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diff --git a/media/formats/mp4/bitstream_converter.h b/media/formats/mp4/bitstream_converter.h
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+++ b/media/formats/mp4/bitstream_converter.h
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+// Copyright 2015 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_FORMATS_MP4_BITSTREAM_CONVERTER_H_
+#define MEDIA_FORMATS_MP4_BITSTREAM_CONVERTER_H_
+
+#include <vector>
+
+#include "base/basictypes.h"
+#include "base/memory/ref_counted.h"
+
+namespace media {
+
+struct SubsampleEntry;
+
+namespace mp4 {
+
+// BitstreamConverter provides a unified interface for performing some common
+// bitstream conversions (e.g. H.264 MP4 bitstream to Annex B, and elementary
+// AAC stream to ADTS).
+class BitstreamConverter
+    : public base::RefCountedThreadSafe<BitstreamConverter> {
+ public:
+  // Converts a single frame/buffer |frame_buf| into the output format.
+  // Returns true iff the conversion was successful.
+  // |frame_buf| is an input/output parameter, it contains input frame data and
+  // contains converted output data if conversion was successful.
+  // |is_keyframe| indicates whether it's a key frame or not.
+  // |subsamples| is an input/output parameter that contains CENC subsample
+  // information. The conversion code should |subsamples| to determine if parts
+  // of input frame are encrypted and should update |subsamples| if necessary,
+  // to make sure it correctly describes the converted output frame. See
+  // SubsampleEntry definition in media/base/decrypt_config.h for more info.
+  virtual bool ConvertFrame(std::vector<uint8>* frame_buf,
+                            bool is_keyframe,
+                            std::vector<SubsampleEntry>* subsamples) const = 0;
+ protected:
+  friend class base::RefCountedThreadSafe<BitstreamConverter>;
+  virtual ~BitstreamConverter();
+};
+
+}  // namespace mp4
+}  // namespace media
+
+#endif  // MEDIA_FORMATS_MP4_AVC_H_