more information on writing a DC blocker? I
> google'd around a bit, but couldn't find a definitive overview of what
> one was, and how to write one. Thanks!
>
DC in the signal through the echo canceller represents a signal the
canceller's adaption can never eliminate. It fights; it fails; it many
get very upset trying. DC needs to be eliminated before cancellation.
A-law/u-law ports are not supposed to give you any DC, but some do. The
following will estimate and remove DC from the signal. Prime
"dc_estimate" with zero.
int 16_t dc_removal(int32_t &dc_estimate, int16_t sample)
{
dc_estimate += ((((int32_t) sample << 15) - dc_bias) >> 9);
sample -= (dc_estimate >> 15);
return sample;
}
Its a first order noise shaped single pole IIR. '9' is the damping
factor. If you make it bigger, the low frequency response will improve,
but the estimate will take longer to settle after step changes. This may
affect initial convergence if a DC hiccup occurs as the line is picked
up. 9 should be a good starting point to try.
Regards,
Steve