1 files changed, 315 insertions, 0 deletions
diff --git a/dom/media/webaudio/AudioEventTimeline.cpp b/dom/media/webaudio/AudioEventTimeline.cpp
new file mode 100644
index 000000000..a6a7bbf66
--- /dev/null
+++ b/dom/media/webaudio/AudioEventTimeline.cpp
@@ -0,0 +1,315 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* 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 "AudioEventTimeline.h"
+
+#include "mozilla/ErrorResult.h"
+
+static float LinearInterpolate(double t0, float v0, double t1, float v1, double t)
+{
+  return v0 + (v1 - v0) * ((t - t0) / (t1 - t0));
+}
+
+static float ExponentialInterpolate(double t0, float v0, double t1, float v1, double t)
+{
+  return v0 * powf(v1 / v0, (t - t0) / (t1 - t0));
+}
+
+static float ExponentialApproach(double t0, double v0, float v1, double timeConstant, double t)
+{
+  if (!mozilla::dom::WebAudioUtils::FuzzyEqual(timeConstant, 0.0)) {
+    return v1 + (v0 - v1) * expf(-(t - t0) / timeConstant);
+  } else {
+    return v1;
+  }
+}
+
+static float ExtractValueFromCurve(double startTime, float* aCurve, uint32_t aCurveLength, double duration, double t)
+{
+  if (t >= startTime + duration) {
+    // After the duration, return the last curve value
+    return aCurve[aCurveLength - 1];
+  }
+  double ratio = std::max((t - startTime) / duration, 0.0);
+  if (ratio >= 1.0) {
+    return aCurve[aCurveLength - 1];
+  }
+  uint32_t current = uint32_t(floor((aCurveLength - 1) * ratio));
+  uint32_t next = current + 1;
+  double step = duration / double(aCurveLength - 1);
+  if (next < aCurveLength) {
+    double t0 = current * step;
+    double t1 = next * step;
+    return LinearInterpolate(t0, aCurve[current], t1, aCurve[next], t - startTime);
+  } else {
+    return aCurve[current];
+  }
+}
+
+namespace mozilla {
+namespace dom {
+
+// This method computes the AudioParam value at a given time based on the event timeline
+template<class TimeType> void
+AudioEventTimeline::GetValuesAtTimeHelper(TimeType aTime, float* aBuffer,
+                                          const size_t aSize)
+{
+  MOZ_ASSERT(aBuffer);
+  MOZ_ASSERT(aSize);
+
+  auto TimeOf = [](const AudioTimelineEvent& aEvent) -> TimeType {
+    return aEvent.template Time<TimeType>();
+  };
+
+  size_t eventIndex = 0;
+  const AudioTimelineEvent* previous = nullptr;
+
+  // Let's remove old events except the last one: we need it to calculate some curves.
+  CleanupEventsOlderThan(aTime);
+
+  for (size_t bufferIndex = 0; bufferIndex < aSize; ++bufferIndex, ++aTime) {
+
+    bool timeMatchesEventIndex = false;
+    const AudioTimelineEvent* next;
+    for (; ; ++eventIndex) {
+
+      if (eventIndex >= mEvents.Length()) {
+        next = nullptr;
+        break;
+      }
+
+      next = &mEvents[eventIndex];
+      if (aTime < TimeOf(*next)) {
+        break;
+      }
+
+#ifdef DEBUG
+      MOZ_ASSERT(next->mType == AudioTimelineEvent::SetValueAtTime ||
+                 next->mType == AudioTimelineEvent::SetTarget ||
+                 next->mType == AudioTimelineEvent::LinearRamp ||
+                 next->mType == AudioTimelineEvent::ExponentialRamp ||
+                 next->mType == AudioTimelineEvent::SetValueCurve);
+#endif
+
+      if (TimesEqual(aTime, TimeOf(*next))) {
+        mLastComputedValue = mComputedValue;
+        // Find the last event with the same time
+        while (eventIndex < mEvents.Length() - 1 &&
+               TimesEqual(aTime, TimeOf(mEvents[eventIndex + 1]))) {
+          mLastComputedValue = GetValueAtTimeOfEvent<TimeType>(&mEvents[eventIndex]);
+          ++eventIndex;
+        }
+
+        timeMatchesEventIndex = true;
+        break;
+      }
+
+      previous = next;
+    }
+
+    if (timeMatchesEventIndex) {
+      // The time matches one of the events exactly.
+      MOZ_ASSERT(TimesEqual(aTime, TimeOf(mEvents[eventIndex])));
+      mComputedValue = GetValueAtTimeOfEvent<TimeType>(&mEvents[eventIndex]);
+    } else {
+      mComputedValue = GetValuesAtTimeHelperInternal(aTime, previous, next);
+    }
+
+    aBuffer[bufferIndex] = mComputedValue;
+  }
+}
+template void
+AudioEventTimeline::GetValuesAtTimeHelper(double aTime, float* aBuffer,
+                                          const size_t aSize);
+template void
+AudioEventTimeline::GetValuesAtTimeHelper(int64_t aTime, float* aBuffer,
+                                          const size_t aSize);
+
+template<class TimeType> float
+AudioEventTimeline::GetValueAtTimeOfEvent(const AudioTimelineEvent* aNext)
+{
+  TimeType time = aNext->template Time<TimeType>();
+  switch (aNext->mType) {
+    case AudioTimelineEvent::SetTarget:
+      // SetTarget nodes can be handled no matter what their next node is
+      // (if they have one).
+      // Follow the curve, without regard to the next event, starting at
+      // the last value of the last event.
+      return ExponentialApproach(time,
+                                 mLastComputedValue, aNext->mValue,
+                                 aNext->mTimeConstant, time);
+      break;
+    case AudioTimelineEvent::SetValueCurve:
+      // SetValueCurve events can be handled no matter what their event
+      // node is (if they have one)
+      return ExtractValueFromCurve(time,
+                                   aNext->mCurve,
+                                   aNext->mCurveLength,
+                                   aNext->mDuration, time);
+      break;
+    default:
+      // For other event types
+      return aNext->mValue;
+  }
+}
+
+template<class TimeType> float
+AudioEventTimeline::GetValuesAtTimeHelperInternal(TimeType aTime,
+                                    const AudioTimelineEvent* aPrevious,
+                                    const AudioTimelineEvent* aNext)
+{
+  // If the requested time is before all of the existing events
+  if (!aPrevious) {
+     return mValue;
+  }
+
+  auto TimeOf = [](const AudioTimelineEvent* aEvent) -> TimeType {
+    return aEvent->template Time<TimeType>();
+  };
+
+  // SetTarget nodes can be handled no matter what their next node is (if
+  // they have one)
+  if (aPrevious->mType == AudioTimelineEvent::SetTarget) {
+    return ExponentialApproach(TimeOf(aPrevious),
+                               mLastComputedValue, aPrevious->mValue,
+                               aPrevious->mTimeConstant, aTime);
+  }
+
+  // SetValueCurve events can be handled no matter what their next node is
+  // (if they have one)
+  if (aPrevious->mType == AudioTimelineEvent::SetValueCurve) {
+    return ExtractValueFromCurve(TimeOf(aPrevious),
+                                 aPrevious->mCurve, aPrevious->mCurveLength,
+                                 aPrevious->mDuration, aTime);
+  }
+
+  // If the requested time is after all of the existing events
+  if (!aNext) {
+    switch (aPrevious->mType) {
+      case AudioTimelineEvent::SetValueAtTime:
+      case AudioTimelineEvent::LinearRamp:
+      case AudioTimelineEvent::ExponentialRamp:
+        // The value will be constant after the last event
+        return aPrevious->mValue;
+      case AudioTimelineEvent::SetValueCurve:
+        return ExtractValueFromCurve(TimeOf(aPrevious),
+                                     aPrevious->mCurve, aPrevious->mCurveLength,
+                                     aPrevious->mDuration, aTime);
+      case AudioTimelineEvent::SetTarget:
+        MOZ_FALLTHROUGH_ASSERT("AudioTimelineEvent::SetTarget");
+      case AudioTimelineEvent::SetValue:
+      case AudioTimelineEvent::Cancel:
+      case AudioTimelineEvent::Stream:
+        MOZ_ASSERT(false, "Should have been handled earlier.");
+    }
+    MOZ_ASSERT(false, "unreached");
+  }
+
+  // Finally, handle the case where we have both a previous and a next event
+
+  // First, handle the case where our range ends up in a ramp event
+  switch (aNext->mType) {
+  case AudioTimelineEvent::LinearRamp:
+    return LinearInterpolate(TimeOf(aPrevious),
+                             aPrevious->mValue,
+                             TimeOf(aNext),
+                             aNext->mValue, aTime);
+
+  case AudioTimelineEvent::ExponentialRamp:
+    return ExponentialInterpolate(TimeOf(aPrevious),
+                                  aPrevious->mValue,
+                                  TimeOf(aNext),
+                                  aNext->mValue, aTime);
+
+  case AudioTimelineEvent::SetValueAtTime:
+  case AudioTimelineEvent::SetTarget:
+  case AudioTimelineEvent::SetValueCurve:
+    break;
+  case AudioTimelineEvent::SetValue:
+  case AudioTimelineEvent::Cancel:
+  case AudioTimelineEvent::Stream:
+    MOZ_ASSERT(false, "Should have been handled earlier.");
+  }
+
+  // Now handle all other cases
+  switch (aPrevious->mType) {
+  case AudioTimelineEvent::SetValueAtTime:
+  case AudioTimelineEvent::LinearRamp:
+  case AudioTimelineEvent::ExponentialRamp:
+    // If the next event type is neither linear or exponential ramp, the
+    // value is constant.
+    return aPrevious->mValue;
+  case AudioTimelineEvent::SetValueCurve:
+    return ExtractValueFromCurve(TimeOf(aPrevious),
+                                 aPrevious->mCurve, aPrevious->mCurveLength,
+                                 aPrevious->mDuration, aTime);
+  case AudioTimelineEvent::SetTarget:
+    MOZ_FALLTHROUGH_ASSERT("AudioTimelineEvent::SetTarget");
+  case AudioTimelineEvent::SetValue:
+  case AudioTimelineEvent::Cancel:
+  case AudioTimelineEvent::Stream:
+    MOZ_ASSERT(false, "Should have been handled earlier.");
+  }
+
+  MOZ_ASSERT(false, "unreached");
+  return 0.0f;
+}
+template float
+AudioEventTimeline::GetValuesAtTimeHelperInternal(double aTime,
+                                    const AudioTimelineEvent* aPrevious,
+                                    const AudioTimelineEvent* aNext);
+template float
+AudioEventTimeline::GetValuesAtTimeHelperInternal(int64_t aTime,
+                                    const AudioTimelineEvent* aPrevious,
+                                    const AudioTimelineEvent* aNext);
+
+const AudioTimelineEvent*
+AudioEventTimeline::GetPreviousEvent(double aTime) const
+{
+  const AudioTimelineEvent* previous = nullptr;
+  const AudioTimelineEvent* next = nullptr;
+
+  auto TimeOf = [](const AudioTimelineEvent& aEvent) -> double {
+    return aEvent.template Time<double>();
+  };
+
+  bool bailOut = false;
+  for (unsigned i = 0; !bailOut && i < mEvents.Length(); ++i) {
+    switch (mEvents[i].mType) {
+    case AudioTimelineEvent::SetValueAtTime:
+    case AudioTimelineEvent::SetTarget:
+    case AudioTimelineEvent::LinearRamp:
+    case AudioTimelineEvent::ExponentialRamp:
+    case AudioTimelineEvent::SetValueCurve:
+      if (aTime == TimeOf(mEvents[i])) {
+        // Find the last event with the same time
+        do {
+          ++i;
+        } while (i < mEvents.Length() &&
+                 aTime == TimeOf(mEvents[i]));
+        return &mEvents[i - 1];
+      }
+      previous = next;
+      next = &mEvents[i];
+      if (aTime < TimeOf(mEvents[i])) {
+        bailOut = true;
+      }
+      break;
+    default:
+      MOZ_ASSERT(false, "unreached");
+    }
+  }
+  // Handle the case where the time is past all of the events
+  if (!bailOut) {
+    previous = next;
+  }
+
+  return previous;
+}
+
+} // namespace dom
+} // namespace mozilla
+