Cast: Don't cancel re-transmission for some cases

media/cast/video_sender/video_sender.cc

 // Copyright 2013 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/cast/video_sender/video_sender.h"
 
 #include <algorithm>
 #include <cstring>
 
 #include "base/bind.h"
@@ skipping 298 matching lines @@
     }
     // TODO(miu): The values "2" and "3" should be derived from configuration.
     if (duplicate_ack_counter_ >= 2 && duplicate_ack_counter_ % 3 == 2) {
       VLOG(1) << "Received duplicate ACK for frame " << latest_acked_frame_id_;
       ResendForKickstart();
     }
   } else {
     // Only count duplicated ACKs if there is no NACK request in between.
     // This is to avoid aggresive resend.
     duplicate_ack_counter_ = 0;
+
+    // A NACK is also used to cancel pending re-transmissions.
     transport_sender_->ResendPackets(
-        false, cast_feedback.missing_frames_and_packets_);
+        false, cast_feedback.missing_frames_and_packets_, true);
     uint32 new_bitrate = 0;
     if (congestion_control_.OnNack(rtt, &new_bitrate)) {
       UpdateBitrate(new_bitrate);
     }
   }
 
   RtpTimestamp rtp_timestamp =
       frame_id_to_rtp_timestamp_[cast_feedback.ack_frame_id_ & 0xff];
   cast_environment_->Logging()->InsertFrameEvent(
       cast_environment_->Clock()->NowTicks(), FRAME_ACK_RECEIVED, VIDEO_EVENT,
@@ skipping 29 matching lines @@
           << " to kick-start.";
   // Send the first packet of the last encoded frame to kick start
   // retransmission. This gives enough information to the receiver what
   // packets and frames are missing.
   MissingFramesAndPacketsMap missing_frames_and_packets;
   PacketIdSet missing;
   missing.insert(0);
   missing_frames_and_packets.insert(
       std::make_pair(last_sent_frame_id_, missing));
   last_send_time_ = cast_environment_->Clock()->NowTicks();
-  transport_sender_->ResendPackets(false, missing_frames_and_packets);
+
+  // Sending this extra packet is to kick-start the session. There is
+  // no need to optimize re-transmission for this case.
+  transport_sender_->ResendPackets(false, missing_frames_and_packets,
+                                   false);
 }
 
 void VideoSender::UpdateBitrate(int new_bitrate) {
   // Make sure we don't set the bitrate too insanely low.
   DCHECK_GT(new_bitrate, 1000);
   video_encoder_->SetBitRate(new_bitrate);
   current_requested_bitrate_ = new_bitrate;
 }
 
 }  // namespace cast
 }  // namespace media