Relanding https://codereview.webrtc.org/1715883002/ in pieces.

webrtc/voice_engine/channel.cc

 /*
  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 342 matching lines @@
   return true;
 }
 
 void Channel::OnPlayTelephoneEvent(uint8_t event,
                                    uint16_t lengthMs,
                                    uint8_t volume) {
   WEBRTC_TRACE(kTraceStream, kTraceVoice, VoEId(_instanceId, _channelId),
                "Channel::OnPlayTelephoneEvent(event=%u, lengthMs=%u,"
                " volume=%u)",
                event, lengthMs, volume);
-
-  if (!_playOutbandDtmfEvent || event > 15) {
-    // Ignore callback since feedback is disabled or event is not a
-    // Dtmf tone event.
-    return;
-  }
-
-  assert(_outputMixerPtr != NULL);
-
-  // Start playing out the Dtmf tone (if playout is enabled).
-  // Reduce length of tone with 80ms to the reduce risk of echo.
-  _outputMixerPtr->PlayDtmfTone(event, lengthMs - 80, volume);
 }
 
 void Channel::OnIncomingSSRCChanged(uint32_t ssrc) {
   WEBRTC_TRACE(kTraceInfo, kTraceVoice, VoEId(_instanceId, _channelId),
                "Channel::OnIncomingSSRCChanged(SSRC=%d)", ssrc);
 
   // Update ssrc so that NTP for AV sync can be updated.
   _rtpRtcpModule->SetRemoteSSRC(ssrc);
 }
 
@@ skipping 399 matching lines @@
       _transportPtr(NULL),
       _rxVadObserverPtr(NULL),
       _oldVadDecision(-1),
       _sendFrameType(0),
       _externalMixing(false),
       _mixFileWithMicrophone(false),
       _mute(false),
       _panLeft(1.0f),
       _panRight(1.0f),
       _outputGain(1.0f),
-      _playOutbandDtmfEvent(false),
       _lastLocalTimeStamp(0),
       _lastPayloadType(0),
       _includeAudioLevelIndication(false),
       _outputSpeechType(AudioFrame::kNormalSpeech),
       _average_jitter_buffer_delay_us(0),
       _previousTimestamp(0),
       _recPacketDelayMs(20),
       _RxVadDetection(false),
       _rxAgcIsEnabled(false),
       _rxNsIsEnabled(false),
@@ skipping 1403 matching lines @@
   WEBRTC_TRACE(kTraceInfo, kTraceVoice, VoEId(_instanceId, _channelId),
                "Channel::SendTelephoneEventOutband(...)");
   RTC_DCHECK_LE(0, event);
   RTC_DCHECK_GE(255, event);
   RTC_DCHECK_LE(0, duration_ms);
   RTC_DCHECK_GE(65535, duration_ms);
   if (!Sending()) {
     return -1;
   }
 
-  _playOutbandDtmfEvent = false;
-
   if (_rtpRtcpModule->SendTelephoneEventOutband(
       event, duration_ms, kTelephoneEventAttenuationdB) != 0) {
     _engineStatisticsPtr->SetLastError(
         VE_SEND_DTMF_FAILED, kTraceWarning,
         "SendTelephoneEventOutband() failed to send event");
     return -1;
   }
   return 0;
 }
 
@@ skipping 1325 matching lines @@
   int64_t min_rtt = 0;
   if (_rtpRtcpModule->RTT(remoteSSRC, &rtt, &avg_rtt, &min_rtt, &max_rtt) !=
       0) {
     return 0;
   }
   return rtt;
 }
 
 }  // namespace voe
 }  // namespace webrtc