[Cast] Limit frames in flight by duration, and not by number of frames.

media/cast/sender/audio_sender.cc

Index: media/cast/sender/audio_sender.cc
diff --git a/media/cast/sender/audio_sender.cc b/media/cast/sender/audio_sender.cc
index e79be079ce5e7dc8756d34b3aa39101a646fc98f..6c988d9722441bb061fafac07b46c3a284e7dec8 100644
--- a/media/cast/sender/audio_sender.cc
+++ b/media/cast/sender/audio_sender.cc
@@ -4,6 +4,8 @@
 
 #include "media/cast/sender/audio_sender.h"
 
+#include <algorithm>
+
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
@@ -61,9 +63,6 @@ AudioSender::AudioSender(scoped_refptr<CastEnvironment> cast_environment,
   transport_config.ssrc = audio_config.ssrc;
   transport_config.feedback_ssrc = audio_config.incoming_feedback_ssrc;
   transport_config.rtp_payload_type = audio_config.rtp_payload_type;
-  // TODO(miu): AudioSender needs to be like VideoSender in providing an upper
-  // limit on the number of in-flight frames.
-  transport_config.stored_frames = max_unacked_frames_;
   transport_config.aes_key = audio_config.aes_key;
   transport_config.aes_iv_mask = audio_config.aes_iv_mask;
 
@@ -86,25 +85,40 @@ void AudioSender::InsertAudio(scoped_ptr<AudioBus> audio_bus,
   }
   DCHECK(audio_encoder_.get()) << "Invalid internal state";
 
-  // TODO(miu): An |audio_bus| that represents more duration than a single
-  // frame's duration can defeat our logic here, causing too much data to become
-  // enqueued.  This will be addressed in a soon-upcoming change.
-  if (ShouldDropNextFrame(recorded_time)) {
-    VLOG(1) << "Dropping frame due to too many frames currently in-flight.";
+  // Check that enqueuing the samples in |audio_bus| won't cause more frames to
+  // become in-flight than the system's design limit.
+  const int count_unacked_frames = GetUnackedFrameCount();
+  const int64 samples_unacked =
+      count_unacked_frames * audio_encoder_->GetSamplesPerFrame();
+  const int64 samples_would_be_in_flight =
+      samples_unacked + samples_in_encoder_ + audio_bus->frames();
+  const int frames_would_be_in_flight =
+      samples_would_be_in_flight / audio_encoder_->GetSamplesPerFrame();
+  if (frames_would_be_in_flight > kMaxUnackedFrames) {
+    VLOG(1) << "Dropping audio: Too many frames would be in-flight.";
     return;
   }
 
-  samples_in_encoder_ += audio_bus->frames();
+  // Check that enqueuing the samples in |audio_bus| won't exceed the allowed
+  // in-flight media duration.
+  const int64 max_samples_in_flight =
+      TimeDeltaToRtpDelta(GetAllowedInFlightMediaDuration(), rtp_timebase());
+  VLOG(2) << "Audio samples in-flight: "
+          << samples_unacked << " unacked + "
+          << samples_in_encoder_ << " in encoder + "
+          << audio_bus->frames() << " additional would be "
+          << (max_samples_in_flight > 0 ?
+                  100 * samples_would_be_in_flight / max_samples_in_flight :
+                  kint64max) << "% of allowed in-flight.";
+  if (samples_would_be_in_flight > max_samples_in_flight) {
+    VLOG(1) << "Dropping audio: Too long an audio duration would be in-flight.";
+    return;
+  }
 
+  samples_in_encoder_ += audio_bus->frames();
   audio_encoder_->InsertAudio(audio_bus.Pass(), recorded_time);
 }
 
-int AudioSender::GetNumberOfFramesInEncoder() const {
-  // Note: It's possible for a partial frame to be in the encoder, but returning
-  // the floor() is good enough for the "design limit" check in FrameSender.
-  return samples_in_encoder_ / audio_encoder_->GetSamplesPerFrame();
-}
-
 void AudioSender::OnAck(uint32 frame_id) {
 }