Injectable audio encoders: WebRtcVoiceEngine and company

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 1285 matching lines @@
     _rtpRtcpModule->DeRegisterSendPayload(payload_type);
     if (_rtpRtcpModule->RegisterSendPayload(lies) != 0) {
       WEBRTC_TRACE(
           kTraceError, kTraceVoice, VoEId(_instanceId, _channelId),
           "SetEncoder() failed to register codec to RTP/RTCP module");
       return false;
     }
   }
 
   audio_coding_->SetEncoder(std::move(encoder));
+  codec_manager_.UnsetCodecInst();
   return true;
 }
 
+void Channel::ModifyEncoder(
+    rtc::FunctionView<void(std::unique_ptr<AudioEncoder>*)> modifier) {
+  audio_coding_->ModifyEncoder(modifier);
+}
+
 int32_t Channel::RegisterVoiceEngineObserver(VoiceEngineObserver& observer) {
   WEBRTC_TRACE(kTraceInfo, kTraceVoice, VoEId(_instanceId, _channelId),
                "Channel::RegisterVoiceEngineObserver()");
   rtc::CritScope cs(&_callbackCritSect);
 
   if (_voiceEngineObserverPtr) {
     _engineStatisticsPtr->SetLastError(
         VE_INVALID_OPERATION, kTraceError,
         "RegisterVoiceEngineObserver() observer already enabled");
     return -1;
@@ skipping 11 matching lines @@
     _engineStatisticsPtr->SetLastError(
         VE_INVALID_OPERATION, kTraceWarning,
         "DeRegisterVoiceEngineObserver() observer already disabled");
     return 0;
   }
   _voiceEngineObserverPtr = NULL;
   return 0;
 }
 
 int32_t Channel::GetSendCodec(CodecInst& codec) {
-  auto send_codec = codec_manager_.GetCodecInst();
-  if (send_codec) {
-    codec = *send_codec;
+  {

[ossu, 2017/04/26 15:45:36]

At first, I had this code just ask the ACM directly, however it turns out that
when Channel does SetSendCodec, all the codec info within the ACM is discarded,
and it's treated as just another external codec. The ACM has its own
codec_manager_ instance it (I guess) sometimes uses to create encoders.

Now, we'll use the CodecInst passed to SetSendCodec if it's available (it's set
up with PCMU as the default codec in Channel::Init), or ask the ACM for info if
it's not - since it has the ability to make something reasonable up for external
encoders.

When calling Channel::SetEncoder, it will ensure we discard any previously
configured CodecInst by calling CodecManager::UnsetCodecInst() above.

[kwiberg-webrtc, 2017/04/26 20:03:36]

Yes. Hopefully we can remove that soon-ish.
Ack.

We really need to make it a priority to remove all uses of CodecInst sooner
rather than later; this sort of code feels like it could cause much weeping and
gnashing of teeth the next time we need to change it and have to figure out how
it works...

+    const CodecInst* send_codec = codec_manager_.GetCodecInst();
+    if (send_codec) {
+      codec = *send_codec;
+      return 0;
+    }
+  }
+  rtc::Optional<CodecInst> acm_send_codec = audio_coding_->SendCodec();
+  if (acm_send_codec) {
+    codec = *acm_send_codec;
     return 0;
   }
   return -1;
 }
 
 int32_t Channel::GetRecCodec(CodecInst& codec) {
   return (audio_coding_->ReceiveCodec(&codec));
 }
 
 int32_t Channel::SetSendCodec(const CodecInst& codec) {
@@ skipping 1755 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