[asterisk-dev] [Regression issue] Garbage RTP data with Asterisk

Hans Petter Selasky hps at selasky.org
Sun Feb 8 04:24:57 CST 2015

On 02/08/15 08:45, Hans Petter Selasky wrote:
> On 02/08/15 08:44, Hans Petter Selasky wrote:
>> Hi,
>>  From time to time the Asterisk RTP engine outputs some 4-byte ULAW
>> packets (even when the data stream is ALAW), making me believe that the
>> packets don't come from the source channel driver. The content of the
>> packets is constant: 0x02 0x8A 0x02 0x80
>> These cause pops/clicks at the receiver. How can the source of these
>> packets be found? Is there perhaps a race in Asterisk?
>> Has anyone seen this issue before. I have a very old installation of
>> Asterisk ~v1.6 which does not exhibit this issue.
>> --HPS
> Forgot to mention:
> Seen with Asterisk 1.8 and 11
> --HPS


Some further investigation reveals that the payload type is "0" instead 
of "101" for DTMF.

The 4 bytes are a DMTF packet and apparently this function has failed:

>         /* Grab the payload that they expect the RFC2833 packet to be received in */
>         payload = ast_rtp_codecs_payload_code(ast_rtp_instance_get_codecs(instance), 0, AST_RTP_DTMF);


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