ts-rtpdtmfsrc

Thread-sharing RTP DTMF (RFC 2833) source.

The ts-rtpdtmfsrc element generates RTP DTMF (RFC 2833) event packets on request from application. The application communicates the beginning and end of a DTMF event using custom upstream gstreamer events.

Compated to rtpdtmfsrc, ts-rtpdtmfsrc takes advantage of the threadshare runtime, allowing reduced number of threads and context switches when many elements are used.

To report a DTMF event, an application must send an event of type gst::event::CustomUpstream, having a structure of name "dtmf-event" with fields set according to the following table:

• type (G_TYPE_INT aka i32, 0-1): The application uses this field to specify which of the two methods specified in RFC 2833 to use. The value should be 0 for tones and 1 for named events. Tones are specified by their frequencies and events are specified by their number. This element can only take events as input. Do not confuse with "method" which specified the output.

• number (G_TYPE_INT, 0-15): The event number.

• volume (G_TYPE_INT, 0-36): This field describes the power level of the tone, expressed in dBm0 after dropping the sign. Power levels range from 0 to -63 dBm0. The range of valid DTMF is from 0 to -36 dBm0. Can be omitted if start is set to FALSE.

• start (G_TYPE_BOOLEAN aka bool, True or False): Whether the event is starting or ending.

• method (G_TYPE_INT, 1): The method used for sending event, this element will react if this field is absent or 1.

For example, the following code informs the pipeline (and in turn, the ts-rtpdtmfsrc element inside the pipeline) about the start of an RTP DTMF named event '1' of volume -25 dBm0:

 let dtmf_start_event = gst::event::CustomUpstream::builder(
     gst::Structure::builder("dtmf-event")
         .field("type", 1i32)
         .field("method", 1i32)
         .field("start", true)
         .field("number", 1i32)
         .field("volume", 25i32)
         .build(),
 )
 .build();

 pipeline.send_event(dtmf_start_event)

When a DTMF tone actually starts or stop, a "dtmf-event-processed" element GstMessage with the same fields as the "dtmf-event" GstEvent that was used to request the event. Also, if any event has not been processed when the element goes from the PAUSED to the READY state, then a "dtmf-event-dropped" message is posted on the GstBus in the order that they were received.