Re: Initial value of ttp:markerMode

as TTML is defined, smpte time base is always marker based, whether the
markers are continuous or not;

we had defined 'continuous' irrespective of the value of the first marker,
and irrespective of use of drop frame, since neither of these result in
uncomputable discontinuities that prevent calculating duration; that is,
duration is computable with drop frame and arbitrary start time if you know
the drop frame mode and have read the first marker;

on the other hand, if post production edits result in the insertion or
deletion of material that introduces other types of non-linearity, e.g., a
jump forward or backward of time codes, or a different rate of time codes
with respect to media time (PTS), then those edits would constitute
discontinuous mode;

On Thu, May 24, 2012 at 7:47 AM, Michael A Dolan <mdolan@newtbt.com> wrote:

> SMPTE timecode is often discontinuous due to post production edits, and
> (in the US for non-integer framerates) always dropframe mode, and common
> practice is to start the first frame of the media at 1 hour (not zero),
> thus making presentation time undefined.  So, SMPTE timecode is nearly
> always marker mode.  The special case is actually when it is usable as a
> non-marker timebase.****
>
> ** **
>
> Regards,****
>
> ** **
>
>                 Mike****
>
> ** **
>
> *From:* Glenn Adams [mailto:glenn@skynav.com]
> *Sent:* Wednesday, May 23, 2012 11:45 PM
> *To:* Andreas Tai
> *Cc:* public-tt@w3.org
> *Subject:* Re: Initial value of ttp:markerMode****
>
> ** **
>
> I have never thought that markerMode was intended to primarily express
> discontinuous markers. When we created this property, the discontinuous
> mode was thought to be an exception rather than the default. So without
> considerable further discussion, I would hesitate to accept this proposal.
> ****
>
> On Thu, May 24, 2012 at 12:27 AM, Andreas Tai <tai@irt.de> wrote:****
>
> I would like to propose to change the initial value of markerMode from
> contineous to discontineous. As seen in discussions the intended meaning of
> markermode aligns more with the expressed meaning of markermode
> "discontineous".
>
> What do you think?
>
> Best regards,
>
> Andreas
>
> --
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>
> ** **
>