media/base/text_renderer.h

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef MEDIA_BASE_TEXT_RENDERER_H_
   6 #define MEDIA_BASE_TEXT_RENDERER_H_
   7
   8 #include <map>
   9 #include <set>
  10
  11 #include "base/callback.h"
  12 #include "base/memory/scoped_ptr.h"
  13 #include "base/memory/weak_ptr.h"
  14 #include "media/base/demuxer_stream.h"
  15 #include "media/base/media_export.h"
  16 #include "media/base/pipeline_status.h"
  17 #include "media/base/text_track.h"
  18
  19 namespace base {
  20 class SingleThreadTaskRunner;
  21 }
  22
  23 namespace media {
  24
  25 class TextCue;
  26 class TextTrackConfig;
  27
  28 // Receives decoder buffers from the upstream demuxer, decodes them to text
  29 // cues, and then passes them onto the TextTrack object associated with each
  30 // demuxer text stream.
  31 class MEDIA_EXPORT TextRenderer {
  32  public:
  33   // |task_runner| is the thread on which TextRenderer will execute.
  34   //
  35   // |add_text_track_cb] is called when the demuxer requests (via its host)
  36   // that a new text track be created.
  37   TextRenderer(
  38       const scoped_refptr<base::SingleThreadTaskRunner>& task_runner,
  39       const AddTextTrackCB& add_text_track_cb);
  40   ~TextRenderer();
  41
  42   // |ended_cb| is executed when all of the text tracks have reached
  43   // end of stream, following a play request.
  44   void Initialize(const base::Closure& ended_cb);
  45
  46   // Start text track cue decoding and rendering, executing |callback| when
  47   // playback is underway.
  48   void Play(const base::Closure& callback);
  49
  50   // Temporarily suspend decoding and rendering, executing |callback| when
  51   // playback has been suspended.
  52   void Pause(const base::Closure& callback);
  53
  54   // Discard any text data, executing |callback| when completed.
  55   void Flush(const base::Closure& callback);
  56
  57   // Stop all operations in preparation for being deleted, executing |callback|
  58   // when complete.
  59   void Stop(const base::Closure& callback);
  60
  61   // Add new |text_stream|, having the indicated |config|, to the text stream
  62   // collection managed by this text renderer.
  63   void AddTextStream(DemuxerStream* text_stream,
  64                      const TextTrackConfig& config);
  65
  66   // Remove |text_stream| from the text stream collection.
  67   void RemoveTextStream(DemuxerStream* text_stream);
  68
  69   // Returns true if there are extant text tracks.
  70   bool HasTracks() const;
  71
  72  private:
  73   struct TextTrackState {
  74     // To determine read progress.
  75     enum ReadState {
  76       kReadIdle,
  77       kReadPending
  78     };
  79
  80     explicit TextTrackState(scoped_ptr<TextTrack> text_track);
  81     ~TextTrackState();
  82
  83     ReadState read_state;
  84     scoped_ptr<TextTrack> text_track;
  85   };
  86
  87   // Callback delivered by the demuxer |text_stream| when
  88   // a read from the stream completes.
  89   void BufferReady(DemuxerStream* text_stream,
  90                    DemuxerStream::Status status,
  91                    const scoped_refptr<DecoderBuffer>& input);
  92
  93   // Dispatches the decoded cue delivered on the demuxer's |text_stream|.
  94   void CueReady(DemuxerStream* text_stream,
  95                 const scoped_refptr<TextCue>& text_cue);
  96
  97   // Dispatched when the AddTextTrackCB completes, after having created
  98   // the TextTrack object associated with |text_stream|.
  99   void OnAddTextTrackDone(DemuxerStream* text_stream,
 100                           scoped_ptr<TextTrack> text_track);
 101
 102   // Utility function to post a read request on |text_stream|.
 103   void Read(TextTrackState* state, DemuxerStream* text_stream);
 104
 105   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
 106   base::WeakPtrFactory<TextRenderer> weak_factory_;
 107   base::WeakPtr<TextRenderer> weak_this_;
 108   const AddTextTrackCB add_text_track_cb_;
 109
 110   // Callbacks provided during Initialize().
 111   base::Closure ended_cb_;
 112
 113   // Callback provided to Pause().
 114   base::Closure pause_cb_;
 115
 116   // Callback provided to Stop().
 117   base::Closure stop_cb_;
 118
 119   // Simple state tracking variable.
 120   enum State {
 121     kUninitialized,
 122     kPausePending,
 123     kPaused,
 124     kPlaying,
 125     kEnded,
 126     kStopPending,
 127     kStopped
 128   };
 129   State state_;
 130
 131   typedef std::map<DemuxerStream*, TextTrackState*> TextTrackStateMap;
 132   TextTrackStateMap text_track_state_map_;
 133
 134   // Indicates how many read requests are in flight.
 135   int pending_read_count_;
 136
 137   // Indicates which text streams have not delivered end-of-stream yet.
 138   typedef std::set<DemuxerStream*> PendingEosSet;
 139   PendingEosSet pending_eos_set_;
 140
 141   DISALLOW_IMPLICIT_CONSTRUCTORS(TextRenderer);
 142 };
 143
 144 }  // namespace media
 145
 146 #endif  // MEDIA_BASE_TEXT_RENDERER_H_