Hi all,
I've started looking at the code stipus provided to detect inband DTMF
(http://list.sipfoundry.org/archive/sipxtapi-dev/msg01507.html). His version is
based on an older version of sipxmedialib, i.e. where MpConnection is still in
one piece. In the meantime, MpConnection has been split up into at least two
classes, and several other changes have been made to the design. A few
questions have arisen when figuring out what would be the best way to
accomplish this:
Who should handle the detection of inband dtmf? In Stipus' version, a separate
class (MprDecodeInBandDtmf) takes care of it, it is instantiated inside
MpConnection and added to the resource chain after MprDecode (res =
pParent->addLink(*mpDecode, 0, *mpDecodeInBandDtmf, 0); in the old version). I
would assume that in the new version, the correct place would now be
MpRtpInputAudioConnection, am I correct?
When should the detection take place? As stated above, in the old version the
inband detection was added to the resource chain inside MpConnection, but the
internals of MpRtpInputAudioConnection are no longer added to the resource
chain - MpRtpInputAudioConnection is itself added to the resource chain in
MpCallFlowGraph, but that's as far as it goes. Therefore the next question
becomes: where should the detection take place? should
MpRtpInputAudioConnection call MprDecodeInBandDtmf::doProcessFrame inside
MpRtpInputAudioConnection::processFrame, should perhaps MprDecode handle this,
or should some entirely other mechanism be used?
A notification about the DTMF code must be passed upwards when detected, and in
Stipus version he uses the mpFlowGraph variable defined inside MpResource - but
that variable isn't necessarily initialized, and MpRtpInputAudioConnection
doesn't seem to know about the flow graph, hence it probably won't be able to
tell MprDecodeInBandDtmf about the flowgraph etc. So the third question is:
what is the preferred way to accomplish this? As I understood then some rewrite
of the messaging framework was in the pipeline, but I simply don't remember
what the status on that is.
I think that would be all for now, I do hope that I will succeed in
incorporating this functionality into the codebase, in which case I would
provide a patch for others interested.
Regards,
Daníel
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