In void nsOggDecodeStateMachine::Seek(float aTime) we assert: mSeekTime = aTime + mPlaybackStartTime; float duration = static_cast<float>(mDuration) / 1000.0; NS_ASSERTION(mSeekTime >= 0 && mSeekTime <= duration, "Can only seek in range [0,duration]"); That's wrong. mSeekTime is in range [mPlaybackStartTime, mPlaybackStartTime+duration], so the assertion should be: NS_ASSERTION(mSeekTime >= mPlaybackStartTime && mSeekTime <= (mPlaybackStartTime + duration), "Can only seek in range [start,end]"); We should probably assert that the passed in time (aTime) is in range [0,duration], at least until we update the start time to match the current spec, which exposes HTMLMediaElement.currentTime to be in the range [HTMLMediaElement.startTime, startTime+duration_of_all_concatenated_segments] rather than [0,duration] as we currently implement. See: http://www.whatwg.org/specs/web-apps/current-work/multipage/video.html#dom-media-currenttime

Ok, the new Ogg decoder backend implemented the assertion as my comment 1, but we're still not matching the spec. We still start playback at time 0, and end it at time |duration|. Playback should start at time HTMLMediaElement.startTime, and finish at |startTime+duration|.

(In reply to comment #1) > Playback should start at time > HTMLMediaElement.startTime, and finish at |startTime+duration|. This is bug 498253.