Codec-based thresholds supplement performance thresholds to help you better understand and manage call quality. By default, codec thresholds apply codec-appropriate values for MOS and Network MOS as traffic using various standard codecs is detected. These values can be changed, however. The administrator sets these thresholds relative to codec performance or relative to absolute MOS.
A codec encodes and decodes the audio from both ends of a telephone conversation, producing packets that are sent and received across the network. Codec performance has a noticeable effect on VoIP and video performance.
Many codecs are available to optimize VoIP or video performance, each with an accompanying set of drawbacks and benefits. In addition to the different bandwidth requirements associated with different codec types, codecs have other characteristics that can affect network performance. Some high-performance codecs do not compress data and, as a result, use more bandwidth than codecs that use a compression scheme. Compression often degrades the audio signal and adds delay.
For the most part, codecs provide a certain level of audio quality, which is expressed as a theoretical maximum MOS. Some codecs from Microsoft, however, receive ratings for two types of theoretical maximum MOS, and advertise different performance expectations in wideband and narrowband environments.
UC Monitor defines thresholds for the most common codecs. An administrator can modify these values to suit specific monitoring needs. The administrator can add new codec thresholds that are based on a list of supported codecs. The settings consist of Degraded and Excessive values for each MOS metric.
Predefined thresholds are available for most popular codecs, but no default codec threshold is defined. Therefore, when codec thresholds are enabled, UC Monitor applies the thresholds to the codecs it detects during monitoring. These thresholds include predefined or custom thresholds that use the codecs that are detected from monitored call traffic.
For codecs that are not in the list of predefined or custom codec thresholds, the associated MOS appears as Unrated in reports.
Note: The proprietary Microsoft codecs, RTAudio and Siren, offer a threshold for Network MOS, a metric that is available from Microsoft VoIP and video endpoints. The MOS scale used in the Microsoft codecs is different from the scale that other codecs use. For example, the MOS for a Degraded threshold for the RTAudio codec does not represent equivalent performance to the same threshold for the G.729 codec.
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