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In this section:

 

Use this object to specify the characteristics of the DSP Packet Assembler/Disassembler (PAD) resources in the SBC. DSP PAD is used for transcoding between different media codecs and/or different packetization times, detecting fax and/or modem tones, interworking DTMF transport modes, and detecting DTMF digits.

The following audio codecs are supported in the SBC DSP PAD:

Playout Buffer Sizing Chart

Codec
Playout Buffer
Length (ms)
Number of
Frames
Frame Size
(bytes)
Total Size
(bytes)
G.71140040803200
G.711 Side B40040803200
G.72640040602400
G.7295005010500
G.723150050241200
iLBC 20ms5002050950
iLBC 30ms60025321000
AMR/EFR5002532875
EVRC/EVRC-B5002522550
G.72240040803200
G.722.140020801600
G.722.240020621230
Opus40040300

12000

A packet outage is the loss of incoming voice (RTP) packets. If the PAD on the server module detects a packet outage that exceeds the PACKET OUTAGE THRESHOLD, a "set" trap is generated after the call is disconnected. The set trap displays a count for the total outage occurrences on the shelf and the slot of the affected module. Ten seconds after the last detected outage, a "clear" trap is generated to indicate that the condition has not occurred for a 10 second interval on the shelf and the slot. A counter for the occurrences within the interval is displayed in the clear trap. A total occurrence counter increments with every packet outage that exceeds the threshold on the server. The counter can be reset using PACKET OUTAGE RESET TOTAL COUNTER.

Packet outage cannot be detected if T.38 is used in a call. Calls that use a silence suppression algorithm need to specify a heartbeat of an appropriate interval to detect outages.

For an example of configuring the playout time series parameters, see Configuring Playout Time Series Period and Thresholds.

Command Syntax

% set system dspPad  
	audioTxDuring2833 <disabled|enabled>
	comfortEnergy <-90dBm to -35dBm>
	highPriorityCompressionReservation <percentage>
	highPriorityToneReservation  <percentage>
	jitterEvalPeriod <period in milliseconds>
	jitterMinOccThsh <threshold in milliseconds>
	playoutTimeseriesPeriod <period in milliseconds>
	playoutTimeseriesThreshold0 <threshold in milliseconds>
	playoutTimeseriesThreshold1 <threshold in milliseconds> 
	playoutTimeseriesThreshold2 <threshold in milliseconds>
	rtpDtmfRelay <#>
	sidHangoverTime <time in milliseconds>
	sidMaxNoiseFloor <-62dBm to -24dBm>
	sidMaxTime <time in milliseconds>
	sidMinNoiseFloor <-62dBm to -24dBm>
	sidMinTime <time in milliseconds>
	toneThreshold <percentage>
	toneThresholdState
	<disabled|enabled>
	universalCompressionThreshold <percentage>
	universalCompressionThresholdState <disabled|enabled>

Command Parameters

DSP Pad Resources Parameters

Parameter

Length/Range

Description

audioTxDuring2833

N/A

Use this flag to specify the Audio Transmit state during RFC2833.

  • disabled
  • enabled (default)

comfortEnergy

-90 to -35 (dBm0)

The initial estimate used for generating comfort noise when the CODEC in the Packet Service Profile is G.711 or G.711SS. For G.711, when no modem has been detected, this represents the level of comfort noise to fill in the audio when packet loss occurs. This plays until the first packet is received. Whenever there is a drop in packets (packet loss or silence periods), the G.711SS represents the level of comfort noise when no SID is received. (default = 56 [which represents -56 dBm0]).

highPriorityCompressionReservation0 - 100Percentage of compression resources (default = 0) reserved for high priority calls.
highPriorityToneReservation0 - 100Percentage of tone resources (default = 0) reserved for high priority calls.

jitterEvalPeriod

10-300000

Time period (in milliseconds) to decide when to periodically evaluate playout occupancy. This parameter determines the rate at which the jitter buffer is adapted.
If the value is too small, then the jitter buffer algorithm may tend to discard samples too aggressively causing small losses of audio. If the value is too large, then the excess delay built up in the jitter buffer will remain for a long time before it can be removed. (default = 1000).

jitterMinOccThsh

2-200

The minimum jitter buffer occupancy threshold (in milliseconds) below which the playout time advances if the occupancy has existed for the jitterEvalPeriod.

This value should be target minimum occupancy of the buffer, assuming the actual network jitter is small enough to reach this number.

The minimum occupancy of the jitter buffer over time represents the delay added before audio is played out to the PSTN. The value is used to prevent excess delay from building up in the jitter buffer. If the network jitter is small enough, occupancy will gradually be brought down to this level or possibly lower. The expected jitter threshold should be set to equal or slightly larger than the jitter to obtain minimum delay. If the actual jitter is higher, then some samples may (infrequent) be discarded, depending on the statistics of the signal. If the actual jitter is somewhat smaller, then some accumulated delay (less than or equal to this value will be formed) in the jitter buffer. This represents the trade-off between maintaining minimum delay and discarding samples. (default = 20). Setting this number to 200 disables jitter buffer adaptation.

playoutTimeseriesPeriod

10000-240000

Specifies the recording interval size (in milliseconds) used by the SBC when monitoring RTP playout buffer quality; used only when an RTP stream is terminated. This parameter applies only to the RTP playout buffer in the DSP and does not apply to the RTP monitoring function in the network processor. (default = 20000 [or 20 seconds]).

playoutTimeseriesThreshold0

N/A

Specifies the playout loss time series threshold (in milliseconds) used by the SBC when quantifying packet loss as applied to the playoutTimeseriesPeriod.

Loss durations less than or equal to Threshold0 are considered Good. Loss durations greater than Threshold0 and less than Threshold1 are considered Acceptable. The default value is "0", or 0 percent of the playoutTimeseriesPeriod.

This parameter is applicable for all channel instances.

playoutTimeseriesThreshold1

N/A

Specifies the playout loss time series threshold (in milliseconds) used by the SBC when quantifying packet loss as applied to the playoutTimeseriesPeriod.

Loss durations greater than Threshold0 and less than Threshold1 are considered Acceptable. Loss durations greater than Threshold1 and less than Threshold2 are considered Poor. The default value is "200" (0.2 seconds, or 1 percent of the playoutTimeseriesPeriod).

This parameter is applicable for all channel instances.

playoutTimeseriesThreshold2

N/A

Specifies the playout loss time series threshold (in milliseconds) used by the SBC when quantifying packet loss as applied to the playoutTimeseriesPeriod.

Loss durations greater than Threshold1 and less than Threshold2 are considered Poor. Loss durations greater than Threshold2 are considered Unacceptable. The default value is "600" (0.6 seconds, or 3 percent of the playoutTimeseriesPeriod).

This parameter is applicable for all channel instances.

rtpDtmfRelay

0-127

This integer specifies the RTP payload type to use for DTMF Relay during compressed calls. When running RFC 2833 with H.323 or SIP signaling, H.323 disallows 0-95. (default = 100).

sidHangoverTime

80-2560

This integer specifies the minimum time (in milliseconds), after voice is detected inactive before sending a SID packet. (default = 300).

sidMaxNoiseFloor

24-62

This (positive) integer specifies the maximum noise level; above this noise level is considered to be speech (in dBm0s). (default = 48 [which represents -48 dBm0]).

sidMaxTime

50-300000

This integer specifies the maximum time between SID packets (in milliseconds). If SID HEARTBEAT in the Packet Service Profile is enabled, the SID packets will be sent during silence intervals lasting longer than the value specified by this parameter. These packets can be used to keep a minimum level of bearer traffic flowing for RTCP calculation purpose. This value must exceed the sidMinTime (below). (default = 2000, or 2 seconds).

sidMinNoiseFloor

24-62

This (positive) integer specifies the minimum noise level; below this noise level is considered to be silence (in dBm0s). (default = 60 [which represents -60 dBm0]).

sidMinTime

50-300000

This integer specifies the minimum time between SID packets, in milliseconds. This ensures that SID packets are not sent too frequently when the background noise is changing, but instead some minimum amount of compression still occurs. (default = 200).

toneThreshold

1-100

The percentage of threshold crossing value for tone resources. (default = 90).

toneThresholdState

N/A

The state of the tone threshold event.

  • disabled
  • enabled (default)

universalCompressionThreshold

1-100

This positive integer specifies the percentage of usage the usage threshold for universal compression resources in the node. When this usage level or threshold is reached, an event (and possibly a trap) will be generated. (default = 90).

universalCompressionThresholdState

N/A

When this flag is enabled, a trap is generated when universal compression resources are reduced beyond the configurable universalCompressionThreshold value.

  • disabled
  • enabled (default)

Command Example

To display the DSP PAD resources parameters:

% show system dspPad   
	jitterEvalPeriod                   1000;
	jitterMinOccThsh                   20;
	rtpDtmfRelay                       100;
	sidMinTime                         200;
	sidMaxTime                         2000;
	sidHangoverTime                    300;
	sidMinNoiseFloor                   60;
	sidMaxNoiseFloor                   48;
	comfortEnergy                      56;
	universalCompressionThreshold      90;
	universalCompressionThresholdState enabled;
	playoutTimeseriesPeriod            20000;
	playoutTimeseriesThreshold0        0;
	playoutTimeseriesThreshold1        200;
	playoutTimeseriesThreshold2        600;
	toneThreshold                      90;
	toneThresholdState                 enabled;
	audioTxDuring2833                  enabled;
	highPriorityCompressionReservation 10;
	highPriorityToneReservation        10;