6.2.1 DTMF Modes

The IP media library can be used to configure which DTMF mode (in-band, RFC 2833, or out-of-band) is used by the application. The DTMF mode is set on a per-channel basis using ipm_SetParm( ) and the IPM_PARM_INFO data structure.

The eIPM_DTMFXFERMODE enumeration identifies which DTMF mode to use. The following values are supported:

• DTMFXFERMODE_INBAND - DTMF digits are sent and received in-band via standard RTP transcoding. This is the default mode when a channel is opened.
• DTMFXFERMODE_RFC2833 - DTMF digits are sent and received in the RTP stream as defined in RFC 2833.
• DTMFXFERMODE_OUTOFBAND - DTMF digits are sent and received outside the RTP stream.

Depending on the mode being used, the digit information transferred in the RTP stream.

When using RFC2833, the payload type is specified by using the following parameter/value setting in a call to ipm_SetParm( ):

• PARMCH_RFC2833_EVT_TX_PLT - Identifies the transmit payload type. The only value for this field is 101
• PARMCH_RFC2833_EVT_RX_PLT - Identifies the receive payload type. The only value for this field is 101

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