--- a/dom/media/MediaDecoderStateMachine.cpp
+++ b/dom/media/MediaDecoderStateMachine.cpp
@@ -810,23 +810,22 @@ private:
     // don't run out of audio. This is unnecessary for async readers,
     // since they decode audio and video on different threads so they
     // are unlikely to run out of decoded audio.
     if (Reader()->IsAsync()) {
       return;
     }
 
     TimeDuration decodeTime = TimeStamp::Now() - aDecodeStart;
-    int64_t adjustedTime = THRESHOLD_FACTOR * DurationToUsecs(decodeTime);
-    if (adjustedTime > mMaster->mLowAudioThreshold.ToMicroseconds()
+    auto adjusted = TimeUnit::FromTimeDuration(decodeTime * THRESHOLD_FACTOR);
+    if (adjusted > mMaster->mLowAudioThreshold
         && !mMaster->HasLowBufferedData())
     {
       mMaster->mLowAudioThreshold = std::min(
-        TimeUnit::FromMicroseconds(adjustedTime),
-        mMaster->mAmpleAudioThreshold);
+        adjusted, mMaster->mAmpleAudioThreshold);
 
       mMaster->mAmpleAudioThreshold = std::max(
         mMaster->mLowAudioThreshold * THRESHOLD_FACTOR,
         mMaster->mAmpleAudioThreshold);
 
       SLOG("Slow video decode, set "
            "mLowAudioThreshold=%" PRId64
            " mAmpleAudioThreshold=%" PRId64,