Media5 Mediatrix 4104, Reference Manual

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Chapter 15 - Voice Transmissions Comfort Noise
244 Mediatrix 4104
Comfort Noise
Comfort Noise (CN) defines how the Mediatrix 4104 processes silence periods information it receives.
During silence periods, the Mediatrix 4104 may receive CN packets containing information about background
noise. When enabling Comfort Noise Generation (CNG), those packets are used to generate local comfort
noise.

To enable Comfort Noise:
1. In the voiceIfMIB , locate the voiceIfTable group.
2. Define the type of comfort noise in the voiceIfG711ComfortNoiseGenerationEnable variable.
The following settings are available:
3. Restart the Mediatrix 4104 so that the changes may take effect.
User Gain
The user gain allows you to modify the input and output sound level of the Mediatrix 4104.
You can compensate with the user gain if there is no available configuration for the country in which the
Mediatrix 4104 is located. Because the user gain is in dB, you can easily adjust the loss plan (e.g., if you need
an additional 1 dB for analog to digital, simply put 1 for user gain input).

To set user gain variables:
1. In the voiceIfMIB , locate the voiceIfTable group.
2. Define the following variables:
• voiceIfUserInputGainOffset : User input gain offset in dB (from analog to digital).
Standards Supported • RFC 3389: Real-time Transport Protocol (RTP) Payload for
Comfort Noise (CN)
Note:
Comfort noise only applies to the G.711 and G.726 codecs. G.723 and G.729 CNG is not
configurable because it is part of the codec.
Table 160: Comfort Noise Settings
Setting Description
disable CNG disabled.
whiteNoise CNG enabled – white noise.
customNoise CNG enabled – custom noise. More elaborated background noise that
sounds better than white comfort noise.
Caution:
Use these settings with great care. Media5 recommends not to modify the user gain variables
unless absolutely necessary because default calibrations may not be valid anymore.
Modifying user gains may cause problems with DTMF detection and voice quality – using a high user gain
may cause sound saturation (the sound is distorted). Furthermore, some fax or modem tones may not be
recognized anymore. The user gains directly affect the fax communication quality and may even prevent a
fax to be sent.
In the Unit Manager Network Administration Manual , refer to chapter Ports Parameters , section Port
Configuration Window .