Transcoder Resources

A transcoder device takes the output stream of one codec and converts the voice streams to another compression type. For example, a transcoder can take an output stream from a G.711 codec and convert it to a G.729 stream. Depending on the hardware resources you are using, transcoders for Cisco CallManager convert between G.711, G.723, G.729, and GSM codecs. A transcoder device provides additional capabilities and can be used to enable supplementary services for H.323 endpoints.

Figure 15-4 shows a transcoder device (XCODE) enabling communication between two different codecs and providing MTP services for H.323 endpoints.

Figure 15-4. Transcoder Operation

The Cisco CallManager invokes a transcoder on behalf of endpoint devices when the two devices use different voice codecs and would normally not be able to communicate. When inserted into a call, the transcoder converts the data streams between the two incompatible codecs to enable communications between them. The transcoder remains invisible to either the user or the endpoints that are involved in a call. For example, a user could be communicating across the IP WAN using the G.729 codec to a legacy voice-mail server supporting only G.711. Cisco CallManager can invoke transcoding resources to convert between the codecs and allow communication to occur.

Note

Because of the amount of resources necessary to perform transcoding, Cisco CallManager servers cannot be used as transcoding resources.

Table 15-6 shows the currently available transcoding resources and the resource capabilities of each.

Table 15-6. Transcoder Resource Capabilities

Resource	From Codec	To Codec
WS-X6608-T1, WS-X6608-E1	G.723. G.729a, GSM FR, GSM EFR	G.711 a-law or mu-law
	G.711 a-law or mu-law	G.723. G.729a, GSM FR, GSM EFR
NM-HDV and NM-HDV-FARM	G.729, G.729a, G.729b, G.729ab	G.711 a-law or mu-law
	G.711 mu-law	G.729, G.729a, G.729b, G.729ab
NM-HD and NM-HDV2	G.729, G.729a, G.729b, G.729ab, GSM FR, GSM EFR	G.711 a-law or mu-law
	G.711 a-law or mu-law	G.729, G.729a, G.729b, G.729ab, GSM FR, GSM EFR
WS-SVC-CMM	This type provides transcoding between any combination of the following codecs: G.711 a-law and G.711 mu-law G.729 annex A and annex B G.723.1 GSM (FR)

Note

Cisco is continually adding transcoding-capable devices to their product line. For the latest information on transcoding resources, check the Cisco website.

 

Transcoder Configuration

To configure or add a new transcoder, choose Service > Media Resource > Transcoder, click Add a New Transcoder (shown in Figure 15-5), and then follow this general procedure:

Step 1.	Choose the appropriate transcoder type: Cisco Media Termination Point Hardware, Cisco IOS Media Termination Point, Cisco IOS Enhanced Media Termination Point, or Cisco Media Termination Point (WS-SVC-CMM).
Step 2.	For Cisco Media Termination Point Hardware or Cisco Media Termination Point (WS-SVC-CMM), enter a MAC address, which must be 12 characters.
Step 3.	For Cisco Media Termination Point (WS-SVC-CMM) transcoders, choose a subunit from the drop-down list (not shown in the figure).
Step 4.	Choose a device pool. For more detailed information on the chosen device pool, click View Details.
Step 5.	Enter any special load information into the Special Load Information field or leave it blank to use the default. Valid characters include letters, numbers, dashes, dots (periods), and underscores.
Step 6.	For Cisco Media Termination Point (WS-SVC-CMM) transcoders, choose a maximum capacity from the drop-down list (not shown in the figure).

Figure 15-5. Transcoder Configuration Window

Note

The preceding procedure shows the CallManager transcoder configuration for the WS-SVC-CMM module. The configuration fields for each type of transcoding resource are unique.