Introduce audio/video BufferingState to Pipeline.

This is a stepping stone towards having audio/video renderers accurately
report their buffering state. For now we use the Preroll() callback to
signal that enough data has been buffered.

Notable changes:
  - The kStarting/kStarted states have been merged into kPlaying
  - DoPlay() is now done implicitly after entering the kPlaying state
  - Transitioning from waiting to non-waiting states (or vice versa)
    now controls the starting and stopping of playback

BUG=144683

Review URL: https://codereview.chromium.org/276973004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@269828 0039d316-1c4b-4281-b951-d872f2087c98

media/base/buffering_state.h

+// 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.
+
+#ifndef MEDIA_BASE_BUFFERING_STATE_H_
+#define MEDIA_BASE_BUFFERING_STATE_H_
+
+#include "base/callback_forward.h"
+
+namespace media {
+
+enum BufferingState {
+  // Indicates that there is no data buffered.
+  //
+  // Typical reason is data underflow and hence playback should be paused.
+  BUFFERING_HAVE_NOTHING,
+
+  // Indicates that enough data has been buffered.
+  //
+  // Typical reason is enough data has been prerolled to start playback.
+  BUFFERING_HAVE_ENOUGH,
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_BUFFERING_STATE_H_

media/base/pipeline.h

@@ -13,6 +13,7 @@
 #include "base/threading/thread_checker.h"
 #include "base/time/default_tick_clock.h"
 #include "media/base/audio_renderer.h"
+#include "media/base/buffering_state.h"
 #include "media/base/demuxer.h"
 #include "media/base/media_export.h"
 #include "media/base/pipeline_status.h"
@@ -58,14 +59,13 @@ typedef base::Callback<void(PipelineMetadata)> PipelineMetadataCB;
 //   [ InitXXX (for each filter) ]      [ Stopping ]
 //         |                                 |
 //         V                                 V
-//   [ InitPreroll ]                    [ Stopped ]
+//   [ InitPrerolling ]                 [ Stopped ]
 //         |
 //         V
-//   [ Starting ] <-- [ Seeking ]
+//   [ Playing ] <-- [ Seeking ]
 //         |               ^
-//         V               |
-//   [ Started ] ----------'
-//                 Seek()
+//         `---------------'
+//              Seek()
 //
 // Initialization is a series of state transitions from "Created" through each
 // filter initialization state.  When all filter initialization states have
@@ -194,8 +194,7 @@ class MEDIA_EXPORT Pipeline : public DemuxerHost {
     kInitVideoRenderer,
     kInitPrerolling,
     kSeeking,
-    kStarting,
-    kStarted,
+    kPlaying,
     kStopping,
     kStopped,
   };
@@ -305,10 +304,6 @@ class MEDIA_EXPORT Pipeline : public DemuxerHost {
   // indepentent from seeking.
   void DoSeek(base::TimeDelta seek_timestamp, const PipelineStatusCB& done_cb);
 
-  // Updates playback rate and volume and initiates an asynchronous play call
-  // sequence executing |done_cb| with the final status when completed.
-  void DoPlay(const PipelineStatusCB& done_cb);
-
   // Initiates an asynchronous pause-flush-stop call sequence executing
   // |done_cb| when completed.
   void DoStop(const PipelineStatusCB& done_cb);
@@ -316,6 +311,21 @@ class MEDIA_EXPORT Pipeline : public DemuxerHost {
 
   void OnAudioUnderflow();
 
+  // Collection of callback methods and helpers for tracking changes in
+  // buffering state and transition from paused/underflow states and playing
+  // states.
+  //
+  // While in the kPlaying state:
+  //   - A waiting to non-waiting transition indicates preroll has completed
+  //     and StartPlayback() should be called
+  //   - A non-waiting to waiting transition indicates underflow has occurred
+  //     and StartWaitingForEnoughData() should be called
+  void BufferingStateChanged(BufferingState* buffering_state,
+                             BufferingState new_buffering_state);
+  bool WaitingForEnoughData() const;
+  void StartWaitingForEnoughData();
+  void StartPlayback();
+
   void StartClockIfWaitingForTimeUpdate_Locked();
 
   // Task runner used to execute pipeline tasks.
@@ -377,6 +387,9 @@ class MEDIA_EXPORT Pipeline : public DemuxerHost {
   bool video_ended_;
   bool text_ended_;
 
+  BufferingState audio_buffering_state_;
+  BufferingState video_buffering_state_;
+
   // Temporary callback used for Start() and Seek().
   PipelineStatusCB seek_cb_;
 

media/base/pipeline_unittest.cc

@@ -860,7 +860,6 @@ class PipelineTeardownTest : public PipelineTest {
     kFlushing,
     kSeeking,
     kPrerolling,
-    kStarting,
     kPlaying,
   };
 
@@ -885,7 +884,6 @@ class PipelineTeardownTest : public PipelineTest {
       case kFlushing:
       case kSeeking:
       case kPrerolling:
-      case kStarting:
         DoInitialize(state, stop_or_error);
         DoSeek(state, stop_or_error);
         break;
@@ -1107,18 +1105,6 @@ class PipelineTeardownTest : public PipelineTest {
     EXPECT_CALL(*video_renderer_, SetPlaybackRate(0.0f));
     EXPECT_CALL(*audio_renderer_, SetVolume(1.0f));
 
-    if (state == kStarting) {
-      if (stop_or_error == kStop) {
-        EXPECT_CALL(*audio_renderer_, Play())
-            .WillOnce(Stop(pipeline_.get(), stop_cb));
-      } else {
-        status = PIPELINE_ERROR_READ;
-        EXPECT_CALL(*audio_renderer_, Play())
-            .WillOnce(SetError(pipeline_.get(), status));
-      }
-      return status;
-    }
-
     NOTREACHED() << "State not supported: " << state;
     return status;
   }
@@ -1168,7 +1154,6 @@ INSTANTIATE_TEARDOWN_TEST(Stop, Pausing);
 INSTANTIATE_TEARDOWN_TEST(Stop, Flushing);
 INSTANTIATE_TEARDOWN_TEST(Stop, Seeking);
 INSTANTIATE_TEARDOWN_TEST(Stop, Prerolling);
-INSTANTIATE_TEARDOWN_TEST(Stop, Starting);
 INSTANTIATE_TEARDOWN_TEST(Stop, Playing);
 
 INSTANTIATE_TEARDOWN_TEST(Error, InitDemuxer);
@@ -1178,7 +1163,6 @@ INSTANTIATE_TEARDOWN_TEST(Error, Pausing);
 INSTANTIATE_TEARDOWN_TEST(Error, Flushing);
 INSTANTIATE_TEARDOWN_TEST(Error, Seeking);
 INSTANTIATE_TEARDOWN_TEST(Error, Prerolling);
-INSTANTIATE_TEARDOWN_TEST(Error, Starting);
 INSTANTIATE_TEARDOWN_TEST(Error, Playing);
 
 INSTANTIATE_TEARDOWN_TEST(ErrorAndStop, Playing);

media/media.gyp

@@ -248,6 +248,7 @@
         'base/bit_reader_core.cc',
         'base/bit_reader_core.h',
         'base/bitstream_buffer.h',
+        'base/buffering_state.h',
         'base/buffers.h',
         'base/byte_queue.cc',
         'base/byte_queue.h',