The AudioEndTime()[0] will return a time that is over the end of the track after the media is looped seamlessly. Looping or not, it should return the correct end time. [0] https://searchfox.org/mozilla-central/rev/9f3bd430c2b132c86c46126a0548661de876799a/dom/media/MediaDecoderStateMachine.cpp#3625

Comment on attachment 8941752 [details] Bug 1421505 - Return the correct duration while seamless looping is on; https://reviewboard.mozilla.org/r/211974/#review217732 ::: dom/media/MediaDecoderStateMachine.cpp:3691 (Diff revision 1) > > TimeUnit > MediaDecoderStateMachine::AudioEndTime() const > { > MOZ_ASSERT(OnTaskQueue()); > + if (mReader->GetDuration().IsValid()) { https://searchfox.org/mozilla-central/rev/88439dc6c5b02e167032374071cdc697a056efa1/dom/media/MediaDecoderStateMachine.h#571-574 AudioEndTime() is not the duration. It is the end time of the last audio frame that's been pushed onto the media sink which changes constantly as we push more frames to the audio sink.

This should be fixed in MediaSink, but MediaSink doesn't know the seamless-looping is on or not. This will be fixed when we figure out how to pass the seamless-looping info to MediaSink.