media/capture: Adding WebmMuxer class and unittests

media/capture/webm_muxer.h

+// 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_FILTERS_LIBWEBM_MUXER_H_
+#define MEDIA_FILTERS_LIBWEBM_MUXER_H_
+
+#include <set>
+
+#include "base/callback.h"
+#include "base/gtest_prod_util.h"
+#include "base/numerics/safe_math.h"
+#include "base/threading/thread_checker.h"
+#include "base/time/time.h"
+#include "media/base/media_export.h"
+#include "third_party/libwebm/source/mkvmuxer.hpp"
+#include "ui/gfx/geometry/size.h"
+
+namespace media {
+
+// Adapter class to manage a WebM container, a simplified version of a Matroska
+// container [1], composed of an EBML header, and a single Segment including
+// at least a Track Section and a number of SimpleBlocks each containing a
+// single encoded video frame. WebM container has no Trailer.
+// Clients will push encoded VPx video frames one by one via OnEncodedVideo()
+// with indication of the Track they belong to, and libwebm will eventually ping
+// the WriteDataCB passed on contructor with the wrapped encoded data. All
+// operations must happen in a single thread, where WebmMuxer is created and
+// destroyed.
+// [1] http://www.matroska.org/technical/specs/index.html
+// TODO(mcasas): Add support for Audio muxing.
+class MEDIA_EXPORT WebmMuxer : public mkvmuxer::IMkvWriter {
+ public:
+  // Callback to be called when WebmMuxer is ready to write a chunk of data,
+  // either any file header or a SingleBlock. The chunk is described as a byte
+  // array and a byte length.
+  typedef base::Callback<void(const char*, size_t)> WriteDataCB;
+
+  explicit WebmMuxer(const WriteDataCB& write_data_callback);
+  ~WebmMuxer() override;
+
+  // Creates and adds a new video track. Called before receiving the first
+  // frame of a given Track, adds |frame_size| and |frame_rate| to the Segment
+  // info, although individual frames passed to OnEncodedVideo() can have any
+  // frame size.
+  void AddVideoTrack(uint32_t track_number,
+                     const gfx::Size& frame_size,
+                     double frame_rate);
+
+  // Adds a frame with |encoded_data.data()| to WebM Segment. |track_number| is
+  // a caller-side identifier and must have been AddVideoTrack()ed before.
+  void OnEncodedVideo(uint32_t track_number,
+                      const std::string& encoded_data,
+                      const base::TimeDelta& timestamp,
+                      bool keyframe);
+
+ private:
+  friend class WebmMuxerTest;

[DaleCurtis, 2015/07/20 18:45:17]

Why both this and the FRIEND_TEST....

[mcasas, 2015/07/20 20:15:20]

Both are needed for the individual tests to access
private members (note that tests are subclasses).
I figured is better to add the macro than add an
accessor, that increases the whole class footprint.

[DaleCurtis, 2015/07/20 20:23:07]

Just add accessors to the WebmMuxerTest harness. I loath FRIEND_TEST_ALL :)

[mcasas, 2015/07/21 12:56:20]

Done.

+  FRIEND_TEST_ALL_PREFIXES(WebmMuxerTest, AddVideoTrack);
+  FRIEND_TEST_ALL_PREFIXES(WebmMuxerTest, Write);
+  FRIEND_TEST_ALL_PREFIXES(WebmMuxerTest, OnEncodedVideoEmptyAndNormalFrames);
+  FRIEND_TEST_ALL_PREFIXES(WebmMuxerTest, OnEncodedVideoNormalFrames);
+
+  // IMkvWriter interface.
+  mkvmuxer::int32 Write(const void* buf, mkvmuxer::uint32 len) override;
+  mkvmuxer::int64 Position() const override;
+  mkvmuxer::int32 Position(mkvmuxer::int64 position) override;
+  bool Seekable() const override;
+  void ElementStartNotify(mkvmuxer::uint64 element_id,
+                          mkvmuxer::int64 position) override;
+
+  // Used to DCHECK that we are called on the correct thread.
+  base::ThreadChecker thread_checker_;
+
+  // Callback to dump written data as being called by libwebm.
+  const WriteDataCB write_data_callback_;
+
+  // Rolling counter of the position in bytes of the written goo.
+  base::CheckedNumeric<mkvmuxer::int64> position_;
+
+  // Owned pointer to the MkvMuxer active element.
+  const scoped_ptr<mkvmuxer::Segment> segment_;

[DaleCurtis, 2015/07/20 18:45:17]

Why const scoped_ptr? Just use a mkvmuxer::Segment directly here?

[mcasas, 2015/07/20 20:15:20]

Done.

+
+  DISALLOW_COPY_AND_ASSIGN(WebmMuxer);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_FILTERS_LIBWEBM_MUXER_H_