The following parameters describe the configuration of a VoIP endpoint. You can define these parameters and they are useful for debugging and logging purposes because they capture the state of the endpoint.

• CI—Codec ID. A string or a number that identifies the voice codec which is currently used in the call.

• FM—Frame size. Native frame size, in milliseconds (ms), of the selected codec. An example of a frame size and codec combination is G.729a/30ms. For the G.711 codec, the frame size is a value that you can define in the voice dial peer. For example, G.711 at 80 bytes gives 10 ms per frame. G.711 at 240 bytes gives 30 ms per frame.

• FP—Frames per packet. Number of codec speech frames encapsulated into a single Real-time Transport Protocol (RTP) packet. Typical values are 1, 2, and 3. Packing lower number of frames per packet results in lower efficiency of IP bandwidth usage. The tradeoff is lower delays and higher robustness of the network.

• VS—Voice Activity Detection (VAD)-enabled flag. VAD is enabled when VS has a value of one. It results in compression of silent periods leading to reduced or zero packets per second. VAD is disabled when VS has a value of zero. It results in the transmission of continuous packets per second irrespective of active or silent periods on the transmission path.

• GT—Transmission gain factor (linear). Digital gain multiplier applied to the transmission on the signal path from the PSTN toward the network. GT is applied at the echo canceller Sout port. A gain factor of less than one indicates a loss pad.

• GR—Reception gain factor (linear). Digital gain multiplier applied to reception on the signal path from the network toward the PSTN. GR is applied at the echo canceller Rin port. A gain factor of less than one indicates a loss pad.

• JD—Jitter buffer mode. It consists of the following modes:

  • Adaptive mode = 1
  • Fixed mode (no timestamps) = 2
  • Fixed mode (with timestamps) = 3
  • Fixed mode (with passthrough) = 4

• JN—Jitter buffer nominal playout delay. Size of the jitter buffer in milliseconds. An adaptive jitter buffer tries to make the playout delay equal to the nominal (desired) delay when the observed jitter is small enough to allow this adjustment. For a fixed-mode jitter buffer, the nominal setting is the constant playout delay itself.

• JM—Minimum playout delay. Minimum playout delay setting for an adaptive-mode jitter buffer. The playout delay never goes below the minimum playout setting even if the observed jitter is zero. This setting is not used for a fixed-mode jitter buffer because the playout delay is fixed and constant at the nominal setting.

• JX—Maximum playout delay. Sets the limit for increasing the playout delay of an adaptive-mode jitter buffer. An adaptive buffer increases when the jitter is higher than the instantaneous playout delay value.

K-factor is an endpoint mean opinion score (MOS) estimation algorithm defined in the ITU standard P.VTQ. It is a general estimator of the mean value of a perceptual evaluation of speech quality (PESQ) population for a specific impairment pattern.

The ITU standard P.862 defines and describes the PESQ as an objective method for end-to-end speech quality assessment of narrow band telephone networks and speech codecs.

Mean opinion score (MOS) is associated with the output of a well-designed listening experiment. All MOS experiments use a five-point PESQ scale as defined in the ITU standard P.862.1. The MOS estimate is inversely proportional to frame loss density. Clarity decreases as more frames are lost or discarded at the receiving end.

K-factor represents a weighted estimate of average user annoyance due to distortions caused by effective packet loss such as dropouts and warbles. It does not estimate the impact of delay-related impairments such as echo. It is an estimate of listening quality (MOS-LQO) rather than conversational quality (MOS-CQO), and measurements of average user annoyance range from 1 (poor voice quality) to 5 (very good voice quality).

K-factor is trained or conditioned by speech samples from numerous speech databases, where each training sentence or network condition associated with a P.862.1 value has a duration of eight seconds. For more accurate scores, K-factor estimates are generated for every 8 seconds of active speech.

K-factor and other MOS estimators are considered to be secondary or derived statistics because they warn a network operator of frame loss only after the problem becomes significant. Packet counts, concealment ratios, and concealment second counters are primary statistics because they alert the network operator before network impairment has an audible impact or is visible through MOS.

• KF—K-factor MOS-LQO estimate (instantaneous). Estimate of the MOS score of the last 8 seconds of speech on the reception signal path. If VAD is active, the MOS calculation is suspended during periods of received silence to avoid inflation of MOS scores for calls with higher silence fractions.

• AV—Average K-factor score. Running average of scores observed since the beginning of a call.

• MI—Minimum K-factor score. Minimum score observed since the beginning of a call, and represents the worst sounding 8-second interval.

• BS—Baseline (maximum) K-factor score. K-factor score that can be obtained for the defined codec.

• NB—Number of bursts. Number of burst loss events after a call is started. A burst loss is a contiguous run of concealment events of length greater than one.

• FL—Average frame loss count. Total number of frame losses and concealment events observed after starting a call. The ratio of FL/NB provides the mean burst length in frames. The total concealment duration of the call is provided by the parameter DSP/CS: CT.

• NW—Number of windows. Total number of K-factor windows observed after starting a call. The number of windows is directly proportional to the duration of a call.

• VR—Version ID. Version number that identifies a specific K-factor MOS score.

DSP/CS measures packet (frame) loss and its effect on voice quality in an impaired network. The parameters for concealment statistics are as follows:

• CR—Concealment ratio (instantaneous). An interval-based average concealment rate, and is the ratio of concealment time over speech time for the last 3 seconds of active speech. When VAD is enabled, calculation of the concealment ratio is suspended during periods of speech silence. During this suspension, it may take more than 3 seconds for a new value to be generated.

• AV—Average CR. Average of all CR reports after starting a call.

• MX—Maximum CR. The maximum concealment ratio observed after starting a call.

• CS—Concealed time. The duration of time in seconds during which some concealment is observed.

• CT—Total concealment time. The total duration of time in milliseconds during which concealment is observed after starting a call.

• TT—Total speech time. The duration of time in milliseconds during which active speech is observed after starting a call.

• OK—Ok time. The duration of time in seconds during which no concealment is observed.

• SC—Severely concealed time. The duration of time in seconds during which a significant amount of concealment is observed. If the concealment observed is usually greater than 50 milliseconds or approximately five percent, it is possible that the speech is not very audible.

• TS—Concealment threshold. The threshold in milliseconds used to determine a second as severely concealed. The threshold for concealed seconds is 0 milliseconds, and for severely concealed seconds is 50 milliseconds.

The R-factor helps in planning voice transmission. In ITU standards G.107 and G.113, the R-factor is defined as follows:

R = Ro - Is - Id - Ie-eff + A

The parameters for the R-Factor are as follows:

• Ro is based on the signal-to-noise ratio.

• Is is the simultaneous impairment factor and includes the overall loudness rating.

• Id is the delay impairment factor and includes talker (Idte) and listener (Idle) echos, and delays (Idd).

• Ie-eff is the equipment impairment factor and includes packet losses and the types of codecs.

• A is the advantage factor.

• ML—R-factor MOS listening quality objective. It reflects only packet loss and codec-related impairments and does not include delay effects.

• MC—R-factor MOS-CQE.

• R1—R-factor LQ profile 1.

• R2—R-factor LQ profile 2.

• IF—Effective codec impairment (Ie_eff).

• ID—Idd.

• IE—Codec baseline score (Ie). The tabulated baseline codec impairment factor.

• BL—Codec baseline (Bpl). The packet loss robustness factor for the codec being used.

• R0—R0 (default). The nominal value at which the signal-to-noise ratio is considered nominal.

The parameters for user concealment are as follows:

• U1—User concealment seconds 1 count (UCS1)

• U2—User concealment seconds 2 count (UCS2)

• T1—UCS1 threshold in milliseconds

• T2—UCS2 threshold in milliseconds

The parameters for delay statistics are as follows:

• RT—Round trip delay

• ED—End system delay