[Bug 19676] timestampOffset accuracy

https://www.w3.org/Bugs/Public/show_bug.cgi?id=19676

--- Comment #18 from Aaron Colwell <acolwell@chromium.org> ---
(In reply to comment #17)
> Thanks. Couple of follow-up issues:
> 
> > Let remove window timestamp equal overlapped frame presentation
> > timestamp plus 1 microsecond.
> 
> This seems to apply only when there is overlap. If so, what about if the
> splice is supposed to happen at the end of the existing frame buffer, i.e.
> the end of the last frame of the existing frame buffer corresponds to the
> start of the first frame of the added segment?

Yes. The frame will be inserted at the specified timestamp if there isn't
overlap.

> 
> > Update presentation timestamp and decode timestamp to the nearest audio
> > sample timestamp based on sample rate of the audio in overlapped frame.
> 
> Don't we need to adjust timestampOffset so that the following frames will
> align as well?

No. The point of this mechanism is not to modify timestampOffset. It is to make
sure that timestamps that are slightly off can properly trigger removal of
existing frames in the buffer. The UA is not in the position to override the
web applications intent. It is up to the web application to make sure that
timestampOffset is as accurately set as possible.

> 
> >  then remove overlapped frame and any coded frames that depend on it from track buffer.
> 
> Same here, don't we need to adjust timestampOffset so that the presentation
> time of following frames reflect the small offset as well?

No.

> 
> >  There is no need for a rounding tolerance for audio.
> 
> What about if the splice is designed with no overlap, and the coded audio
> frames are supposed to butt?

If there is no overlap then there isn't a problem. The specified timestamp will
be used and if there is a slight gap then silence will be inserted. The sample
rates aren't very high so if the application has trouble accurately specifying
the start of the frame then it can expect problems.

> 
> > that overlap presentation timestamp plus the splice duration of 5 milliseconds.
> 
> Larger than or equal?

I'll add text to clarify this refers to all coded frames that have presentation
timestamps > _presentation_timestamp_ and < _presentation_timestamp_ + 5
microseconds.

-- 
You are receiving this mail because:
You are the QA Contact for the bug.

Received on Monday, 25 March 2013 17:00:36 UTC