GVP MCP:mpc:amr-fmtp

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Published Option

amr.fmtp

Default Value: octet-align=0 | octet-align=1
Valid Values: <parameter=value>[|<parameter=value>]*
Changes Take Effect: At start/restart

Specifies the AMR SDP RTP payload configurations offered and accepted by the MCP. Set to one or more fmtp text values separated by the '|' character. The fmtp text is the same as would appear in the SDP negotiation (see RFC 4867). Each "|" separated value configures an AMR payload type. There are two fmtp parameters that can be set for each payload type, octet-align and mode-set.

Setting octet-align=0 or octet-align=1 disables or enables octet align mode for the payload.

Setting mode-set restricts the AMR modes for the payload. For example, setting "mode-set=0,1" only allows modes 0 and 1. If mode-set is not set, all modes are allowed unless the mode-set is restricted by the remote end. Valid modes are inclusively 0 to 7.

For example, setting this parameter to "octet-align=1" enables one payload type with octet aligned mode enabled and any mode allowed, and setting it to "octet-align=0 | octet-align=1" enables two payload types, one with bandwidth efficient mode enabled and any mode allowed, and one with octet aligned enabled and any mode allowed.

Note, the mode-set parameter can cause transcoding to be required. For example, if a prompt to be played is in AMR format mode 5, but only mode 0 is allowed in the payload, a transcoder will be invoked to transcode from AMR mode 5 to AMR mode 0.

Some AMR implementations may specify a fmtp options that are not actually activated for the payload. To work around this, the mpc.amr.fmtp can be set to "*". For this setting, all fmtp content in an SDP offer will be ignored and "octet-align=0" will be returned in the SDP answer. Similarly, an offer for this configuration will be set to "octet-align=0", and all fmtp content in the answer will be ignored.

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