Implementing preload=metadata for video

media/base/filters.h

 // Copyright (c) 2011 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.
 
 // Filters are connected in a strongly typed manner, with downstream filters
 // always reading data from upstream filters.  Upstream filters have no clue
 // who is actually reading from them, and return the results via callbacks.
 //
 //                         DemuxerStream(Video) <- VideoDecoder <- VideoRenderer
 // DataSource <- Demuxer <
@@ skipping 25 matching lines @@
 namespace media {
 
 class Buffer;
 class Decoder;
 class DemuxerStream;
 class Filter;
 class FilterHost;
 
 struct PipelineStatistics;
 
+// Used to specify video preload states. They are "hints" to the browser about
+// how aggressively the browser should load and buffer data.
+// Please see the HTML5 spec for the descriptions of these values:
+// http://www.w3.org/TR/html5/video.html#attr-media-preload
+//
+// Enum values must match the values in WebCore::MediaPlayer::Preload.
+enum Preload {
+  PRELOAD_NONE,

[acolwell GONE FROM CHROMIUM, 2011/03/29 05:52:03]

nit: How about dropping the PRELOAD_ prefix now that your comments got me
thinking about this. We should probably keep it MACRO_STYLE here since the other
enums in here are in that style.

[vrk (LEFT CHROMIUM), 2011/03/30 17:41:44]

Done.

+  PRELOAD_METADATA,
+  PRELOAD_AUTO,
+};
+
 // Used for completing asynchronous methods.
 typedef Callback0::Type FilterCallback;
 
 // Used for updating pipeline statistics.
 typedef Callback1<const PipelineStatistics&>::Type StatisticsCallback;
 
 class Filter : public base::RefCountedThreadSafe<Filter> {
  public:
   Filter();
 
@@ skipping 64 matching lines @@
   virtual void Read(int64 position, size_t size,
                     uint8* data, ReadCallback* read_callback) = 0;
 
   // Returns true and the file size, false if the file size could not be
   // retrieved.
   virtual bool GetSize(int64* size_out) = 0;
 
   // Returns true if we are performing streaming. In this case seeking is
   // not possible.
   virtual bool IsStreaming() = 0;
+
+  // Alert the DataSource that the video preload value has been changed.
+  virtual void SetPreload(Preload preload) = 0;
 };
 
 class DemuxerStream : public base::RefCountedThreadSafe<DemuxerStream> {
  public:
   enum Type {
     UNKNOWN,
     AUDIO,
     VIDEO,
     NUM_TYPES,  // Always keep this entry as the last one!
   };
@@ skipping 33 matching lines @@
   virtual void* QueryInterface(const char* interface_id);
 
   friend class base::RefCountedThreadSafe<DemuxerStream>;
   virtual ~DemuxerStream();
 };
 
 class Demuxer : public Filter {
  public:
   // Returns the given stream type, or NULL if that type is not present.
   virtual scoped_refptr<DemuxerStream> GetStream(DemuxerStream::Type type) = 0;
+
+  // Alert the Demuxer that the video preload value has been changed.
+  virtual void SetPreload(Preload preload) = 0;
 };
 
 
 class VideoDecoder : public Filter {
  public:
   // Initialize a VideoDecoder with the given DemuxerStream, executing the
   // callback upon completion.
   // stats_callback is used to update global pipeline statistics.
   virtual void Initialize(DemuxerStream* stream, FilterCallback* callback,
                           StatisticsCallback* stats_callback) = 0;
@@ skipping 92 matching lines @@
   // buffer.
   virtual bool HasEnded() = 0;
 
   // Sets the output volume.
   virtual void SetVolume(float volume) = 0;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_FILTERS_H_