media: Introduce DemuxerStreamProvider interface.

media/base/demuxer_stream_provider.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_DEMUXER_STREAM_PROVIDER_H_
+#define MEDIA_BASE_DEMUXER_STREAM_PROVIDER_H_
+
+#include "media/base/demuxer_stream.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+class MEDIA_EXPORT DemuxerStreamProvider {
+ public:
+  enum Liveness {
+    LIVENESS_UNKNOWN,
+    LIVENESS_RECORDED,
+    LIVENESS_LIVE,
+  };
+
+  DemuxerStreamProvider();
+  virtual ~DemuxerStreamProvider();
+
+  // Returns the first stream of the given stream type (which is not allowed

[tim (not reviewing), 2014/09/03 22:43:02]

OOC as someone using DemuxerStreamProvider, when do I have to worry about
multiple streams?  Is the notion of "streams other than the first stream"
something this layer can even deal with?

[xhwang, 2014/09/03 23:45:25]

This is moved from the old Demuxer code. Basically we don't support multiple
audio or multiple video streams. But we do support one audio stream and one
video stream.

Currently you only need to worry about a DemuxerStreamProvider that provides
only one audio stream.

In the future, we need to think about how to support audio + video. I imagine
we'll have a DataPipe for each stream we support.

+  // to be DemuxerStream::TEXT), or NULL if that type of stream is not present.
+  virtual DemuxerStream* GetStream(DemuxerStream::Type type) = 0;
+
+  // Returns liveness of the streams provided, i.e. whether recorded or live.
+  virtual Liveness GetLiveness() const = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DemuxerStreamProvider);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_DEMUXER_STREAM_PROVIDER_H_