- From: Glenn Adams <glenn@skynav.com>
- Date: Fri, 15 Aug 2014 11:50:55 -0600
- To: Courtney Kennedy <ckennedy@apple.com>
- Cc: Nigel Megitt <nigel.megitt@bbc.co.uk>, Timed Text Working Group <public-tt@w3.org>
- Message-ID: <CACQ=j+d4hmsc5nnZroosy26N3ghrW1w6DNK=g0YRrcTvxpOYjg@mail.gmail.com>
I think we should keep it open and add support for ttp:mediaTimeOffset which could be negative. On Fri, Aug 15, 2014 at 11:30 AM, Courtney Kennedy <ckennedy@apple.com> wrote: > Hi Nigel, > > Ok, we can close this then. > > Best Regards, > Courtney > > Sent from my iPhone > > On Aug 15, 2014, at 9:03 AM, Nigel Megitt <nigel.megitt@bbc.co.uk> wrote: > > Hi Courtney, > > I agree it’s a real world situation, but I don’t understand why your > proposal is better than just putting the TTML file through a transformation > processor that adjusts all the times – hence my questions. > > At the point when you know what offset value to put into the document > you know what all the correct times should be, don’t you? > > If yes, you can already solve this problem with TTML. > If no, how do you assign the offset value? > > Am I missing something extra? > > Kind regards, > > Nigel > > > From: Courtney Kennedy <ckennedy@apple.com> > Date: Friday, 15 August 2014 16:31 > To: Nigel Megitt <nigel.megitt@bbc.co.uk> > Cc: Timed Text Working Group <public-tt@w3.org> > Subject: Re: ISSUE-335 (Negative times for offsets): In order to handle > offsets between start time in TTML docs and start time in video, allow > negative times to be used in fragment begin times. [TTML.next] > > HI Nigel, > > This is a real world situation that I have encountered with some > content. For whatever reason, the producers of the subtitles cannot use > the same start time as the producers of the video and audio. I think there > is a benefit to have all the information within the subtitles file rather > than having it in a sideband file which can get lost or separated from the > subtitles file. > > Best Regards, > Courtney > > On Aug 15, 2014, at 5:54 AM, Nigel Megitt <nigel.megitt@bbc.co.uk> wrote: > > Hi Courtney, > > I¹m puzzled by the implied workflow here: if the subtitle file and the > video have been created, at what point is the subtitle file modified to > include the new offset? And if someone or some system is making such an > edit why not simply make the times in the TTML correct against the video, > rather than adding an offset? > > I¹ve seen this issue arise before, when packaging TTML documents in ISO > BMFF (or some other wrapper). In that case the packaging is likely to > happen after production of all the media that would be wrapped so it seems > like the best way to capture any offset is using the facilities provided > by the wrapper rather than editing the content itself. Certainly ISO BMFF > appears to offer enough parameters/attributes to support that use case. > > I guess the key structural point is that there is a need to signal > equivalence of some time reference in the TTML with some other time > reference in a specific rendition of some related media. At the moment > this is expected to happen externally to the TTML document: why would we > bring it inside the document, given that no explicit link exists from > within a TTML 1 SE document to a related media object? > > Kind regards, > > Nigel > > > > On 14/08/2014 16:33, "Timed Text Working Group Issue Tracker" > <sysbot+tracker@w3.org> wrote: > > ISSUE-335 (Negative times for offsets): In order to handle offsets > between start time in TTML docs and start time in video, allow negative > times to be used in fragment begin times. [TTML.next] > > http://www.w3.org/AudioVideo/TT/tracker/issues/335 > > Raised by: Courtney Kennedy > On product: TTML.next > > Use case: > > Subtitles files may be created separately from video and audio for any > particular piece of content. Subtitles may be created in different > facilities and at different points in time than the original content. As > a result of this decoupling, sometimes the subtitles file will use a > different start time than the video and audio. > > Proposal: > > Time expressions in sub-elements are relative to the time expressions in > their parent elements, as described in section 10.2.4 of the TTML > specification. > > When subtitles have non-zero start times relative to the video they are > to be synchronized with, the parent div element can have an offset in the > begin attribute which, when applied to the times in the samples within > the div element, will produce time expressions that synchronize with > video. > > > The following example uses this offset to indicate that the titles are > using start time of 01:00:00:00, and require adjustment before their > values express the actual time they should appear in the video. > > > <div begin="-01:00:00:00"> > <p begin="01:00:05:00" end="01:00:10:00"> > This text should appear at 00:00:05:00 > </p> > </div> > > > > > > > > _____________________________________________ > Courtney Kennedy 408.974.3386, mobile: 408.771.8615 > Engineering Manager, Media Sharing > Apple, Inc. > > > > > >
Received on Friday, 15 August 2014 17:51:43 UTC