media/capture/webm_muxer.cc

   1 // Copyright 2015 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "media/capture/webm_muxer.h"
   6
   7 #include <limits>
   8
   9 namespace media {
  10
  11 WebmMuxer::WebmMuxer(const WriteDataCB& write_data_callback)
  12     : write_data_callback_(write_data_callback),
  13       position_(0) {
  14   DCHECK(thread_checker_.CalledOnValidThread());
  15   segment_.Init(this);
  16   segment_.set_mode(mkvmuxer::Segment::kLive);
  17   segment_.OutputCues(false);
  18
  19   mkvmuxer::SegmentInfo* const info = segment_.GetSegmentInfo();
  20   info->set_writing_app("Chrome");
  21   info->set_muxing_app("Chrome");
  22 }
  23
  24 WebmMuxer::~WebmMuxer() {
  25   DCHECK(thread_checker_.CalledOnValidThread());
  26   segment_.Finalize();
  27 }
  28
  29 uint64_t WebmMuxer::AddVideoTrack(const gfx::Size& frame_size,
  30                                   double frame_rate) {
  31   DCHECK(thread_checker_.CalledOnValidThread());
  32
  33   const uint64_t track_index =
  34       segment_.AddVideoTrack(frame_size.width(), frame_size.height(), 0);
  35
  36   mkvmuxer::VideoTrack* const video_track =
  37       reinterpret_cast<mkvmuxer::VideoTrack*>(
  38           segment_.GetTrackByNumber(track_index));
  39   DCHECK(video_track);
  40   video_track->set_codec_id(mkvmuxer::Tracks::kVp8CodecId);
  41   DCHECK_EQ(video_track->crop_right(), 0ull);
  42   DCHECK_EQ(video_track->crop_left(), 0ull);
  43   DCHECK_EQ(video_track->crop_top(), 0ull);
  44   DCHECK_EQ(video_track->crop_bottom(), 0ull);
  45
  46   video_track->set_frame_rate(frame_rate);
  47   video_track->set_default_duration(base::Time::kMicrosecondsPerSecond /
  48                                     frame_rate);
  49   // Segment's timestamps should be in milliseconds, DCHECK it. See
  50   // http://www.webmproject.org/docs/container/#muxer-guidelines
  51   DCHECK_EQ(segment_.GetSegmentInfo()->timecode_scale(), 1000000ull);
  52
  53   return track_index;
  54 }
  55
  56 void WebmMuxer::OnEncodedVideo(uint64_t track_number,
  57                                const base::StringPiece& encoded_data,
  58                                base::TimeDelta timestamp,
  59                                bool keyframe) {
  60   DCHECK(thread_checker_.CalledOnValidThread());
  61   // |track_number|, a caller-side identifier, cannot be zero (!), see
  62   // http://www.matroska.org/technical/specs/index.html#Tracks
  63   DCHECK_GT(track_number, 0u);
  64   DCHECK(segment_.GetTrackByNumber(track_number));
  65
  66   segment_.AddFrame(reinterpret_cast<const uint8_t*>(encoded_data.data()),
  67       encoded_data.size(), track_number, timestamp.InMilliseconds(), keyframe);
  68 }
  69
  70 mkvmuxer::int32 WebmMuxer::Write(const void* buf, mkvmuxer::uint32 len) {
  71   DCHECK(thread_checker_.CalledOnValidThread());
  72   write_data_callback_.Run(base::StringPiece(reinterpret_cast<const char*>(buf),
  73                                              len));
  74   position_ += len;
  75   return 0;
  76 }
  77
  78 mkvmuxer::int64 WebmMuxer::Position() const {
  79   return position_.ValueOrDie();
  80 }
  81
  82 mkvmuxer::int32 WebmMuxer::Position(mkvmuxer::int64 position) {
  83   // The stream is not Seekable() so indicate we cannot set the position.
  84   return -1;
  85 }
  86
  87 bool WebmMuxer::Seekable() const {
  88   return false;
  89 }
  90
  91 void WebmMuxer::ElementStartNotify(mkvmuxer::uint64 element_id,
  92                                    mkvmuxer::int64 position) {
  93   // This method gets pinged before items are sent to |write_data_callback_|.
  94   DCHECK_GE(position, position_.ValueOrDefault(0))
  95       << "Can't go back in a live WebM stream.";
  96 }
  97
  98 }  // namespace media