Multi frequency DTMF support - receiver side

webrtc/media/engine/payload_type_mapper.cc

Index: webrtc/media/engine/payload_type_mapper.cc
diff --git a/webrtc/media/engine/payload_type_mapper.cc b/webrtc/media/engine/payload_type_mapper.cc
index 87b54be33b51f530e0aac15da859d614bba7eedd..f58e5f890982055fbcce756ed027c25d9c205ffc 100644
--- a/webrtc/media/engine/payload_type_mapper.cc
+++ b/webrtc/media/engine/payload_type_mapper.cc
@@ -84,6 +84,9 @@ PayloadTypeMapper::PayloadTypeMapper()
               {{"minptime", "10"}, {"useinbandfec", "1"}}}, 111},
           {{kRedCodecName,    90000, 0}, kDefaultRedPlType},
           {{kUlpfecCodecName, 90000, 0}, kDefaultUlpfecType},
+          {{kDtmfCodecName,   48000, 1}, 123},

[ossu, 2016/10/04 09:26:56]

I'm not sure these need to be added here, but maybe it's as well. Since they're
new, they're not necessary to ensure backwards compatibility. Could be nice that
they match the numbers in kCodecPrefs, although outer layers will ensure this
gets sorted out regardless.

[the sun, 2016/10/08 22:06:51]

If they're not there, we may map the PTs differently between send and receive,
which AFAIK isn't supported in the signaling layer yet - or did you fix that?

[ossu, 2016/10/10 23:26:34]

I believe that'll be handled by the PeerConnection layer (my spidey-sense tells
me that mediasession.cc might be involved but I can look into it). At one point,
the send and receive lists will be joined and that's done the same way as the
offer and answer lists are joined. With that, a single payload type is picked
for identical formats.

[the sun, 2016/10/11 19:17:17]

Because you gave the lgtm, I guess you still think it is right to leave the
"static" mapping in here though?

[ossu, 2016/10/11 20:17:26]

Yes, I've no strong feelings either way. It's probably safer to keep them
statically here, for now. We can deal with getting rid of all of these static
dynamic mappings at once, at a later time.

+          {{kDtmfCodecName,   32000, 1}, 124},
+          {{kDtmfCodecName,   16000, 1}, 125},
           {{kDtmfCodecName,    8000, 1}, 126}}) {
   // TODO(ossu): Try to keep this as change-proof as possible until we're able
   // to remove the payload type constants from everywhere in the code.