dom/media/AudioCaptureTrack.cpp

   1 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
   2 /* This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
   4  * You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "MediaTrackGraph.h"
   7 #include "MediaTrackListener.h"
   8 #include "mozilla/MathAlgorithms.h"
   9 #include "mozilla/Unused.h"
  10
  11 #include "AudioSegment.h"
  12 #include "mozilla/Logging.h"
  13 #include "mozilla/Attributes.h"
  14 #include "AudioCaptureTrack.h"
  15 #include "ImageContainer.h"
  16 #include "AudioNodeEngine.h"
  17 #include "AudioNodeTrack.h"
  18 #include "AudioNodeExternalInputTrack.h"
  19 #include "webaudio/MediaStreamAudioDestinationNode.h"
  20 #include <algorithm>
  21 #include "DOMMediaStream.h"
  22
  23 using namespace mozilla::layers;
  24 using namespace mozilla::dom;
  25 using namespace mozilla::gfx;
  26
  27 namespace mozilla {
  28
  29 // We are mixing to mono until PeerConnection can accept stereo
  30 static const uint32_t MONO = 1;
  31
  32 AudioCaptureTrack::AudioCaptureTrack(TrackRate aRate)
  33     : ProcessedMediaTrack(aRate, MediaSegment::AUDIO, new AudioSegment()),
  34       mStarted(false) {
  35   MOZ_ASSERT(NS_IsMainThread());
  36   MOZ_COUNT_CTOR(AudioCaptureTrack);
  37 }
  38
  39 AudioCaptureTrack::~AudioCaptureTrack() { MOZ_COUNT_DTOR(AudioCaptureTrack); }
  40
  41 void AudioCaptureTrack::Start() {
  42   QueueControlMessageWithNoShutdown(
  43       [self = RefPtr{this}, this] { mStarted = true; });
  44 }
  45
  46 void AudioCaptureTrack::ProcessInput(GraphTime aFrom, GraphTime aTo,
  47                                      uint32_t aFlags) {
  48   if (!mStarted) {
  49     return;
  50   }
  51
  52   uint32_t inputCount = mInputs.Length();
  53
  54   if (mEnded) {
  55     return;
  56   }
  57
  58   // If the captured track is connected back to a object on the page (be it an
  59   // HTMLMediaElement with a track as source, or an AudioContext), a cycle
  60   // situation occur. This can work if it's an AudioContext with at least one
  61   // DelayNode, but the MTG will mute the whole cycle otherwise.
  62   if (InMutedCycle() || inputCount == 0) {
  63     GetData<AudioSegment>()->AppendNullData(aTo - aFrom);
  64   } else {
  65     // We mix down all the tracks of all inputs, to a stereo track. Everything
  66     // is {up,down}-mixed to stereo.
  67     mMixer.StartMixing();
  68     AudioSegment output;
  69     for (uint32_t i = 0; i < inputCount; i++) {
  70       MediaTrack* s = mInputs[i]->GetSource();
  71       AudioSegment* inputSegment = s->GetData<AudioSegment>();
  72       TrackTime inputStart = s->GraphTimeToTrackTimeWithBlocking(aFrom);
  73       TrackTime inputEnd = s->GraphTimeToTrackTimeWithBlocking(aTo);
  74       AudioSegment toMix;
  75       if (s->Ended() && inputSegment->GetDuration() <= inputStart) {
  76         toMix.AppendNullData(aTo - aFrom);
  77       } else {
  78         toMix.AppendSlice(*inputSegment, inputStart, inputEnd);
  79         // Care for tracks blocked in the [aTo, aFrom] range.
  80         if (inputEnd - inputStart < aTo - aFrom) {
  81           toMix.AppendNullData((aTo - aFrom) - (inputEnd - inputStart));
  82         }
  83       }
  84       toMix.Mix(mMixer, MONO, Graph()->GraphRate());
  85     }
  86     AudioChunk* mixed = mMixer.MixedChunk();
  87     MOZ_ASSERT(mixed->ChannelCount() == MONO);
  88     // Now we have mixed data, simply append it.
  89     GetData<AudioSegment>()->AppendAndConsumeChunk(std::move(*mixed));
  90   }
  91 }
  92
  93 uint32_t AudioCaptureTrack::NumberOfChannels() const {
  94   return GetData<AudioSegment>()->MaxChannelCount();
  95 }
  96
  97 }  // namespace mozilla