Cast: Make vp8 3-buffer mode work

media/cast/receiver/frame_receiver.cc

 // Copyright 2014 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/receiver/frame_receiver.h"
 
 #include <algorithm>
 
 #include "base/big_endian.h"
 #include "base/bind.h"
@@ skipping 198 matching lines @@
     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.
     if (!is_consecutively_next_frame) {
-      // TODO(miu): Also account for expected decode time here?
+      // This assumes that decoding takes as long as playing, which might
+      // not be true.
       const base::TimeTicks earliest_possible_end_time_of_missing_frame =
-          now + expected_frame_duration_;
+          now + expected_frame_duration_ * 2;
       if (earliest_possible_end_time_of_missing_frame < playout_time) {
         VLOG(1) << "Wait for next consecutive frame instead of skipping.";
         if (!is_waiting_for_consecutive_frame_) {
           is_waiting_for_consecutive_frame_ = true;
           cast_environment_->PostDelayedTask(
               CastEnvironment::MAIN,
               FROM_HERE,
               base::Bind(&FrameReceiver::EmitAvailableEncodedFramesAfterWaiting,
                          weak_factory_.GetWeakPtr()),
               playout_time - now);
         }
         return;
       }
     }
 
+    // At this point, we have the complete next frame, or a decodable
+    // frame from somewhere later in the stream, AND we have given up
+    // on waiting for any frames in between, so now we can ACK the frame.
+    framer_.AckFrame(encoded_frame->frame_id);
+
     // Decrypt the payload data in the frame, if crypto is being used.
     if (decryptor_.is_activated()) {
       std::string decrypted_data;
       if (!decryptor_.Decrypt(encoded_frame->frame_id,
                               encoded_frame->data,
                               &decrypted_data)) {
         // Decryption failed.  Give up on this frame.
         framer_.ReleaseFrame(encoded_frame->frame_id);
         continue;
       }
@@ skipping 73 matching lines @@
 }
 
 void FrameReceiver::SendNextRtcpReport() {
   DCHECK(cast_environment_->CurrentlyOn(CastEnvironment::MAIN));
   rtcp_.SendRtcpFromRtpReceiver(NULL, base::TimeDelta(), NULL, &stats_);
   ScheduleNextRtcpReport();
 }
 
 }  // namespace cast
 }  // namespace media