[Asterisk-Users] RFC 2833 / Timestamp

[Clif Jones]

I wasted a lot of time on this issue with an Audiocodes FXO gateway I am 
currently exploring possible
workarounds.  Of course, I would really like to see a patch on the 
asterisk-cvs mail list. :)

Gerard O'Rourke wrote:

>Hi,
>
>We are using Asterisk for a h323 / SIP converter.
>We are having problems when users enter DTMF quickly.
>
>The reason for the problem is that the Timestamp Header field in the RTP
>stream
>for the 2 separate DTMF events are set at the same number.
>
>Has anyone else had this problem and does anyone know if there is a fix for
>it?
>
>See below for trace:
>Note how the Timestamp header is set to "24352" in both cases.
>Our system ignores the first DTMF because of this.
>
>Note: Cisco uses a much larger timestamp header than this ( a 4 digit HEX
>number e.g. Timestamp: 1527784437
>And never use the same Timestamp for separate DTMF events.
>
>Rgs,
>Gerard.
>
>
>
>User Datagram Protocol, Src Port: 6934 (6934), Dst Port: 1686 (1686)
>Real-Time Transport Protocol
>    10.. .... = Version: RFC 1889 Version (2)
>    ..0. .... = Padding: False
>    ...0 .... = Extension: False
>    .... 0000 = Contributing source identifiers count: 0
>    1... .... = Marker: True
>    .110 0101 = Payload type: Unknown (101)
>    Sequence number: 33529
>    Timestamp: 24352
>    Synchronization Source identifier: 1497941844
>RFC 2833 RTP Event
>    Event ID: DTMF Two 2 (2)
>    0... .... = End of Event: False
>    .0.. .... = Reserved: False
>    ..00 1010 = Volume: 10
>    Event Duration: 0
>
>
>User Datagram Protocol, Src Port: 6934 (6934), Dst Port: 1686 (1686)
>Real-Time Transport Protocol
>    10.. .... = Version: RFC 1889 Version (2)
>    ..0. .... = Padding: False
>    ...0 .... = Extension: False
>    .... 0000 = Contributing source identifiers count: 0
>    1... .... = Marker: True
>    .110 0101 = Payload type: Unknown (101)
>    Sequence number: 33531
>    Timestamp: 24352
>    Synchronization Source identifier: 1497941844
>RFC 2833 RTP Event
>    Event ID: DTMF Three 3 (3)
>    0... .... = End of Event: False
>    .0.. .... = Reserved: False
>    ..00 1010 = Volume: 10
>    Event Duration: 0
>
>
>---------------
>Gerard O'Rourke
>Connectivity Technology Manager
>V O X P I L O T
>+353 1 209 1919
>
>
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>