Re: Initial value of ttp:markerMode

I agree that from a formal perspective this creates a backwards 
incompatibility. I based the proposal on the fact that until now in 
operation timebase "smpte" is rarely or not used. Therefore I thought 
that the "perceptual benefit" will balance the backwards incompatibility.


In any case, from the perspective of the EBU TTML Subset it has to be 
very clear what it is meant with the different markermodes. A broad 
agreement on this would be good and very helpful.


Glenn said

"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;"


and Mike noted "SMPTE timecode is often discontinuous".


My question is: Was the intention of markerMode "discontinuous" to 
indicate discontinuous time coordinates/timecodes? If in a TTML document 
sets the markermode to "discontinuous", does this imply that the 
timecodes are discontinuous (e.g. because of timecode jumps)?


I know what the spec says about this but from my view this leaves to 
much room for interpretation.

Thanks and best regards,


Andreas


Am 24.05.2012 16:13, schrieb Michael A Dolan:
>
> Right.  To be clear, I wasn’t taking a position on the proposal; just 
> noting the “common” properties of SMPTE timecode.
>
> To the proposal, it creates a backwards incompatibility with only a 
> perceptual benefit.  I think this would be better addressed with 
> explanatory text in the Recommendation.
>
> Regards,
>
>                 Mike
>
> *From:*Glenn Adams [mailto:glenn@skynav.com]
> *Sent:* Thursday, May 24, 2012 6:55 AM
> *To:* Michael A Dolan
> *Cc:* public-tt@w3.org
> *Subject:* 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 
> <mailto: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 <mailto:glenn@skynav.com>]
> *Sent:* Wednesday, May 23, 2012 11:45 PM
> *To:* Andreas Tai
> *Cc:* public-tt@w3.org <mailto: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 
> <mailto: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
>
> -- 
> ------------------------------------------------
> Andreas Tai
> Production Systems Television IRT - Institut fuer Rundfunktechnik GmbH
> R&D Institute of ARD, ZDF, DRadio, ORF and SRG/SSR
> Floriansmuehlstrasse 60, D-80939 Munich, Germany
>
> Phone: +49 89 32399-389 <tel:%2B49%2089%2032399-389> | Fax: +49 89 
> 32399-200 <tel:%2B49%2089%2032399-200>
> http: www.irt.de <http://www.irt.de> | Email: tai@irt.de 
> <mailto:tai@irt.de>
> ------------------------------------------------
>
> registration court&   managing director:
> Munich Commercial, RegNo. B 5191
> Dr. Klaus Illgner-Fehns
> ------------------------------------------------
>
>


-- 
------------------------------------------------
Andreas Tai
Production Systems Television IRT - Institut fuer Rundfunktechnik GmbH
R&D Institute of ARD, ZDF, DRadio, ORF and SRG/SSR
Floriansmuehlstrasse 60, D-80939 Munich, Germany

Phone: +49 89 32399-389 | Fax: +49 89 32399-200
http: www.irt.de | Email: tai@irt.de
------------------------------------------------

registration court&   managing director:
Munich Commercial, RegNo. B 5191
Dr. Klaus Illgner-Fehns
------------------------------------------------