[Freeswitch-users] Removing echo.

Anthony Minessale anthony.minessale at gmail.com
Tue Mar 19 21:44:26 MSK 2013 

I think its a kernel mod no?  So its irrelevant about the license.  People
use it with FS today but only with Dhadi which is the one place its easy to
install.

We do have some DSP code in the new webrtc repo in addition to all of
Steve's spandsp code.
Its not hard to add some audio tuning code its just hard to make sure its
effective from a server perspective.

It for sure a good idea to add it to mod_portaudio for instance.



On Tue, Mar 19, 2013 at 1:27 PM, Vitalie Colosov <vetali100 at gmail.com>wrote:

> Before the thread dies I would like to add to this subject that there is
> an Open Source echo canceler exists: Oslec
> As written on their site it already works with "*You*-*Know-Who*"... :)
> Has anyone seriously considered integrating it into FreeSWITCH?
>
>
> 2013/3/19 Sean Devoy <sdevoy at bizfocused.com>
>
>> Anthony and Spencer,****
>>
>> ** **
>>
>> Thanks for your responses. Anthony the megaphone analogy really worked
>> for me.  Spencer thanks for saving me the time of looking up those settings.
>> ****
>>
>> ** **
>>
>> I agree cell phones frequently have huge echo.  The longer the echo delay
>> (aka higher latency) the harder it is to correct makes perfect sense as
>> well.****
>>
>> ** **
>>
>> I actually had a chance to talk to one of the users experiencing this
>> problem.  Bear in mind I usually get to talk to her boss who is looking for
>> reasons to not pay his bill.  She said they do still “occasionally” get
>> echo but it is not too bad.  She said it is always worse when the call
>> certain people (that correlate’s with end user device problems).  Then she
>> mentioned I was one of the ones they usually get echo with and it was
>> happening now, but not that bad!****
>>
>> ** **
>>
>> Opportunity knocked, so I jumped in!  First a quick note of reference – I
>> have moderately high hearing loss and wear hearing aids.  I keep my headset
>> turned up fairly high!  I asked the user who called me to talk to herself
>> while I did some tests and tell me if the echo got better or even went
>> away. Low and Behold – mute made it go away COMPLETELY.  As much as I hate
>> it when Anthony is right, it is hard to deny it.  I tested further and each
>> of these things helped enough that she noticed:  Turning my headset speaker
>> down on the inline volume control, turning the headset speaker down at the
>> phone, turning my microphone boost down (this headset has 3 settings for
>> microphone level), muting at the phone or on the inline headset control.
>> All of those things taken collectively say “Listen to Anthony butthead.”*
>> ***
>>
>> ** **
>>
>> So, assuming the cause of the echo is beyond my control (e.g. someone
>> else’s phone) are we just screwed or is it just cost prohibitive?  I would
>> rather reply that it would cost $5000 to fix it than say “can’t be helped.”
>> ****
>>
>> ** **
>>
>> Suppose the user detects bad echo.  Is there anything we could do
>> (assuming they could notify FS through a programmable key or even web link,
>> etc)?  Could we drop the gain to and from the remote end?****
>>
>> ** **
>>
>> I promise to let this die now.  Let me here your final thoughts.****
>>
>> ** **
>>
>> Thanks again for your time and patience.****
>>
>> ** **
>>
>> *From:* freeswitch-users-bounces at lists.freeswitch.org [mailto:
>> freeswitch-users-bounces at lists.freeswitch.org] *On Behalf Of *Spencer
>> Thomason
>> *Sent:* Tuesday, March 19, 2013 11:40 AM
>>
>> *To:* FreeSWITCH Users Help
>> *Subject:* Re: [Freeswitch-users] Removing echo.****
>>
>> ** **
>>
>> Hi Sean,****
>>
>> We were experiencing a similar problem with these units and were able to
>> verify that it was in fact the remote end but the threshold of the echo
>> canceler seems to be too low by default.  We could hear echo and then
>> unplug the handset from the base on the other end, without muting, and the
>> echo would stop.  We found that decreasing the gain slightly all but
>> eliminated complaints.  This does reduce the level slightly but in our
>> traces it was close to on par with an analog handset.  The pertinent
>> configuration options are:****
>>
>> ** **
>>
>>   <Handset_Input_Gain>-6</Handset_Input_Gain>
>>   <Headset_Input_Gain>-6</Headset_Input_Gain>
>>   <Speakerphone_Input_Gain>-6</Speakerphone_Input_Gain>
>>   <Handset_Additional_Input_Gain>0</Handset_Additional_Input_Gain>
>>   <Headset_Additional_Input_Gain>0</Headset_Additional_Input_Gain>
>>
>> <Speakerphone_Additional_Input_Gain>0</Speakerphone_Additional_Input_Gain>
>> ****
>>
>> ** **
>>
>> Thanks,****
>>
>> Spencer****
>>
>> ** **
>>
>> ** **
>>
>> On Mar 19, 2013, at 7:49 AM, Anthony Minessale wrote:****
>>
>>
>>
>> ****
>>
>> Sean,****
>>
>> ** **
>>
>> You are welcome to disagree.  Science is driven by people being unwilling
>> to accept things as they are.****
>>
>> I do have some explanations for you if you are interested.****
>>
>> ** **
>>
>> Cisco and Linksys ATA both have echo cancelers in them at the point where
>> the analog data is converted to digital.  This is the ideal place for it as
>> I mentioned earlier.  So they actually are doing something about the
>> problem and that is why you do not observe one.  Getting echo while using a
>> cell phone is also very common.  The more latency and conversion of the
>> audio data you experience, the more likely you can have echo.  (iPhone is
>> notorious) The other place where its important to have echo cancellation is
>> the point where the digital data in the rtp stream is transferred into the
>> TDM gateway interfacing with the PSTN.  This is why most TDM cards like
>> Digium and Sangoma have onboard echo canceler chips.  We are not completely
>> helpless, we can do some unnatural things like decode the audio signal we
>> are passing through and try to run some echo cancellation on it but, in the
>> conditions you describe where you hear a perfect replica of what you are
>> saying 2-5 seconds later only softer.  That is for sure outside the range
>> of any echo canceler.  It cannot reliably tell that this clean signal
>> coming many seconds later should be filtered out because its a replica of
>> data that has already passed by long before.  Usually in this type of
>> issue, you are actually hearing the other side hear what you said.  So you
>> say the statement, the latency takes its toll and the echo is coming back
>> at you from the far end as they are hearing it.  ****
>>
>> ** **
>>
>> I am open to options.  We do have some work on doing some inline audio
>> processing underway but we should not rely on them if we can possibly
>> control the surroundings better first.  If you are talking to me in the
>> same room using a megaphone and I am wearing ear plugs.  Its easier to tell
>> you to turn off the megaphone and tell me to remove the ear plugs.****
>>
>> ** **
>>
>> ** **
>>
>> ** **
>>
>> ** **
>>
>> On Mon, Mar 18, 2013 at 9:24 PM, Sean Devoy <sdevoy at bizfocused.com>
>> wrote:****
>>
>> Hey Anthony,****
>>
>>  ****
>>
>> Does that mean PBXMate is not worth investigating?****
>>
>>  ****
>>
>> I have to disagree here. Placing the blame entirely on the phones at the
>> other end doesn’t hold water for me.  I have had echo problems calling from
>> my cell phone when leaving a voice mail on FS where there is no phone at
>> the other end. So clearly there are situations where it ain’t just the
>> phone at the other end.  It also leaves no explanation why Cisco Phones and
>> Linksys ATAs don’t have the same problem with Commercial Venders like
>> Vonage.  They don’t have anything different at the end of the line for echo
>> cancellation then FS does. I have also had users confirm they are still
>> getting echo with the microphone MUTED on my end.****
>>
>>  ****
>>
>> Again, I love FS and I am not trying to bash anyone or any code.  I am
>> just saying there has to be more to this puzzle.  I know what a crappy
>> speaker phone’s echo sounds like and I am not at all concerned about that.
>> Crappy speaker phones sound like crappy speaker phones no matter what. I
>> don’t think that’s what I am trying to track down.  These are business call
>> where 90% are using the standard handset on business quality phones.  It
>> happens at various levels, but when it is at the bad end of the spectrum
>> (e.g. long delay and loud), it does not sound like echo off of walls coming
>> back in a microphone.  It is like my input channel has been delayed,
>> softened and looped directly back to me crystal clear.  Maybe it is one of
>> my VOIP providers’ hardware or software and is load dependent, but the
>> problem exists outside of cheap phones. And of course it is only
>> reproducible on 3 calls in a hundred at peak usage hours, making it a
>> nightmare to track or diagnose.  But those 3 calls are the ones my
>> customers want to talk about at billing time.****
>>
>>  ****
>>
>> Now, I have just thrown that all out there is hopes that 50 people will
>> say “That absolutely never happens to me with FS” so I can look at it a
>> different way.****
>>
>>  ****
>>
>> Thanks for your thoughts.****
>>
>> Sean****
>>
>>  ****
>>
>> *From:* freeswitch-users-bounces at lists.freeswitch.org [mailto:
>> freeswitch-users-bounces at lists.freeswitch.org] *On Behalf Of *Anthony
>> Minessale
>> *Sent:* Monday, March 18, 2013 7:30 PM****
>>
>>
>> *To:* FreeSWITCH Users Help
>> *Subject:* Re: [Freeswitch-users] Removing echo.****
>>
>> ** **
>>
>>  ****
>>
>> The best place for echo cancelation is in the clients as close to the mic
>> as possible.****
>>
>> Someone asked why skype and some apps are better.  It's because they have
>> echo cans in the client app.****
>>
>> Sip soft phones are basically toys unless they have some kind of advanced
>> gain and echo controls on your pc because that is where your mic is and
>> could have the vol turned up too high etc.****
>>
>>  ****
>>
>> From FS perspective in the middle, we can't tell its echo or not because
>> we are just passing the data along and we're typically getting it 30-70 ms
>> too late.  ****
>>
>>  ****
>>
>>  ****
>>
>> In general, you don't get echo when using real phones because they have
>> proper hardware and software to deal with the place where the audio is
>> being sampled and rendered.****
>>
>>  ****
>>
>>  ****
>>
>>  ****
>>
>>  ****
>>
>>  ****
>>
>> On Mon, Mar 18, 2013 at 5:15 PM, Christopher Rienzo <cmrienzo at gmail.com>
>> wrote:****
>>
>> Echo cancellation is not easy.  The only open source one I've seen is GPL
>> (making it license incompatible with FreeSWITCH) and is not suitable for
>> handling echo over IP networks.  Perhaps tricks are being played using VAD
>> to only allow only one speaker at a time in the ooVoo conference?****
>>
>> ** **
>>
>> On Mon, Mar 18, 2013 at 5:53 PM, Mimiko <vbvbrj at gmail.com> wrote:****
>>
>> Today we tried ooVoo conference system with theirs client using same
>> boxes and microphones - again, no echo. How this can be? Is it only
>> commercial products have echo removing function?****
>>
>>
>> --
>> Mimiko desu.
>>
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>>  ****
>>
>>
>> _________________________________________________________________________
>> Professional FreeSWITCH Consulting Services:
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>> http://www.freeswitchsolutions.com
>>
>> 
>> 
>>
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>>
>>
>> ****
>>
>>  ****
>>
>> --
>> Anthony Minessale II
>>
>> FreeSWITCH http://www.freeswitch.org/
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>>
>> AIM: anthm
>> MSN:anthony_minessale at hotmail.com
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>>
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>>
>>
>> _________________________________________________________________________
>> Professional FreeSWITCH Consulting Services:
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>> http://www.freeswitchsolutions.com
>>
>> 
>> 
>>
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>>
>>
>> ****
>>
>> ** **
>>
>> --
>> Anthony Minessale II
>>
>> FreeSWITCH http://www.freeswitch.org/
>> ClueCon http://www.cluecon.com/
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>>
>> AIM: anthm
>> MSN:anthony_minessale at hotmail.com
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>>
>> FreeSWITCH Developer Conference
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>> googletalk:conf+888 at conference.freeswitch.org
>> pstn:+19193869900 ****
>>
>> _________________________________________________________________________
>> Professional FreeSWITCH Consulting Services:
>> consulting at freeswitch.org
>> http://www.freeswitchsolutions.com
>>
>> 
>> 
>>
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>>
>> ** **
>>
>> _________________________________________________________________________
>> Professional FreeSWITCH Consulting Services:
>> consulting at freeswitch.org
>> http://www.freeswitchsolutions.com
>>
>> 
>> 
>>
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>
> _________________________________________________________________________
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> http://www.freeswitchsolutions.com
>
> 
> 
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-- 
Anthony Minessale II

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AIM: anthm
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