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diff --git a/dom/media/TimeUnits.h b/dom/media/TimeUnits.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* 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/. */
+
+#ifndef TIME_UNITS_H
+#define TIME_UNITS_H
+
+#include <limits>
+#include <type_traits>
+
+#include "Intervals.h"
+#include "mozilla/CheckedInt.h"
+#include "mozilla/FloatingPoint.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/TimeStamp.h"
+#include "mozilla/IntegerPrintfMacros.h"
+#include "nsPrintfCString.h"
+
+namespace mozilla::media {
+class TimeIntervals;
+}  // namespace mozilla::media
+// CopyChooser specialization for nsTArray
+template <>
+struct nsTArray_RelocationStrategy<mozilla::media::TimeIntervals> {
+  using Type =
+      nsTArray_RelocateUsingMoveConstructor<mozilla::media::TimeIntervals>;
+};
+
+namespace mozilla {
+
+// Number of milliseconds per second. 1e3.
+static const int64_t MSECS_PER_S = 1000;
+
+// Number of microseconds per second. 1e6.
+static const int64_t USECS_PER_S = 1000000;
+
+// Number of nanoseconds per second. 1e9.
+static const int64_t NSECS_PER_S = 1000000000;
+
+namespace media {
+
+#ifndef PROCESS_DECODE_LOG
+#  define PROCESS_DECODE_LOG(sample)                                   \
+    MOZ_LOG(sPDMLog, mozilla::LogLevel::Verbose,                       \
+            ("ProcessDecode: mDuration=%" PRIu64 "µs ; mTime=%" PRIu64 \
+             "µs ; mTimecode=%" PRIu64 "µs",                           \
+             (sample)->mDuration.ToMicroseconds(),                     \
+             (sample)->mTime.ToMicroseconds(),                         \
+             (sample)->mTimecode.ToMicroseconds()))
+#endif  // PROCESS_DECODE_LOG
+
+// TimeUnit is a class that represents a time value, that can be negative or
+// positive.
+//
+// Internally, it works by storing a numerator (the tick numbers), that uses
+// checked arithmetics, and a denominator (the base), that is a regular integer
+// on which arithmetics is never performed, and is only set at construction, or
+// replaced.
+//
+// Dividing the tick count by the base always yields a value in seconds,
+// but it's very useful to have a base that is dependant on the context: it can
+// be the sample-rate of an audio stream, the time base of an mp4, that's often
+// 90000 because it's divisible by 24, 25 and 30.
+//
+// Keeping time like this allows performing calculations on time values with
+// maximum precision, without having to have to care about rounding errors or
+// precision loss.
+//
+// If not specified, the base is 1e6, representing microseconds, for historical
+// reasons. Users can gradually move to more precise representations when
+// needed.
+//
+// INT64_MAX has the special meaning of being +∞, and INT64_MIN means -∞. Any
+// other value corresponds to a valid time.
+//
+// If an overflow or other problem occurs, the underlying CheckedInt<int64_t> is
+// invalid and a crash is triggered.
+class TimeUnit final {
+ public:
+  constexpr TimeUnit(CheckedInt64 aTicks, int64_t aBase)
+      : mTicks(aTicks), mBase(aBase) {
+    MOZ_RELEASE_ASSERT(mBase > 0);
+  }
+
+  explicit constexpr TimeUnit(CheckedInt64 aTicks)
+      : mTicks(aTicks), mBase(USECS_PER_S) {}
+
+  // Return the maximum number of ticks that a TimeUnit can contain.
+  static constexpr int64_t MaxTicks() {
+    return std::numeric_limits<int64_t>::max() - 1;
+  }
+
+  // This is only precise up to a point, which is aValue * aBase <= 2^53 - 1
+  static TimeUnit FromSeconds(double aValue, int64_t aBase = USECS_PER_S);
+  static constexpr TimeUnit FromMicroseconds(int64_t aValue) {
+    return TimeUnit(aValue, USECS_PER_S);
+  }
+  static TimeUnit FromHns(int64_t aValue, int64_t aBase) {
+    // Truncating here would mean a loss of precision.
+    return TimeUnit::FromNanoseconds(aValue * 100).ToBase<RoundPolicy>(aBase);
+  }
+  static constexpr TimeUnit FromNanoseconds(int64_t aValue) {
+    return TimeUnit(aValue, NSECS_PER_S);
+  }
+  static TimeUnit FromInfinity();
+  static TimeUnit FromNegativeInfinity();
+  static TimeUnit FromTimeDuration(const TimeDuration& aDuration);
+  static constexpr TimeUnit Zero(int64_t aBase = USECS_PER_S) {
+    return TimeUnit(0, aBase);
+  }
+  static constexpr TimeUnit Zero(const TimeUnit& aOther) {
+    return TimeUnit(0, aOther.mBase);
+  }
+  static TimeUnit Invalid();
+  int64_t ToMilliseconds() const;
+  int64_t ToMicroseconds() const;
+  int64_t ToNanoseconds() const;
+  int64_t ToTicksAtRate(int64_t aRate) const;
+  // Only to be used in release assertions or unit testing, returns true if this
+  // TimeUnit has base aBase
+  bool IsBase(int64_t aBase) const;
+  double ToSeconds() const;
+  nsCString ToString() const;
+  TimeDuration ToTimeDuration() const;
+  bool IsInfinite() const;
+  bool IsPositive() const;
+  bool IsPositiveOrZero() const;
+  bool IsZero() const;
+  bool IsNegative() const;
+
+  // Returns true if the fractions are equal when converted to the smallest
+  // base.
+  bool EqualsAtLowestResolution(const TimeUnit& aOther) const;
+  // Strict equality -- the fractions must be exactly equal
+  bool operator==(const TimeUnit& aOther) const;
+  bool operator!=(const TimeUnit& aOther) const;
+  bool operator>=(const TimeUnit& aOther) const;
+  bool operator>(const TimeUnit& aOther) const;
+  bool operator<=(const TimeUnit& aOther) const;
+  bool operator<(const TimeUnit& aOther) const;
+  TimeUnit operator%(const TimeUnit& aOther) const;
+  TimeUnit operator+(const TimeUnit& aOther) const;
+  TimeUnit operator-(const TimeUnit& aOther) const;
+  TimeUnit& operator+=(const TimeUnit& aOther);
+  TimeUnit& operator-=(const TimeUnit& aOther);
+  template <typename T>
+  TimeUnit operator*(T aVal) const {
+    // See bug 853398 for the reason to block double multiplier.
+    // If required, use MultDouble below and with caution.
+    static_assert(std::is_integral_v<T>, "Must be an integral type");
+    return TimeUnit(mTicks * aVal, mBase);
+  }
+  TimeUnit MultDouble(double aVal) const;
+  friend TimeUnit operator/(const TimeUnit& aUnit, int64_t aVal) {
+    MOZ_DIAGNOSTIC_ASSERT(0 <= aVal && aVal <= UINT32_MAX);
+    return TimeUnit(aUnit.mTicks / aVal, aUnit.mBase);
+  }
+  friend TimeUnit operator%(const TimeUnit& aUnit, int64_t aVal) {
+    MOZ_DIAGNOSTIC_ASSERT(0 <= aVal && aVal <= UINT32_MAX);
+    return TimeUnit(aUnit.mTicks % aVal, aUnit.mBase);
+  }
+
+  struct TruncatePolicy {
+    template <typename T>
+    static T policy(T& aValue) {
+      return static_cast<T>(aValue);
+    }
+  };
+
+  struct RoundPolicy {
+    template <typename T>
+    static T policy(T& aValue) {
+      return std::round(aValue);
+    }
+  };
+
+  struct CeilingPolicy {
+    template <typename T>
+    static T policy(T& aValue) {
+      return std::ceil(aValue);
+    }
+  };
+
+  template <class RoundingPolicy = TruncatePolicy>
+  TimeUnit ToBase(int64_t aTargetBase) const {
+    double dummy = 0.0;
+    return ToBase<RoundingPolicy>(aTargetBase, dummy);
+  }
+
+  template <class RoundingPolicy = TruncatePolicy>
+  TimeUnit ToBase(const TimeUnit& aTimeUnit) const {
+    double dummy = 0.0;
+    return ToBase<RoundingPolicy>(aTimeUnit, dummy);
+  }
+
+  // Allow returning the same value, in a base that matches another TimeUnit.
+  template <class RoundingPolicy = TruncatePolicy>
+  TimeUnit ToBase(const TimeUnit& aTimeUnit, double& aOutError) const {
+    int64_t targetBase = aTimeUnit.mBase;
+    return ToBase<RoundingPolicy>(targetBase, aOutError);
+  }
+
+  template <class RoundingPolicy = TruncatePolicy>
+  TimeUnit ToBase(int64_t aTargetBase, double& aOutError) const {
+    aOutError = 0.0;
+    CheckedInt<int64_t> ticks = mTicks * aTargetBase;
+    if (ticks.isValid()) {
+      imaxdiv_t rv = imaxdiv(ticks.value(), mBase);
+      if (!rv.rem) {
+        return TimeUnit(rv.quot, aTargetBase);
+      }
+    }
+    double approx = static_cast<double>(mTicks.value()) *
+                    static_cast<double>(aTargetBase) /
+                    static_cast<double>(mBase);
+    double integer;
+    aOutError = modf(approx, &integer);
+    return TimeUnit(AssertedCast<int64_t>(RoundingPolicy::policy(approx)),
+                    aTargetBase);
+  }
+
+  bool IsValid() const;
+
+  constexpr TimeUnit() = default;
+
+  TimeUnit(const TimeUnit&) = default;
+
+  TimeUnit& operator=(const TimeUnit&) = default;
+
+  bool IsPosInf() const;
+  bool IsNegInf() const;
+
+  // Allow serializing a TimeUnit via IPC
+  friend IPC::ParamTraits<mozilla::media::TimeUnit>;
+
+#ifndef VISIBLE_TIMEUNIT_INTERNALS
+ private:
+#endif
+  int64_t ToCommonUnit(int64_t aRatio) const;
+  // Reduce a TimeUnit to the smallest possible ticks and base. This is useful
+  // to comparison with big time values that can otherwise overflow.
+  TimeUnit Reduced() const;
+
+  CheckedInt64 mTicks{0};
+  // Default base is microseconds.
+  int64_t mBase{USECS_PER_S};
+};
+
+using NullableTimeUnit = Maybe<TimeUnit>;
+
+using TimeInterval = Interval<TimeUnit>;
+
+// A set of intervals, containing TimeUnit.
+class TimeIntervals : public IntervalSet<TimeUnit> {
+ public:
+  using BaseType = IntervalSet<TimeUnit>;
+  using InnerType = TimeUnit;
+
+  // We can't use inherited constructors yet. So we have to duplicate all the
+  // constructors found in IntervalSet base class.
+  // all this could be later replaced with:
+  // using IntervalSet<TimeUnit>::IntervalSet;
+
+  // MOZ_IMPLICIT as we want to enable initialization in the form:
+  // TimeIntervals i = ... like we would do with IntervalSet<T> i = ...
+  MOZ_IMPLICIT TimeIntervals(const BaseType& aOther) : BaseType(aOther) {}
+  MOZ_IMPLICIT TimeIntervals(BaseType&& aOther) : BaseType(std::move(aOther)) {}
+  explicit TimeIntervals(const BaseType::ElemType& aOther) : BaseType(aOther) {}
+  explicit TimeIntervals(BaseType::ElemType&& aOther)
+      : BaseType(std::move(aOther)) {}
+
+  static TimeIntervals Invalid() {
+    return TimeIntervals(TimeInterval(TimeUnit::FromNegativeInfinity(),
+                                      TimeUnit::FromNegativeInfinity()));
+  }
+  bool IsInvalid() const {
+    return Length() == 1 && Start(0).IsNegInf() && End(0).IsNegInf();
+  }
+
+  // Returns the same interval, with a given base resolution.
+  TimeIntervals ToBase(const TimeUnit& aBase) const {
+    TimeIntervals output;
+    for (const auto& interval : mIntervals) {
+      TimeInterval convertedInterval{interval.mStart.ToBase(aBase),
+                                     interval.mEnd.ToBase(aBase),
+                                     interval.mFuzz.ToBase(aBase)};
+      output += convertedInterval;
+    }
+    return output;
+  }
+
+  // Returns the same interval, with a microsecond resolution. This is used to
+  // compare TimeUnits internal to demuxers (that use a base from the container)
+  // to floating point numbers in seconds from content.
+  TimeIntervals ToMicrosecondResolution() const {
+    TimeIntervals output;
+
+    for (const auto& interval : mIntervals) {
+      TimeInterval reducedPrecision{interval.mStart.ToBase(USECS_PER_S),
+                                    interval.mEnd.ToBase(USECS_PER_S),
+                                    interval.mFuzz.ToBase(USECS_PER_S)};
+      output += reducedPrecision;
+    }
+    return output;
+  }
+
+  nsCString ToString() const {
+    nsCString dump;
+    for (const auto& interval : mIntervals) {
+      dump += nsPrintfCString("[%s],", interval.ToString().get());
+    }
+    return dump;
+  }
+
+  TimeIntervals() = default;
+};
+
+using TimeRange = Interval<double>;
+
+// A set of intervals, containing doubles that are seconds.
+class TimeRanges : public IntervalSet<double> {
+ public:
+  using BaseType = IntervalSet<double>;
+  using InnerType = double;
+  using nld = std::numeric_limits<double>;
+
+  // We can't use inherited constructors yet. So we have to duplicate all the
+  // constructors found in IntervalSet base class.
+  // all this could be later replaced with:
+  // using IntervalSet<TimeUnit>::IntervalSet;
+
+  // MOZ_IMPLICIT as we want to enable initialization in the form:
+  // TimeIntervals i = ... like we would do with IntervalSet<T> i = ...
+  MOZ_IMPLICIT TimeRanges(const BaseType& aOther) : BaseType(aOther) {}
+  MOZ_IMPLICIT TimeRanges(BaseType&& aOther) : BaseType(std::move(aOther)) {}
+  explicit TimeRanges(const BaseType::ElemType& aOther) : BaseType(aOther) {}
+  explicit TimeRanges(BaseType::ElemType&& aOther)
+      : BaseType(std::move(aOther)) {}
+
+  static TimeRanges Invalid() {
+    return TimeRanges(TimeRange(-nld::infinity(), nld::infinity()));
+  }
+  bool IsInvalid() const {
+    return Length() == 1 && Start(0) == -nld::infinity() &&
+           End(0) == nld::infinity();
+  }
+  // Convert from TimeUnit-based intervals to second-based TimeRanges.
+  explicit TimeRanges(const TimeIntervals& aIntervals) {
+    for (const auto& interval : aIntervals) {
+      Add(TimeRange(interval.mStart.ToSeconds(), interval.mEnd.ToSeconds()));
+    }
+  }
+
+  TimeRanges ToMicrosecondResolution() const;
+
+  TimeRanges() = default;
+};
+
+}  // namespace media
+}  // namespace mozilla
+
+#endif  // TIME_UNITS_H