Re: Initial value of ttp:markerMode

On Fri, May 25, 2012 at 6:07 AM, Andreas Tai <tai@irt.de> wrote:

> My question is: Was the intention of markerMode "discontinuous" to
> indicate discontinuous time coordinates/timecodes?
>

yes, but i'm curious why you would ask this question? the following
language, specifically the phrase "time coordinates" is pretty clear to me,
i.e., ("time coordinates" = "SMPTE time code markers"; how would you like
to see it improved?

"The ttp:markerMode attribute is used to specify constraints on the
interpretation and use of time expressions that correspond with [SMPTE
12M]<http://www.w3.org/TR/ttaf1-dfxp/#smpte12m> time
coordinates when operating with time base of smpte as defined by *6.2.11
ttp:timeBase*<http://www.w3.org/TR/ttaf1-dfxp/#parameter-attribute-timeBase>
."

"if discontinuous, then any assumption must not be made regarding linearity
or monotonicity of time coordinates"


> If in a TTML document sets the markermode to "discontinuous", does this
> imply that the timecodes are discontinuous (e.g. because of timecode jumps)?
>

not exactly; it is certainly possible to specify discontinuous when there
are no non-linearities and time coordinates are monotonic; the real purpose
of specifying discontinuous is to indicate to the presentation (or
transformation) processor that no assumptions can be made about
linearity/monotonicity of time coordinates; furthermore, if discontinuous
is specified, then use of @dur attribute or use of offset-time time
expressions would be invalid;

perhaps this latter point is not so clear, however, and needs to be made
more explicit (and tests added to test suite);