Allow transitioning to HAVE_METADATA before pipeline initialization completes.

media/base/pipeline.h

 // Copyright (c) 2012 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_PIPELINE_H_
 #define MEDIA_BASE_PIPELINE_H_
 
 #include <string>
 
 #include "base/gtest_prod_util.h"
@@ skipping 79 matching lines @@
 // From then on the normal Seek() transitions are carried out and we start
 // playing the media.
 //
 // If any error ever happens, this object will transition to the "Error" state
 // from any state. If Stop() is ever called, this object will transition to
 // "Stopped" state.
 class MEDIA_EXPORT Pipeline
     : public base::RefCountedThreadSafe<Pipeline>,
       public DemuxerHost {
  public:
+  // Current buffering state in terms of HTMLMediaElement.readyState values.

[scherkus (not reviewing), 2012/08/15 23:46:55]

layering violation in comment form!

instead of a catch-all comment we should define these states in terms of
pipeline operations (i.e., kHaveMetadata -> natural size / duration / etc... are
queryable)

[acolwell GONE FROM CHROMIUM, 2012/08/16 00:54:18]

Done.

+  enum ReadyState {
+    kHaveMetadata,
+    kHaveEnoughData,
+  };
+
+  typedef base::Callback<void(ReadyState)> ReadyStateCB;
+
   // Constructs a media pipeline that will execute on |message_loop|.
   Pipeline(const scoped_refptr<base::MessageLoopProxy>& message_loop,
            MediaLog* media_log);
 
   // Build a pipeline to using the given filter collection to construct a filter
-  // chain, executing |start_cb| when initialization has completed.
+  // chain, executing |seek_cb| when the initial seek/preroll has completed.
   //
   // The following permanent callbacks will be executed as follows up until
   // Stop() has completed:
   //   |ended_cb| will be executed whenever the media reaches the end.
   //   |error_cb| will be executed whenever an error occurs but hasn't
   //              been reported already through another callback.
-  //
+  //   |ready_state_cb| will be executed whenever the pipeline does something
+  //                    that should trigger a HTMLMediaElement.readyState

[scherkus (not reviewing), 2012/08/15 23:46:55]

ditto -- this comment shouldn't reference what the client should do (it's up to
the client!)

what about mentioning that this cb is optional?

[acolwell GONE FROM CHROMIUM, 2012/08/16 00:54:18]

Done.

+  //                    transition.
   // It is an error to call this method after the pipeline has already started.
   void Start(scoped_ptr<FilterCollection> filter_collection,
              const PipelineStatusCB& ended_cb,
              const PipelineStatusCB& error_cb,
-             const PipelineStatusCB& start_cb);
+             const PipelineStatusCB& seek_cb,
+             const ReadyStateCB& ready_state_cb);
 
   // Asynchronously stops the pipeline, executing |stop_cb| when the pipeline
   // teardown has completed.
   //
   // Stop() must complete before destroying the pipeline. It it permissible to
   // call Stop() at any point during the lifetime of the pipeline.
   void Stop(const base::Closure& stop_cb);
 
   // Attempt to seek to the position specified by time.  |seek_cb| will be
   // executed when the all filters in the pipeline have processed the seek.
@@ skipping 98 matching lines @@
 
   // Updates |state_|. All state transitions should use this call.
   void SetState(State next_state);
 
   // Simple method used to make sure the pipeline is running normally.
   bool IsPipelineOk();
 
   // Helper method to tell whether we are in transition to seek state.
   bool IsPipelineSeeking();
 
-  // Helper method to execute callback from Start() and reset
-  // |filter_collection_|. Called when initialization completes
-  // normally or when pipeline is stopped or error occurs during
-  // initialization.
-  void FinishInitialization();
+  // Helper method that runs & resets |seek_cb_| and resets |seek_timestamp_|
+  // and |seek_pending_|.
+  void FinishSeek();
 
   // Returns true if the given state is one that transitions to a new state
   // after iterating through each filter.
   static bool TransientState(State state);
 
   // Given the current state, returns the next state.
   State FindNextState(State current);
 
   // DataSourceHost (by way of DemuxerHost) implementation.
   virtual void SetTotalBytes(int64 total_bytes) OVERRIDE;
@@ skipping 38 matching lines @@
 
   // Callback executed by video renderer to update clock time.
   void OnVideoTimeUpdate(base::TimeDelta max_time);
 
   // The following "task" methods correspond to the public methods, but these
   // methods are run as the result of posting a task to the PipelineInternal's
   // message loop.
   void StartTask(scoped_ptr<FilterCollection> filter_collection,
                  const PipelineStatusCB& ended_cb,
                  const PipelineStatusCB& error_cb,
-                 const PipelineStatusCB& start_cb);
+                 const PipelineStatusCB& seek_cb,
+                 const ReadyStateCB& ready_state_cb);
 
   // InitializeTask() performs initialization in multiple passes. It is executed
   // as a result of calling Start() or InitializationComplete() that advances
   // initialization to the next state. It works as a hub of state transition for
   // initialization.  One stage communicates its status to the next through
   // |last_stage_status|.
   void InitializeTask(PipelineStatus last_stage_status);
 
   // Stops and destroys all filters, placing the pipeline in the kStopped state.
   void StopTask(const base::Closure& stop_cb);
@@ skipping 177 matching lines @@
   bool audio_disabled_;
 
   // Filter collection as passed in by Start().
   scoped_ptr<FilterCollection> filter_collection_;
 
   // Callbacks for various pipeline operations.
   PipelineStatusCB seek_cb_;
   base::Closure stop_cb_;
   PipelineStatusCB ended_cb_;
   PipelineStatusCB error_cb_;
+  ReadyStateCB ready_state_cb_;
 
   // Audio renderer reference used for setting the volume and determining
   // when playback has finished.
   scoped_refptr<AudioRenderer> audio_renderer_;
 
   // Video Renderer reference used for determining when playback has finished
   // and for signalling imminent shutdown.
   // The signalling imminent shutdown is a HACK necessary because
   // WebMediaPlayerImpl::Destroy() holds the render thread loop hostage
   // until PipelineImpl::Stop() calls its callback.
@@ skipping 15 matching lines @@
   base::Time creation_time_;
 
   scoped_ptr<SerialRunner> pending_callbacks_;
 
   DISALLOW_COPY_AND_ASSIGN(Pipeline);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_PIPELINE_H_