"RFC 2833 RTP Event" Consecutive Events and the E "End" Bit
- by brian_d
Hello,
I can send out a RFC 2833 dtmf event as outlined at http://www.ietf.org/rfc/rfc2833.txt
When I do set the E "End" bit, but leave it as 0, I get the following behaviour:
If for example keys 7874556332111111145855885#3 were pressed, then ALL events would be sent and show up in a program like wireshark, however only 87456321458585#3 would sound.
So the first key (which I figure could be a separate issue) and any repeats of an event (ie 11111) are failing to sound.
In section 3.9, figure 2 of the above linked document, they give a 911 example. Here all but the last event have the E bit set.
When I set the bit for all numbers, I never get an event to sound.
I have thought of a couple possible thing but do not know if they are the reason:
1) figure 2 shows payload types of 96 and 97 sent. I have not nor know how to exactly. In section 3.8, codes 96 and 97 are described as "the dynamic payload types 96 and 97 have been assigned for the redundancy mechanism and the telephone event payload respectively"
2) In section 3.5, "E:", "A sender MAY delay setting the end bit until retransmitting the last packet for a tone, rather than on its first transmission" Does anyone have an idea of how to actually do this?
I have also fiddled around with timestamp intervals and the RTP marker.
Any help is greatly appreciated. Here is a sample wireshark event capture of the relevant areas:
6590 31.159045000 xx.x.x.xxx --.--.---.-- RTP EVENT Payload type=RTP Event, DTMF Pound # (end)
Real-Time Transport Protocol
Stream setup by SDP (frame 6225)
Setup frame: 6225
Setup Method: SDP
10.. .... = Version: RFC 1889 Version (2)
..0. .... = Padding: False
...0 .... = Extension: False
.... 0000 = Contributing source identifiers count: 0
0... .... = Marker: False
Payload type: telephone-event (101)
Sequence number: 0
Extended sequence number: 65536
Timestamp: 0
Synchronization Source identifier: 0x15f27104 (368210180)
RFC 2833 RTP Event
Event ID: DTMF Pound # (11)
1... .... = End of Event: True
.0.. .... = Reserved: False
..00 0000 = Volume: 0
Event Duration: 2048
