1 files changed, 97 insertions, 0 deletions
diff --git a/dom/media/AudioCaptureTrack.cpp b/dom/media/AudioCaptureTrack.cpp
new file mode 100644
index 0000000000..0a7aaccb5c
--- /dev/null
+++ b/dom/media/AudioCaptureTrack.cpp
@@ -0,0 +1,97 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-*/
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "MediaTrackGraph.h"
+#include "MediaTrackListener.h"
+#include "mozilla/MathAlgorithms.h"
+#include "mozilla/Unused.h"
+
+#include "AudioSegment.h"
+#include "mozilla/Logging.h"
+#include "mozilla/Attributes.h"
+#include "AudioCaptureTrack.h"
+#include "ImageContainer.h"
+#include "AudioNodeEngine.h"
+#include "AudioNodeTrack.h"
+#include "AudioNodeExternalInputTrack.h"
+#include "webaudio/MediaStreamAudioDestinationNode.h"
+#include <algorithm>
+#include "DOMMediaStream.h"
+
+using namespace mozilla::layers;
+using namespace mozilla::dom;
+using namespace mozilla::gfx;
+
+namespace mozilla {
+
+// We are mixing to mono until PeerConnection can accept stereo
+static const uint32_t MONO = 1;
+
+AudioCaptureTrack::AudioCaptureTrack(TrackRate aRate)
+    : ProcessedMediaTrack(aRate, MediaSegment::AUDIO, new AudioSegment()),
+      mStarted(false) {
+  MOZ_ASSERT(NS_IsMainThread());
+  MOZ_COUNT_CTOR(AudioCaptureTrack);
+}
+
+AudioCaptureTrack::~AudioCaptureTrack() { MOZ_COUNT_DTOR(AudioCaptureTrack); }
+
+void AudioCaptureTrack::Start() {
+  QueueControlMessageWithNoShutdown(
+      [self = RefPtr{this}, this] { mStarted = true; });
+}
+
+void AudioCaptureTrack::ProcessInput(GraphTime aFrom, GraphTime aTo,
+                                     uint32_t aFlags) {
+  if (!mStarted) {
+    return;
+  }
+
+  uint32_t inputCount = mInputs.Length();
+
+  if (mEnded) {
+    return;
+  }
+
+  // If the captured track is connected back to a object on the page (be it an
+  // HTMLMediaElement with a track as source, or an AudioContext), a cycle
+  // situation occur. This can work if it's an AudioContext with at least one
+  // DelayNode, but the MTG will mute the whole cycle otherwise.
+  if (InMutedCycle() || inputCount == 0) {
+    GetData<AudioSegment>()->AppendNullData(aTo - aFrom);
+  } else {
+    // We mix down all the tracks of all inputs, to a stereo track. Everything
+    // is {up,down}-mixed to stereo.
+    mMixer.StartMixing();
+    AudioSegment output;
+    for (uint32_t i = 0; i < inputCount; i++) {
+      MediaTrack* s = mInputs[i]->GetSource();
+      AudioSegment* inputSegment = s->GetData<AudioSegment>();
+      TrackTime inputStart = s->GraphTimeToTrackTimeWithBlocking(aFrom);
+      TrackTime inputEnd = s->GraphTimeToTrackTimeWithBlocking(aTo);
+      AudioSegment toMix;
+      if (s->Ended() && inputSegment->GetDuration() <= inputStart) {
+        toMix.AppendNullData(aTo - aFrom);
+      } else {
+        toMix.AppendSlice(*inputSegment, inputStart, inputEnd);
+        // Care for tracks blocked in the [aTo, aFrom] range.
+        if (inputEnd - inputStart < aTo - aFrom) {
+          toMix.AppendNullData((aTo - aFrom) - (inputEnd - inputStart));
+        }
+      }
+      toMix.Mix(mMixer, MONO, Graph()->GraphRate());
+    }
+    AudioChunk* mixed = mMixer.MixedChunk();
+    MOZ_ASSERT(mixed->ChannelCount() == MONO);
+    // Now we have mixed data, simply append it.
+    GetData<AudioSegment>()->AppendAndConsumeChunk(std::move(*mixed));
+  }
+}
+
+uint32_t AudioCaptureTrack::NumberOfChannels() const {
+  return GetData<AudioSegment>()->MaxChannelCount();
+}
+
+}  // namespace mozilla