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 343 matching lines @@
 }
 
 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)) {
+  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);
@@ skipping 1845 matching lines @@
   if (_rtpRtcpModule->SendTelephoneEventOutband(
       event, duration_ms, kTelephoneEventAttenuationdB) != 0) {
     _engineStatisticsPtr->SetLastError(
         VE_SEND_DTMF_FAILED, kTraceWarning,
         "SendTelephoneEventOutband() failed to send event");
     return -1;
   }
   return 0;
 }
 
-int Channel::SetSendTelephoneEventPayloadType(unsigned char type) {
+int Channel::SetSendTelephoneEventPayloadType(int payload_type) {
   WEBRTC_TRACE(kTraceInfo, kTraceVoice, VoEId(_instanceId, _channelId),
                "Channel::SetSendTelephoneEventPayloadType()");
-  if (type > 127) {
-    _engineStatisticsPtr->SetLastError(
-        VE_INVALID_ARGUMENT, kTraceError,
-        "SetSendTelephoneEventPayloadType() invalid type");
-    return -1;
-  }
-  CodecInst codec = {};
+  RTC_DCHECK_LE(0, payload_type);
+  RTC_DCHECK_GE(127, payload_type);
+  CodecInst codec = {0};
   codec.plfreq = 8000;
-  codec.pltype = type;
+  codec.pltype = payload_type;
   memcpy(codec.plname, "telephone-event", 16);
   if (_rtpRtcpModule->RegisterSendPayload(codec) != 0) {
     _rtpRtcpModule->DeRegisterSendPayload(codec.pltype);
     if (_rtpRtcpModule->RegisterSendPayload(codec) != 0) {
       _engineStatisticsPtr->SetLastError(
           VE_RTP_RTCP_MODULE_ERROR, kTraceError,
           "SetSendTelephoneEventPayloadType() failed to register send"
           "payload type");
       return -1;
     }
@@ skipping 1307 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