media/capture: Adding WebmMuxer class and unittests

media/capture/webm_muxer.cc

+// 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.
+
+#include "media/capture/webm_muxer.h"
+
+#include <limits>
+
+namespace media {
+
+WebmMuxer::WebmMuxer(const WriteDataCB& write_data_callback)
+    : write_data_callback_(write_data_callback),
+      position_(0) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  segment_.Init(this);
+  segment_.set_mode(mkvmuxer::Segment::kLive);
+  segment_.OutputCues(false);
+
+  mkvmuxer::SegmentInfo* const info = segment_.GetSegmentInfo();
+  info->set_writing_app("Chrome");
+  info->set_muxing_app("Chrome");
+}
+
+WebmMuxer::~WebmMuxer() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  segment_.Finalize();
+}
+
+uint64_t WebmMuxer::AddVideoTrack(const gfx::Size& frame_size,
+                                  double frame_rate) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+
+  const uint64_t track_index =
+      segment_.AddVideoTrack(frame_size.width(), frame_size.height(), 0);
+
+  mkvmuxer::VideoTrack* const video_track =
+      reinterpret_cast<mkvmuxer::VideoTrack*>(
+          segment_.GetTrackByNumber(track_index));
+  DCHECK(video_track);
+  video_track->set_codec_id(mkvmuxer::Tracks::kVp8CodecId);
+  DCHECK_EQ(video_track->crop_right(), 0ull);
+  DCHECK_EQ(video_track->crop_left(), 0ull);
+  DCHECK_EQ(video_track->crop_top(), 0ull);
+  DCHECK_EQ(video_track->crop_bottom(), 0ull);
+
+  video_track->set_frame_rate(frame_rate);
+  video_track->set_default_duration(base::Time::kMicrosecondsPerSecond /
+                                    frame_rate);
+  // Segment's timestamps should be in milliseconds, dcheck it. See
+  // http://www.webmproject.org/docs/container/#muxer-guidelines
+  DCHECK_EQ(segment_.GetSegmentInfo()->timecode_scale(), 1000000ull);
+
+  return track_index;
+}
+
+void WebmMuxer::OnEncodedVideo(uint64_t track_number,
+                               const uint8_t* encoded_data,
+                               size_t encoded_data_len,
+                               const base::TimeDelta& timestamp,
+                               bool keyframe) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  // |track_number|, a caller-side identifier, cannot be zero (!), see
+  // http://www.matroska.org/technical/specs/index.html#Tracks
+  DCHECK_GT(track_number, 0u);
+  DCHECK(segment_.GetTrackByNumber(track_number));
+
+  segment_.AddFrame(encoded_data, encoded_data_len, track_number,
+                    timestamp.InMilliseconds(), keyframe);
+}
+
+mkvmuxer::int32 WebmMuxer::Write(const void* buf, mkvmuxer::uint32 len) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  write_data_callback_.Run(static_cast<const char*>(buf), len);
+  position_ += len;
+  return 0;

[DaleCurtis, 2015/07/21 16:52:30]

Is this the right return value, generally a Write() returns the number of bytes
written.

[mcasas, 2015/07/21 19:46:59]

[1] "returns 0 on success"

[1] https://code.google.com/p/webm/source/browse/mkvmuxer.hpp?repo=libwebm&#32

+}
+
+mkvmuxer::int64 WebmMuxer::Position() const {
+  return position_.ValueOrDie();
+}
+
+mkvmuxer::int32 WebmMuxer::Position(mkvmuxer::int64 position) {
+  // The stream is not Seekable() so indicate we cannot set the position.

[DaleCurtis, 2015/07/21 16:52:30]

Does NOTREACHED() get hit?

[mcasas, 2015/07/21 19:46:59]

I doubt it, because the stream is "Live".
Returning 0 would mean success. [1]

[1] https://code.google.com/p/webm/source/browse/mkvmuxer.hpp?repo=libwebm&#39

+  return -1;
+}
+
+bool WebmMuxer::Seekable() const {
+  return false;
+}
+
+void WebmMuxer::ElementStartNotify(mkvmuxer::uint64 element_id,
+                                   mkvmuxer::int64 position) {
+  // This method gets pinged before items are sent to |write_data_callback_|.
+  DCHECK_GE(position, position_.ValueOrDefault(0))
+      << "Can't go back in a Live Mkv stream.";

[DaleCurtis, 2015/07/21 16:52:30]

live webm stream

[mcasas, 2015/07/21 19:46:59]

Done.

+}
+
+}  // namespace media