Stop source and fire MediaStreamTrack ended event if missing audio input callbacks are detected.

media/audio/mac/audio_low_latency_input_mac.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 #include "media/audio/mac/audio_low_latency_input_mac.h"
 
 #include <CoreServices/CoreServices.h>
 #include <mach/mach.h>
 #include <string>
 
 #include "base/bind.h"
@@ skipping 18 matching lines @@
 // The stream will be stopped as soon as this time limit is passed.
 const int kMaxErrorTimeoutInSeconds = 1;
 
 // A repeating timer is created and started in Start() and it triggers calls
 // to CheckIfInputStreamIsAlive() where we do periodic checks to see if the
 // input data callback sequence is active or not. If the stream seems dead,
 // up to |kMaxNumberOfRestartAttempts| restart attempts tries to bring the
 // stream back to life.
 const int kCheckInputIsAliveTimeInSeconds = 5;
 
-// Number of restart indications required to actually trigger a restart
-// attempt.
-const int kNumberOfIndicationsToTriggerRestart = 1;
+// Number of restart indications required to trigger a restart after a
+// successful start.
+const int kIndicationsToTriggerRestartAfterSuccessfulStart = 2;
 
 // Max number of times we try to restart a stream when it has been categorized
 // as dead. Note that we can do many restarts during an audio session and this
 // limitation is per detected problem. Once a restart has succeeded, a new
 // sequence of |kMaxNumberOfRestartAttempts| number of restart attempts can be
 // done.
 const int kMaxNumberOfRestartAttempts = 1;
 
 // A one-shot timer is created and started in Start() and it triggers
 // CheckInputStartupSuccess() after this amount of time. UMA stats marked
@@ skipping 1213 matching lines @@
   // A non-zero value of this counter is a strong indication of a "dead" input
   // stream. Reset the same counter if the stream is alive.
   if (time_since_last_callback.InSecondsF() >
       0.5 * kCheckInputIsAliveTimeInSeconds) {
     ++number_of_restart_indications_;
   } else {
     number_of_restart_indications_ = 0;
   }
 
   // Restart the audio stream if two conditions are met. First, the number of
-  // restart indicators must be larger than a threshold, and secondly, only a
+  // restart indicators must reach a threshold, and secondly, only a
   // fixed number of restart attempts is allowed.
   // Note that, the threshold is different depending on if the stream is seen
   // as dead directly at the first call to Start() (i.e. it has never started)
   // or if the stream has started OK at least once but then stopped for some
   // reason (e.g by placing the device in sleep mode). One restart indication
   // is sufficient for the first case (threshold is zero), while a larger value
-  // (threshold > 0) is required for the second case to avoid false alarms when
+  // (threshold > 1) is required for the second case to avoid false alarms when
   // e.g. resuming from a suspended state.
-  const size_t restart_threshold =
-      GetInputCallbackIsActive() ? kNumberOfIndicationsToTriggerRestart : 0;
-  if (number_of_restart_indications_ > restart_threshold &&
+  const size_t indications_to_trigger_restart =
+      GetInputCallbackIsActive()
+          ? kIndicationsToTriggerRestartAfterSuccessfulStart
+          : 1;
+  DCHECK_LE(number_of_restart_indications_, indications_to_trigger_restart);
+  if (number_of_restart_indications_ == indications_to_trigger_restart &&

[ossu-chromium, 2017/05/22 11:27:35]

So, this is functionally equivalent but rephrased to be a bit simpler to read?

[Henrik Grunell, 2017/05/22 15:04:54]

Yes, exactly. I hope you agree it is. :o

       number_of_restart_attempts_ < kMaxNumberOfRestartAttempts) {
     SetInputCallbackIsActive(false);
     ++total_number_of_restart_attempts_;
     ++number_of_restart_attempts_;
     number_of_restart_indications_ = 0;
     RestartAudio();
   }
 }
 
 void AUAudioInputStream::CloseAudioUnit() {
@@ skipping 371 matching lines @@
 
   number_of_frames_provided_ = 0;
   glitches_detected_ = 0;
   last_sample_time_ = 0;
   last_number_of_frames_ = 0;
   total_lost_frames_ = 0;
   largest_glitch_frames_ = 0;
 }
 
 }  // namespace media