Codec Parameters

Use this page to modify the Frame Size (in milliseconds) and the Frames per Packet of a Codec. This option is available only for G.711 Codecs.

Notes:  

If two devices each have a Codec defined, but there are no Codecs defined in the mapping between them, then they are not allowed to communicate directly to each other. This can be used to intentionally block traffic between some Codecs.

G.726 is only available with AudioCodes.

Packet and Frame size: Summary on packet size and frequency from the www.erlang.com website: "The frequency at which the voice packets are transmitted have a significant bearing on the bandwidth required. The selection of the packet duration (and therefore the packet frequency) is a compromise between bandwidth and quality. Lower durations require more bandwidth.  However, if the duration is increased, the delay of the system increases, and it becomes more susceptible to packet loss; 20ms is a typical figure." So, the more of the voice you put in a single packet (i.e., 60ms versus 20ms), the more of the voice you lose if that packet is lost.  

MOS: The quality of transmitted speech is a subjective response of the listener. A common benchmark used to determine the quality of sound produced by specific Codecs is the mean opinion score (MOS). With MOS, a wide range of listeners judge the quality of a voice sample (corresponding to a particular Codec) on a scale of 1 (bad) to 5 (excellent). The scores are averaged to provide the MOS for that sample.