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RE: deprecating markerMode

From: John Birch <John.Birch@screensystems.tv>
Date: Mon, 14 Jul 2014 08:19:38 +0000
To: Nigel Megitt <nigel.megitt@bbc.co.uk>, TTWG <public-tt@w3.org>
Message-ID: <0981DC6F684DE44FBE8E2602C456E8AB016C0B70EE@SS-IP-EXMB-01.screensystems.tv>
Hi Nigel,

I don't recall any debate on the mailing lists.

When using SMPTE timecode *in the context of subtitling*, external context would dictate whether it is possible to calculate intervals between SMPTE timecode values.
i.e. regardless of any attribute in the TTML file, only the external context truly knows if the 'matching' AV asset has continuous timecode.

Even if a file is attributed as discontinuous markerMode, a processor might determine that the external AV asset is continuous (by examination of all frames for example) and thus determine intervals.

In general for me, the actual markerMode is a moot point, since I would generally expect a processor to act 'intelligently'... that is, treat the timecodes as markers (for in an out cues)... and perhaps only use timecode arithmetic if it was in possession of a 'bigger picture' of the timeline of the associated AV material.

But, this is only my perspective from a subtitling point of view...

If markerMode is deprecated, I would strongly suggest that all SMPTE timecodes are markers. I.e. the effective markerMode is then always 'discontinuous'.

Best regards,

John Birch | Strategic Partnerships Manager | Screen
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From: Nigel Megitt [mailto:nigel.megitt@bbc.co.uk]
Sent: 11 July 2014 15:03
Subject: deprecating markerMode


we noted in TTML1SE that ttp:markerMode may be deprecated, removing the possibility of using the value continuous (NB this is relevant only when timeBase = smpte). Can anyone remind me where the debate is on this? We don't seem to have an issue open for it and I don't recall discussing it.

Kind regards,



Nigel Megitt
Lead Technologist, BBC Technology, Distribution & Archives
Telephone: +44 (0)3030807996
Internal (Lync): 0807996
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Received on Monday, 14 July 2014 08:20:08 UTC

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