Media5 Mediatrix 4104, Reference Manual

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Chapter 15 - Voice Transmissions DTMF Detection
240 Mediatrix 4104
Raising this value increases the sensitivity of the DTMF detection. Raising this value too high may
also cause false detections of DTMFs.
2. Set the minimum absolute power threshold (dBm0) for the low and high frequencies in a DTMF in
the
voiceIfDtmfDetectionUnitMinPowerThreshold variable.
The high AND low DTMF frequencies MUST be higher than this threshold otherwise the DTMF is
not detected.
You could, for instance use one of the following settings:
• -15 dBm0: This configuration detects even more false DTMFs in the voice pattern.
• -20 dBm0: This configuration detects more DTMFs in the voice pattern.
• -35 dBm0: his configuration detects less DTMFs in the voice pattern.
• -40 dBm0: This configuration detects even less DTMFs in the voice pattern.
Raising this value reduces the sensitivity to DTMF detection.
3. Set the break absolute power threshold (dBm0) for on-off transition of a DTMF in the
voiceIfDtmfDetectionUnitBreakPowerThreshold variable.
While a DTMF has been positively detected, the DTMF will be considered OFF as soon as the high
OR low frequency in the DTMF gets below this threshold.
4. Set the voiceIfDtmfDetectionUnitPositiveTwist variable.
When the high-group frequency of a DTMF is more powerful than the low-group frequency, the
difference between the high-group frequency absolute power and the low-group frequency absolute
power must be smaller than or equal to the value set in this variable. Otherwise, the DTMF is not
detected.
Raising this value increases the sensitivity of DTMF detection. Raising this value too high may also
cause false detections of DTMFs.
5. Set the voiceIfDtmfDetectionUnitNegativeTwist variable.
When the low frequency of a DTMF is more powerful than the high frequency, the difference
between the low frequency absolute power and the high frequency absolute power MUST be
smaller than or equal to the value set in this variable. Otherwise, the DTMF is not detected.
Raising this value increases the sensitivity of DTMF detection. Raising this value too high may also
cause false detections of DTMFs.
6. Define how the Rise Time criteria should be configured for DTMF detection in the
voiceIfDtmfDetectionRiseTimeCriteria variable.
The Step Rise criteria compares the current frame energy to the high frequency power of the
previous frame. If the current frame energy is high enough, then it passes the test, further validating
the DTMF.
Disabling the Step Rise criteria may result in deteriorated talk-off performance, but increases the
detection of malformed DTMF.
The Confirm DTMF SNR criteria is an additional Signal-to-noise ratio test performed before a
confirmed DTMF report is sent to finally validate the DTMF.
Table 155: RiseTimeCriteria Parameters
Parameter Description
checkSr Enable the Step Rise criteria and disable the Confirm DTMF SNR criteria.
confirmSnr Enable the Confirm DTMF SNR criteria and disable the Step Rise criteria.