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Jalal
Vetran
Joined: April 24 2006
Location: Iran
Posts: 188
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| Posted: June 24 2007 at 10:20am | IP Logged
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Dear Support,
Comfort Noise Generator (CNG) algorithm allows the insertion of an artificial noise during silent intervals of speech. This option is useful when the caller has enabled VAD (Voice Activity Detection).
This feature is necessary to avoid noise modulation introduced when the transmission is switched off. If the background acoustic noise that was present during active periods abruptly disappears, this very unpleasant noise modulation may even reduce the intelligibility of the speech. The purpose of the VAD is to reliably detect the presence or absence of speech and to convey this information to the CNG algorithm. The purpose of the CNG algorithm is to create a noise that matches the actual background noise with a global transmission cost as low as possible.
See following links for more information on this issue.
http://en.wikipedia.org/wiki/Comfort_noise
http://www.gaoresearch.com/products/telephony/other/vad_cng. php
Regards,
Jalal
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Jalal
Vetran
Joined: April 24 2006
Location: Iran
Posts: 188
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| Posted: July 03 2007 at 1:08am | IP Logged
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You did not write any note about this subject!
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support
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Joined: January 26 2005
Location: United States
Posts: 1666
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| Posted: July 03 2007 at 7:16am | IP Logged
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Hi jalal,
Using Wikipedia http links in your postings is a good idea. :)
We know what Comfort Noise Generation is. However….
1) What exactly is your question?
2) Specifically what would you like us to update and/or change in the VOIP Media Engine product?
Note: It is very busy here so free support forum responses may be a bit longer than usual this week.
Thanks,
Support
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Jalal
Vetran
Joined: April 24 2006
Location: Iran
Posts: 188
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| Posted: July 03 2007 at 7:37am | IP Logged
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Hi,
I did write "You did not write any note about this subject" sentence in my previous note because I thought maybe you have forgot this post.
What exactly we want is to add this feature in your next release. This feature can be disabled by default and be enabled with a API function as needed.
This is not a critical feature for us but it's a good option that most of VOIP softwares in the market have.
BTW: I know you are busy always, but I had requested a update for more than 10 days and I have not get any reply from you to mention you are busy. I think these busy days will never be finished.
Regards,
Jalal
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support
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Joined: January 26 2005
Location: United States
Posts: 1666
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| Posted: July 03 2007 at 8:42am | IP Logged
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Jalal,
Thanks for your response. If you can, describe a bit about how you would like the media engine to handle comfort noise generation.
What I mean is: Try to describe the audio signal paths that we would want to have comfort noise generation enabled.
For example:
Let’s assume that two call endpoints do not transmit RTP to each other due to RTP transmit VAD (but only periodically send RTP silence packets for RTP NAT keep alive). In this case, each user agent will not receive any audibly detectable media from the other and the user’s experience will be that the line is completely dead (i.e. totally silent).
To give the user the feeling that the line is still connected, all we would have to do is mix to the internal playback mechanism of the media engine comfort noise media to give a bit of background noise. This would give the user the sense that the line is still connected event though no audible RTP media is flowing from end-to-end. So the question is:
Question 1:
Is CNG for local playback only via multimedia hardware?
Any thoughts you have would be good to hear. This is not a hard issue to incorporate into the media engine and we could do it easily.
I you have a favorite C/C++ CNG algorithm, point it out to us and we will test it. Maybe it will get into the product.
We have now made a note of this request on the development schedule.
Question 2:
By the way, what version of the media engine are you guys using now?
Support
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Jalal
Vetran
Joined: April 24 2006
Location: Iran
Posts: 188
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| Posted: July 03 2007 at 9:42am | IP Logged
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Hi,
1- What you described about CNG is what exactly we want. I think generating Comfort Noise has no other use unless when one is listening to the received RTP media streams through Sound Hardware. So I think mixing the Noise with the playing voice on the Sound Hardware is a good option. Another option would be just playing sound when no RTP is received. I mean do not mix the Noise always just play the Noise when there is really a Silence.
2- We are currently using v5.12.3.30 .
Regards,
Jalal
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support
Administrator
Joined: January 26 2005
Location: United States
Posts: 1666
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| Posted: July 03 2007 at 11:15am | IP Logged
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Jalal,
Item 1:
Yes, exactly.
Item 2:
OK
Support
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Jalal
Vetran
Joined: April 24 2006
Location: Iran
Posts: 188
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| Posted: July 05 2007 at 12:44am | IP Logged
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Hi,
Item 2:
What do mean by OK? When will you upgrade us? :(
Jalal
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support
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Location: United States
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| Posted: July 05 2007 at 8:00am | IP Logged
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We will get you the latest minor upgrade when it is ready. It has not been officially released.
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Jalal
Vetran
Joined: April 24 2006
Location: Iran
Posts: 188
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| Posted: January 20 2008 at 1:23am | IP Logged
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Hi,
About CNG recently when I was working with Alcatel VOIP PBX I found that there is a RTP Payload type for Comfort Noise. When I searched it on the net I found there is a RFC for this.
See : rfc3389.txt
This RTP payload type is sent by the time Silence is detected on the voice path to let destination know about this silence and play some comfort noise till next RTP payload is received.
Regards,
Jalal Abedinejad
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support
Administrator
Joined: January 26 2005
Location: United States
Posts: 1666
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| Posted: January 21 2008 at 12:28pm | IP Logged
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Jalal,
Thanks for this additional information. We will keep note of it.
Just for curiosity sake, on a scale of 1 to 10 (10 representing a needed critical feature), how would you rank the need for CNG overall?
Thanks Jalal,
Support
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Jalal
Vetran
Joined: April 24 2006
Location: Iran
Posts: 188
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| Posted: January 21 2008 at 11:04pm | IP Logged
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Hi,
From my point of view 5 is a good rank but from end users view is 10. That is because when they hear nothing when other party does not speak they would think call is dropped while it is not really dropped.
Regards,
Jalal
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LanScape Support Forum -> LanScape VOIP Media Engine™
Topic: Comfort Noise Generation
