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New Member

C20 echo issue

Hi all:

         Here is the scenario: I have a meeting room ,2 TV sets and a suit of audio.My c20 have the connection to the audio system,which means the voice of the telepresence can be out from the audio system,also my c20 have two Micro ,my tv sets which dispaly the image can also be the voice source of the telepresence system.

          Now there is an issue ,when I mute the tv's audio,just only the meeting room's audio system working ,there is no echo,when I unmute the tv's audio there is echo.When I mute the meetingroom's audio system,just the tv sets' audio working,echo again.

          I have no experience on this issue.

          Any help or suggestion will be appreciated.

Everyone's tags (2)
New Member

C20 echo issue


which ports have you used to connect the audio system and the TV?

We have noticed that on some screens we get echo when the screen gets the audio over the HDMI cable.

If you use the HDMI cable for the TV's audio in, try to use the external audio connectors on the C20 instead to see if the issue persists.

C20 echo issue

Many TV sets have some audio enhancement capabilities, most likely also yours.

See if you can disable that, sometimes its in the audio menu, sometimes its (not) present

on specific inputs, sometimes you might not be able to remove it, ...

If such a "feature" is present and active it will break the echo supression.

I would only use one audio system at a time as both might add different delays.

Could you describe "voice source of video conferencing sytem"?

Could you describe echo, the remote site hears it or do you hear something in the room with

the tv screen you mute/unmute. Is it an echo or a feedback (feeeeeeeep)?

Please remember to rate helpful responses and identify

New Member

C20 echo issue

voice source of video conferencing sytem: It should be the audio system.There are two voice source ,TV and audio system.

echo: as the description of my custome,he can here his voice again and again.

There appears another question,the remote sides can here the sounds like the wind folw (fufufufufuf ro huhuhuhuh).


Re: C20 echo issue


I had uploaded a checklist which you can go through. It would help you to step by step check each & everything that could be wrong. If you're using a C20, then the Echo Canceller is not present. Hence, the TV enhancements would not apply in your case. Please check the checklist below and let us know if after following it, you're still facing this issue :


Mubashshir Akhtar

Thanks Mubashshir Akhtar
New Member

C20 echo issue

The C20 does have 1 Echo Canceller, present on MIC input. It does not have extra ECs...

You could try to adjust the Echo Delay, using the command: xcommand experimental Audio EcReferenceDelay:

If you change the delay (0 a 300 ms), test all kind of calls and situations inside the room.

Just as information...

We had this issue with one TV with no customizable audio features. When we use HDMI audio on TV and the MIC is near the TV, we don´t have echo (yes, MIC near the TV, the opposite as all instructions). If we put the MIC far from TV, it look like the sound runs over the walls and the C20 cannot avoid the Echo. Adjusting the Delay, que can fix this, but it only works when the MIC is far from TV and it is other End dependant (with adjusted delay, we cannot move the MIC close to the TV again because in this case the Echo will back and depends wich kind of EP is connected to).

The workarroud was to use an external audio device (not to use the TV sound over HDMI).



New Member

C20 echo issue

Thans for your information.Your information is very helpful to me.

The echo canceller can affect both the micr or just only one of them? If just one,which one ?

Cause in my case ,my c20 have 2 micro ,one is near the tv,the other one if far from the TV.

Refer to the other answer,Maybe it's my TV set's sound effect,This TV is new type.

There appears another question,the remote sides can here the sounds like the wind folw (fufufufufuf ro huhuhuhuh).

Have you meet this?

New Member

C20 echo issue

Yeah I download thad doc.May be it's the TV's sound effect.

There appears another question,the remote sides can here the sounds like the wind folw (fufufufufuf ro huhuhuhuh).

have you meet this?

New Member

C20 echo issue

Audio system: the interface just besides the mic inputs.

TV :     It should be the hdmi,and I didn't modify the relevant parameter.So the voice should be passed by the hdmi.

And the audio system is working well without echo,when I use the TV's Audio echo appres.Maybe due to  TV's audio effect, the Echo Canceller can't work well.

C20 echo issue


This is a known issue with many consumer level displays, see below for some advice:

Cisco has put in a lot of effort to minimize the camera to screen delay on our TelePresence endpoints.

New consumer TVs are usually equipped with “Motion Flow” or similar technology to insert new video frames between standard frames to create smoother images. This processing takes time and to maintain lip synchronization, the TV will delay the audio so that the audio and video arrives at the same time.

The echo canceller in the Cisco endpoints can handle such delay up to 30 ms. Many consumer TVs are not made for real time video communication and may introduce more than 30 ms of delay.

If you use such a TV together with a C Series codec it is recommended that you turn off “Motion Flow”, “Natural Motion” or any other video processing that introduces additional delay.

Some consumer TVs also support advanced audio processing like “Virtual Surround” effects and “Dynamic Compression” to improve the TV experience. Such processing will make any acoustic echo canceller malfunction and should hence be switched off.

Some monitors are equipped with a setting called ‘Game Mode’. This mode is specifically designed to help reduce the response time and will usually help to reduce the delay.



Thank you, Justin Ferello Technical Support Specialist KBZ, a Cisco Authorized Distributor e/v: