[Freeswitch-users] Removing echo.

Tue Mar 19 21:34:20 MSK 2013

2 problems with it.  First, it's GPL.  Second, it's a line echo canceller.

On Tue, Mar 19, 2013 at 2:27 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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>>  ****
>>
>>
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>>
>> ****
>>
>>  ****
>>
>> --
>> Anthony Minessale II
>>
>> FreeSWITCH http://www.freeswitch.org/
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>>
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>>
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>>
>>
>> _________________________________________________________________________
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>>
>> 
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>>
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>>
>> ****
>>
>> ** **
>>
>> --
>> Anthony Minessale II
>>
>> FreeSWITCH http://www.freeswitch.org/
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>> Twitter: http://twitter.com/FreeSWITCH_wire
>>
>> AIM: anthm
>> MSN:anthony_minessale at hotmail.com
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>> IRC: irc.freenode.net #freeswitch
>>
>> 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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>> ** **
>>
>> _________________________________________________________________________
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>> http://www.freeswitchsolutions.com
>>
>> 
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>
> _________________________________________________________________________
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>
> 
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