Cast: Only ACK decododable frames

Also, add an optimization to not decode frames if we are behind and multiple frames are currently decodable.

Review URL: https://codereview.chromium.org/289483003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@272709 0039d316-1c4b-4281-b951-d872f2087c98

media/cast/audio_receiver/audio_receiver.cc

@@ -169,19 +169,29 @@ void AudioReceiver::EmitAvailableEncodedFrames() {
     scoped_ptr<transport::EncodedFrame> encoded_frame(
         new transport::EncodedFrame());
     bool is_consecutively_next_frame = false;
-    if (!framer_.GetEncodedAudioFrame(encoded_frame.get(),
-                                      &is_consecutively_next_frame)) {
+    bool have_multiple_complete_frames = false;
+    if (!framer_.GetEncodedFrame(encoded_frame.get(),
+                                 &is_consecutively_next_frame,
+                                 &have_multiple_complete_frames)) {
       VLOG(1) << "Wait for more audio packets to produce a completed frame.";
       return;  // OnReceivedPayloadData() will invoke this method in the future.
     }
 
+    const base::TimeTicks now = cast_environment_->Clock()->NowTicks();
+    const base::TimeTicks playout_time =
+        GetPlayoutTime(now, encoded_frame->rtp_timestamp);
+
+    // If we have multiple decodable frames, and the current frame is
+    // too old, then skip it and decode the next frame instead.
+    if (have_multiple_complete_frames && now > playout_time) {
+      framer_.ReleaseFrame(encoded_frame->frame_id);
+      continue;
+    }
+
     // If |framer_| has a frame ready that is out of sequence, examine the
     // playout time to determine whether it's acceptable to continue, thereby
     // skipping one or more frames.  Skip if the missing frame wouldn't complete
     // playing before the start of playback of the available frame.
-    const base::TimeTicks now = cast_environment_->Clock()->NowTicks();
-    const base::TimeTicks playout_time =
-        GetPlayoutTime(now, encoded_frame->rtp_timestamp);
     if (!is_consecutively_next_frame) {
       // TODO(miu): Also account for expected decode time here?
       const base::TimeTicks earliest_possible_end_time_of_missing_frame =

media/cast/framer/cast_message_builder.cc

@@ -23,7 +23,6 @@ CastMessageBuilder::CastMessageBuilder(
       decoder_faster_than_max_frame_rate_(decoder_faster_than_max_frame_rate),
       max_unacked_frames_(max_unacked_frames),
       cast_msg_(media_ssrc),
-      waiting_for_key_frame_(true),
       slowing_down_ack_(false),
       acked_last_frame_(true),
       last_acked_frame_id_(kStartFrameId) {
@@ -32,67 +31,61 @@ CastMessageBuilder::CastMessageBuilder(
 
 CastMessageBuilder::~CastMessageBuilder() {}
 
-void CastMessageBuilder::CompleteFrameReceived(uint32 frame_id,
-                                               bool is_key_frame) {
+void CastMessageBuilder::CompleteFrameReceived(uint32 frame_id) {
+  DCHECK_GE(static_cast<int32>(frame_id - last_acked_frame_id_), 0);
+  VLOG(2) << "CompleteFrameReceived: " << frame_id;
   if (last_update_time_.is_null()) {
     // Our first update.
     last_update_time_ = clock_->NowTicks();
   }
-  if (waiting_for_key_frame_) {
-    if (!is_key_frame) {
-      // Ignore that we have received this complete frame since we are
-      // waiting on a key frame.
-      return;
-    }
-    waiting_for_key_frame_ = false;
-    cast_msg_.missing_frames_and_packets_.clear();
-    cast_msg_.ack_frame_id_ = frame_id;
-    last_update_time_ = clock_->NowTicks();
-    // We might have other complete frames waiting after we receive the last
-    // packet in the key-frame.
-    UpdateAckMessage();
-  } else {
-    if (!UpdateAckMessage())
-      return;
-
-    BuildPacketList();
+
+  if (!UpdateAckMessage(frame_id)) {
+    return;
   }
+  BuildPacketList();
+
   // Send cast message.
   VLOG(2) << "Send cast message Ack:" << static_cast<int>(frame_id);
   cast_feedback_->CastFeedback(cast_msg_);
 }
 
-bool CastMessageBuilder::UpdateAckMessage() {
+bool CastMessageBuilder::UpdateAckMessage(uint32 frame_id) {
   if (!decoder_faster_than_max_frame_rate_) {
     int complete_frame_count = frame_id_map_->NumberOfCompleteFrames();
     if (complete_frame_count > max_unacked_frames_) {
       // We have too many frames pending in our framer; slow down ACK.
-      slowing_down_ack_ = true;
+      if (!slowing_down_ack_) {
+        slowing_down_ack_ = true;
+        ack_queue_.push_back(last_acked_frame_id_);
+      }
     } else if (complete_frame_count <= 1) {
       // We are down to one or less frames in our framer; ACK normally.
       slowing_down_ack_ = false;
+      ack_queue_.clear();
     }
   }
+
   if (slowing_down_ack_) {
     // We are slowing down acknowledgment by acknowledging every other frame.
-    if (acked_last_frame_) {
-      acked_last_frame_ = false;
-    } else {
-      acked_last_frame_ = true;
-      last_acked_frame_id_++;
-      // Note: frame skipping and slowdown ACK is not supported at the same
-      // time; and it's not needed since we can skip frames to catch up.
-    }
-  } else {
-    uint32 frame_id = frame_id_map_->LastContinuousFrame();
-
-    // Is it a new frame?
-    if (last_acked_frame_id_ == frame_id)
+    // Note: frame skipping and slowdown ACK is not supported at the same
+    // time; and it's not needed since we can skip frames to catch up.
+    if (!ack_queue_.empty() && ack_queue_.back() == frame_id) {
       return false;
+    }
+    ack_queue_.push_back(frame_id);
+    if (!acked_last_frame_) {
+      ack_queue_.pop_front();
+    }
+    frame_id = ack_queue_.front();
+  }
 
-    last_acked_frame_id_ = frame_id;
-    acked_last_frame_ = true;
+  acked_last_frame_ = false;
+  // Is it a new frame?
+  if (last_acked_frame_id_ == frame_id) {
+    return false;
   }
+  acked_last_frame_ = true;
+  last_acked_frame_id_ = frame_id;
   cast_msg_.ack_frame_id_ = last_acked_frame_id_;
   cast_msg_.missing_frames_and_packets_.clear();
   last_update_time_ = clock_->NowTicks();
@@ -120,7 +113,6 @@ void CastMessageBuilder::UpdateCastMessage() {
 }
 
 void CastMessageBuilder::Reset() {
-  waiting_for_key_frame_ = true;
   cast_msg_.ack_frame_id_ = kStartFrameId;
   cast_msg_.missing_frames_and_packets_.clear();
   time_last_nacked_map_.clear();
@@ -142,7 +134,8 @@ bool CastMessageBuilder::UpdateCastMessageInternal(RtcpCastMessage* message) {
   }
   last_update_time_ = now;
 
-  UpdateAckMessage();  // Needed to cover when a frame is skipped.
+  // Needed to cover when a frame is skipped.
+  UpdateAckMessage(last_acked_frame_id_);
   BuildPacketList();
   message->Copy(cast_msg_);
   return true;

media/cast/framer/cast_message_builder.h

@@ -7,6 +7,7 @@
 #ifndef MEDIA_CAST_FRAMER_CAST_MESSAGE_BUILDER_H_
 #define MEDIA_CAST_FRAMER_CAST_MESSAGE_BUILDER_H_
 
+#include <deque>
 #include <map>
 
 #include "media/cast/framer/frame_id_map.h"
@@ -30,13 +31,13 @@ class CastMessageBuilder {
                      int max_unacked_frames);
   ~CastMessageBuilder();
 
-  void CompleteFrameReceived(uint32 frame_id, bool is_key_frame);
+  void CompleteFrameReceived(uint32 frame_id);
   bool TimeToSendNextCastMessage(base::TimeTicks* time_to_send);
   void UpdateCastMessage();
   void Reset();
 
  private:
-  bool UpdateAckMessage();
+  bool UpdateAckMessage(uint32 frame_id);
   void BuildPacketList();
   bool UpdateCastMessageInternal(RtcpCastMessage* message);
 
@@ -51,13 +52,13 @@ class CastMessageBuilder {
 
   RtcpCastMessage cast_msg_;
   base::TimeTicks last_update_time_;
-  bool waiting_for_key_frame_;
 
   TimeLastNackMap time_last_nacked_map_;
 
   bool slowing_down_ack_;
   bool acked_last_frame_;
   uint32 last_acked_frame_id_;
+  std::deque<uint32> ack_queue_;
 
   DISALLOW_COPY_AND_ASSIGN(CastMessageBuilder);
 };

media/cast/framer/cast_message_builder_unittest.cc

@@ -112,8 +112,7 @@ class CastMessageBuilderTest : public ::testing::Test {
   void InsertPacket() {
     PacketType packet_type = frame_id_map_.InsertPacket(rtp_header_);
     if (packet_type == kNewPacketCompletingFrame) {
-      cast_msg_builder_->CompleteFrameReceived(rtp_header_.frame_id,
-                                               rtp_header_.is_key_frame);
+      cast_msg_builder_->CompleteFrameReceived(rtp_header_.frame_id);
     }
     cast_msg_builder_->UpdateCastMessage();
   }
@@ -136,26 +135,6 @@ class CastMessageBuilderTest : public ::testing::Test {
   DISALLOW_COPY_AND_ASSIGN(CastMessageBuilderTest);
 };
 
-TEST_F(CastMessageBuilderTest, StartWithAKeyFrame) {
-  SetFrameIds(3, 2);
-  SetPacketId(0);
-  SetMaxPacketId(0);
-  InsertPacket();
-  // Should not trigger ack.
-  EXPECT_FALSE(feedback_.triggered());
-  SetFrameIds(5, 5);
-  SetPacketId(0);
-  SetMaxPacketId(0);
-  SetKeyFrame(true);
-  InsertPacket();
-  frame_id_map_.RemoveOldFrames(5);  // Simulate 5 being pulled for rendering.
-  testing_clock_.Advance(
-      base::TimeDelta::FromMilliseconds(kLongTimeIncrementMs));
-  cast_msg_builder_->UpdateCastMessage();
-  EXPECT_TRUE(feedback_.triggered());
-  EXPECT_EQ(5u, feedback_.last_frame_acked());
-}
-
 TEST_F(CastMessageBuilderTest, OneFrameNackList) {
   SetFrameIds(0, 0);
   SetPacketId(4);
@@ -187,31 +166,6 @@ TEST_F(CastMessageBuilderTest, CompleteFrameMissing) {
   EXPECT_EQ(kRtcpCastAllPacketsLost, feedback_.num_missing_packets(1));
 }
 
-TEST_F(CastMessageBuilderTest, FastForwardAck) {
-  SetFrameIds(1, 0);
-  SetPacketId(0);
-  SetMaxPacketId(0);
-  InsertPacket();
-  EXPECT_FALSE(feedback_.triggered());
-  testing_clock_.Advance(
-      base::TimeDelta::FromMilliseconds(kLongTimeIncrementMs));
-  SetFrameIds(2, 1);
-  SetPacketId(0);
-  SetMaxPacketId(0);
-  InsertPacket();
-  EXPECT_TRUE(feedback_.triggered());
-  EXPECT_EQ(kStartFrameId, feedback_.last_frame_acked());
-  testing_clock_.Advance(
-      base::TimeDelta::FromMilliseconds(kLongTimeIncrementMs));
-  SetFrameIds(0, 0);
-  SetPacketId(0);
-  SetMaxPacketId(0);
-  SetKeyFrame(true);
-  InsertPacket();
-  EXPECT_TRUE(feedback_.triggered());
-  EXPECT_EQ(2u, feedback_.last_frame_acked());
-}
-
 TEST_F(CastMessageBuilderTest, RemoveOldFrames) {
   SetFrameIds(1, 0);
   SetPacketId(0);
@@ -232,7 +186,7 @@ TEST_F(CastMessageBuilderTest, RemoveOldFrames) {
   SetMaxPacketId(5);
   InsertPacket();
   EXPECT_TRUE(feedback_.triggered());
-  EXPECT_EQ(kStartFrameId, feedback_.last_frame_acked());
+  EXPECT_EQ(2u, feedback_.last_frame_acked());
   testing_clock_.Advance(
       base::TimeDelta::FromMilliseconds(kLongTimeIncrementMs));
   SetFrameIds(5, 5);
@@ -260,42 +214,6 @@ TEST_F(CastMessageBuilderTest, RemoveOldFrames) {
   EXPECT_EQ(5u, feedback_.last_frame_acked());
 }
 
-TEST_F(CastMessageBuilderTest, WrapFastForward) {
-  SetFrameIds(254, 254);
-  SetPacketId(0);
-  SetMaxPacketId(1);
-  SetKeyFrame(true);
-  InsertPacket();
-  EXPECT_FALSE(feedback_.triggered());
-  testing_clock_.Advance(
-      base::TimeDelta::FromMilliseconds(kLongTimeIncrementMs));
-  SetFrameIds(255, 254);
-  SetPacketId(0);
-  SetMaxPacketId(0);
-  SetKeyFrame(false);
-  InsertPacket();
-  EXPECT_TRUE(feedback_.triggered());
-  EXPECT_EQ(253u, feedback_.last_frame_acked());
-  testing_clock_.Advance(
-      base::TimeDelta::FromMilliseconds(kLongTimeIncrementMs));
-  SetFrameIds(256, 255);
-  SetPacketId(0);
-  SetMaxPacketId(0);
-  SetKeyFrame(false);
-  InsertPacket();
-  EXPECT_TRUE(feedback_.triggered());
-  EXPECT_EQ(253u, feedback_.last_frame_acked());
-  testing_clock_.Advance(
-      base::TimeDelta::FromMilliseconds(kLongTimeIncrementMs));
-  SetFrameIds(254, 254);
-  SetPacketId(1);
-  SetMaxPacketId(1);
-  SetKeyFrame(true);
-  InsertPacket();
-  EXPECT_TRUE(feedback_.triggered());
-  EXPECT_EQ(256u, feedback_.last_frame_acked());
-}
-
 TEST_F(CastMessageBuilderTest, NackUntilMaxReceivedPacket) {
   SetFrameIds(0, 0);
   SetPacketId(0);
@@ -404,7 +322,7 @@ TEST_F(CastMessageBuilderTest, BasicRps) {
   SetKeyFrame(false);
   InsertPacket();
   EXPECT_TRUE(feedback_.triggered());
-  EXPECT_EQ(0u, feedback_.last_frame_acked());
+  EXPECT_EQ(3u, feedback_.last_frame_acked());
   testing_clock_.Advance(
       base::TimeDelta::FromMilliseconds(kLongTimeIncrementMs));
   frame_id_map_.RemoveOldFrames(3);  // Simulate 3 being pulled for rendering.
@@ -480,16 +398,19 @@ TEST_F(CastMessageBuilderTest, SlowDownAck) {
   // We should now have entered the slowdown ACK state.
   uint32 expected_frame_id = 1;
   for (; frame_id < 10; ++frame_id) {
-    if (frame_id % 2)
+    if (frame_id % 2) {
       ++expected_frame_id;
-    EXPECT_TRUE(feedback_.triggered());
+      EXPECT_TRUE(feedback_.triggered());
+    } else {
+      EXPECT_FALSE(feedback_.triggered());
+    }
     EXPECT_EQ(expected_frame_id, feedback_.last_frame_acked());
     SetFrameIds(frame_id, frame_id - 1);
     InsertPacket();
     testing_clock_.Advance(
         base::TimeDelta::FromMilliseconds(kShortTimeIncrementMs));
   }
-  EXPECT_TRUE(feedback_.triggered());
+  EXPECT_FALSE(feedback_.triggered());
   EXPECT_EQ(expected_frame_id, feedback_.last_frame_acked());
 
   // Simulate frame_id being pulled for rendering.

media/cast/framer/frame_id_map.cc

@@ -137,6 +137,22 @@ bool FrameIdMap::NextContinuousFrame(uint32* frame_id) const {
   return false;
 }
 
+bool FrameIdMap::HaveMultipleDecodableFrames() const {
+  // Find the oldest decodable frame.
+  FrameMap::const_iterator it;
+  bool found_one = false;
+  for (it = frame_map_.begin(); it != frame_map_.end(); ++it) {
+    if (it->second->Complete() && DecodableFrame(it->second.get())) {
+      if (found_one) {
+        return true;
+      } else {
+        found_one = true;
+      }
+    }
+  }
+  return false;
+}
+
 uint32 FrameIdMap::LastContinuousFrame() const {
   uint32 last_continuous_frame_id = last_released_frame_;
   uint32 next_expected_frame = last_released_frame_;
@@ -157,43 +173,16 @@ uint32 FrameIdMap::LastContinuousFrame() const {
   return last_continuous_frame_id;
 }
 
-bool FrameIdMap::NextAudioFrameAllowingMissingFrames(uint32* frame_id) const {
-  // First check if we have continuous frames.
-  if (NextContinuousFrame(frame_id))
-    return true;
-
-  // Find the oldest frame.
-  FrameMap::const_iterator it_best_match = frame_map_.end();
-  FrameMap::const_iterator it;
-
-  // Find first complete frame.
-  for (it = frame_map_.begin(); it != frame_map_.end(); ++it) {
-    if (it->second->Complete()) {
-      it_best_match = it;
-      break;
-    }
-  }
-  if (it_best_match == frame_map_.end())
-    return false;  // No complete frame.
-
-  ++it;
-  for (; it != frame_map_.end(); ++it) {
-    if (it->second->Complete() &&
-        IsOlderFrameId(it->first, it_best_match->first)) {
-      it_best_match = it;
-    }
-  }
-  *frame_id = it_best_match->first;
-  return true;
-}
-
-bool FrameIdMap::NextVideoFrameAllowingSkippingFrames(uint32* frame_id) const {
+bool FrameIdMap::NextFrameAllowingSkippingFrames(uint32* frame_id) const {
   // Find the oldest decodable frame.
   FrameMap::const_iterator it_best_match = frame_map_.end();
   FrameMap::const_iterator it;
   for (it = frame_map_.begin(); it != frame_map_.end(); ++it) {
-    if (it->second->Complete() && DecodableVideoFrame(it->second.get())) {
-      it_best_match = it;
+    if (it->second->Complete() && DecodableFrame(it->second.get())) {
+      if (it_best_match == frame_map_.end() ||
+          IsOlderFrameId(it->first, it_best_match->first)) {
+        it_best_match = it;
+      }
     }
   }
   if (it_best_match == frame_map_.end())
@@ -237,11 +226,14 @@ bool FrameIdMap::ContinuousFrame(FrameInfo* frame) const {
   return static_cast<uint32>(last_released_frame_ + 1) == frame->frame_id();
 }
 
-bool FrameIdMap::DecodableVideoFrame(FrameInfo* frame) const {
+bool FrameIdMap::DecodableFrame(FrameInfo* frame) const {
   if (frame->is_key_frame())
     return true;
   if (waiting_for_key_ && !frame->is_key_frame())
     return false;
+  // Self-reference?
+  if (frame->referenced_frame_id() == frame->frame_id())
+    return true;
 
   // Current frame is not necessarily referencing the last frame.
   // Do we have the reference frame?

media/cast/framer/frame_id_map.h

@@ -64,8 +64,8 @@ class FrameIdMap {
   bool NextContinuousFrame(uint32* frame_id) const;
   uint32 LastContinuousFrame() const;
 
-  bool NextAudioFrameAllowingMissingFrames(uint32* frame_id) const;
-  bool NextVideoFrameAllowingSkippingFrames(uint32* frame_id) const;
+  bool NextFrameAllowingSkippingFrames(uint32* frame_id) const;
+  bool HaveMultipleDecodableFrames() const;
 
   int NumberOfCompleteFrames() const;
   void GetMissingPackets(uint32 frame_id,
@@ -74,7 +74,7 @@ class FrameIdMap {
 
  private:
   bool ContinuousFrame(FrameInfo* frame) const;
-  bool DecodableVideoFrame(FrameInfo* frame) const;
+  bool DecodableFrame(FrameInfo* frame) const;
 
   FrameMap frame_map_;
   bool waiting_for_key_;

media/cast/framer/framer.cc

@@ -58,42 +58,15 @@ bool Framer::InsertPacket(const uint8* payload_data,
     it->second->InsertPacket(payload_data, payload_size, rtp_header);
   }
 
-  bool complete = (packet_type == kNewPacketCompletingFrame);
-  if (complete) {
-    // ACK as soon as possible.
-    VLOG(2) << "Complete frame " << static_cast<int>(rtp_header.frame_id);
-    cast_msg_builder_->CompleteFrameReceived(rtp_header.frame_id,
-                                             rtp_header.is_key_frame);
-  }
-  return complete;
+  return packet_type == kNewPacketCompletingFrame;
 }
 
 // This does not release the frame.
-bool Framer::GetEncodedAudioFrame(transport::EncodedFrame* audio_frame,
-                                  bool* next_frame) {
-  uint32 frame_id;
-  // Find frame id.
-  if (frame_id_map_.NextContinuousFrame(&frame_id)) {
-    // We have our next frame.
-    *next_frame = true;
-  } else {
-    if (!frame_id_map_.NextAudioFrameAllowingMissingFrames(&frame_id)) {
-      return false;
-    }
-    *next_frame = false;
-  }
+bool Framer::GetEncodedFrame(transport::EncodedFrame* frame,
+                             bool* next_frame,
+                             bool* have_multiple_decodable_frames) {
+  *have_multiple_decodable_frames = frame_id_map_.HaveMultipleDecodableFrames();
 
-  ConstFrameIterator it = frames_.find(frame_id);
-  DCHECK(it != frames_.end());
-  if (it == frames_.end())
-    return false;
-
-  return it->second->AssembleEncodedFrame(audio_frame);
-}
-
-// This does not release the frame.
-bool Framer::GetEncodedVideoFrame(transport::EncodedFrame* video_frame,
-                                  bool* next_frame) {
   uint32 frame_id;
   // Find frame id.
   if (frame_id_map_.NextContinuousFrame(&frame_id)) {
@@ -104,18 +77,23 @@ bool Framer::GetEncodedVideoFrame(transport::EncodedFrame* video_frame,
     if (!decoder_faster_than_max_frame_rate_)
       return false;
 
-    if (!frame_id_map_.NextVideoFrameAllowingSkippingFrames(&frame_id)) {
+    if (!frame_id_map_.NextFrameAllowingSkippingFrames(&frame_id)) {
       return false;
     }
     *next_frame = false;
   }
 
+  if (*next_frame) {
+    VLOG(2) << "ACK frame " << frame_id;
+    cast_msg_builder_->CompleteFrameReceived(frame_id);
+  }
+
   ConstFrameIterator it = frames_.find(frame_id);
   DCHECK(it != frames_.end());
   if (it == frames_.end())
     return false;
 
-  return it->second->AssembleEncodedFrame(video_frame);
+  return it->second->AssembleEncodedFrame(frame);
 }
 
 void Framer::Reset() {

media/cast/framer/framer.h

@@ -40,15 +40,14 @@ class Framer {
                     const RtpCastHeader& rtp_header,
                     bool* duplicate);
 
-  // Extracts a complete encoded frame - will only return a complete continuous
-  // frame.
-  // Returns false if the frame does not exist or if the frame is not complete
-  // within the given time frame.
-  bool GetEncodedVideoFrame(transport::EncodedFrame* video_frame,
-                            bool* next_frame);
-
-  bool GetEncodedAudioFrame(transport::EncodedFrame* audio_frame,
-                            bool* next_frame);
+  // Extracts a complete encoded frame - will only return a complete and
+  // decodable frame. Returns false if no such frames exist.
+  // |next_frame| will be set to true if the returned frame is the very
+  // next frame. |have_multiple_complete_frames| will be set to true
+  // if there are more decodadble frames available.
+  bool GetEncodedFrame(transport::EncodedFrame* video_frame,
+                       bool* next_frame,
+                       bool* have_multiple_complete_frames);
 
   void ReleaseFrame(uint32 frame_id);
 

media/cast/video_receiver/video_receiver.cc

@@ -155,19 +155,30 @@ void VideoReceiver::EmitAvailableEncodedFrames() {
     scoped_ptr<transport::EncodedFrame> encoded_frame(
         new transport::EncodedFrame());
     bool is_consecutively_next_frame = false;
-    if (!framer_.GetEncodedVideoFrame(encoded_frame.get(),
-                                      &is_consecutively_next_frame)) {
+    bool have_multiple_complete_frames = false;
+
+    if (!framer_.GetEncodedFrame(encoded_frame.get(),
+                                 &is_consecutively_next_frame,
+                                 &have_multiple_complete_frames)) {
       VLOG(1) << "Wait for more video packets to produce a completed frame.";
       return;  // OnReceivedPayloadData() will invoke this method in the future.
     }
 
+    const base::TimeTicks now = cast_environment_->Clock()->NowTicks();
+    const base::TimeTicks playout_time =
+        GetPlayoutTime(now, encoded_frame->rtp_timestamp);
+
+    // If we have multiple decodable frames, and the current frame is
+    // too old, then skip it and decode the next frame instead.
+    if (have_multiple_complete_frames && now > playout_time) {
+      framer_.ReleaseFrame(encoded_frame->frame_id);
+      continue;
+    }
+
     // If |framer_| has a frame ready that is out of sequence, examine the
     // playout time to determine whether it's acceptable to continue, thereby
     // skipping one or more frames.  Skip if the missing frame wouldn't complete
     // playing before the start of playback of the available frame.
-    const base::TimeTicks now = cast_environment_->Clock()->NowTicks();
-    const base::TimeTicks playout_time =
-        GetPlayoutTime(now, encoded_frame->rtp_timestamp);
     if (!is_consecutively_next_frame) {
       // TODO(miu): Also account for expected decode time here?
       const base::TimeTicks earliest_possible_end_time_of_missing_frame =