Early initialize recording on the ADM from WebRtcVoiceMediaChannel.

webrtc/media/engine/webrtcvoiceengine.cc

 /*
  *  Copyright (c) 2004 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 1060 matching lines @@
     return;
   }
   LOG_RTCERR0(StopRtcEventLog);
 }
 
 int WebRtcVoiceEngine::CreateVoEChannel() {
   RTC_DCHECK(worker_thread_checker_.CalledOnValidThread());
   return voe_wrapper_->base()->CreateChannel(voe_config_);
 }
 
+webrtc::AudioDeviceModule* WebRtcVoiceEngine::adm() {
+  RTC_DCHECK(worker_thread_checker_.CalledOnValidThread());
+  RTC_DCHECK(adm_);
+  return adm_;
+}
+
 class WebRtcVoiceMediaChannel::WebRtcAudioSendStream
     : public AudioSource::Sink {
  public:
   WebRtcAudioSendStream(int ch, webrtc::AudioTransport* voe_audio_transport,
                         uint32_t ssrc, const std::string& c_name,
                         const std::vector<webrtc::RtpExtension>& extensions,
                         webrtc::Call* call)
       : voe_audio_transport_(voe_audio_transport),
         call_(call),
         config_(nullptr) {
@@ skipping 702 matching lines @@
   playout_ = playout;
   return true;
 }
 
 void WebRtcVoiceMediaChannel::SetSend(bool send) {
   TRACE_EVENT0("webrtc", "WebRtcVoiceMediaChannel::SetSend");
   if (send_ == send) {
     return;
   }
 
-  // Apply channel specific options when channel is enabled for sending.
+  // Apply channel specific options, and initialize the ADM for recording (this
+  // may take time on some platforms, e.g. Android).
   if (send) {
     engine()->ApplyOptions(options_);
+
+    // InitRecording() will return an error if the ADM is already recording.
+    if (!engine()->adm()->Recording()) {

[Taylor Brandstetter, 2016/04/01 18:41:02]

Shouldn't this call "RecordingIsInitialized"?

[the sun, 2016/04/01 21:35:40]

Actually, it looks like both must be checked. Looking at the various ADM
implementations of InitRecording(), most will return -1 if we're already
recording, but 0 if we're already initialized (see e.g.
audio_device_alsa_linux.cc, audio_device_mac.cc, audio_device_core_win.cc). But
looking closer at the Android and iOS implementations (audio_record_jni.cc,
WebRtcAudioRecord.java, audio_device_ios.mm), those will instead DCHECK that the
device is neither recording nor initialized for recording.

+      if (engine()->adm()->InitRecording() != 0) {
+        LOG(LS_WARNING) << "Failed to initialize recording";
+      }
+    }
   }
 
   // Change the settings on each send channel.
   for (auto& kv : send_streams_) {
     kv.second->SetSend(send);
   }
 
   send_ = send;
 }
 
@@ skipping 676 matching lines @@
     }
   } else {
     LOG(LS_INFO) << "Stopping playout for channel #" << channel;
     engine()->voe()->base()->StopPlayout(channel);
   }
   return true;
 }
 }  // namespace cricket
 
 #endif  // HAVE_WEBRTC_VOICE