Two reels, one with subtitles and one without

[Seppia]

Hello

I just build a DCP with DCP-O-Matic containing two reels, that is actually a merge of two DCPs in one. The first DCP does not have caption, the second has closed caption (from a SRT imported in DCP-o-Matic).
Building goes fine, but when checking the DCP in (an older version of) EasyDCP Creator + 3.7.6, it prompts the following warning :

Code: Select all

Warning code 30035 from 2022-03-15T12:04:39+01:00:
Reel #1 does not contain Closed Caption.
Timed Text Tracks should be consistent throughout a composition. If reels are missing Timed Text Tracks that are present in others, this might cause undefined behavior during playback.

Has anyone ever encountered any playback issue in DCP theater players relate to this issue ? Can I safely ignore it ? Or should I rebuild my DCP with only one reel ?
If it's actually problematic, then I suggest DCP-O-Matic should add automatically an empty subtitle track to every reel when building a DCP containing (at least) one reel with closed caption.

[carl]

What version of DCP-o-matic are you using?

[Seppia]

What version of DCP-o-matic are you using?

It was in the 2.14, just before I saw, coming here to post, that the 2.16 had been released
Still not on brew.sh, though :'(

[mdudzik]

Dear Seppia, you can just ignore it - I've never encountered a single issue with any DCP not having subtitles for all reels - and I've seen many of them with logos added at head etc.

[Seppia]

Dear Seppia, you can just ignore it - I've never encountered a single issue with any DCP not having subtitles for all reels - and I've seen many of them with logos added at head etc.

Thanks, as you guessed that's exactly the case : the classic 6 seconds animated logo to be inserted at the beginning of the DCP, when you already have encoded the whole JPEG2000 .MXF of the 90 minutes feature. Blessed be the reels and the rewrap

In the meantime I realized that my subtitles were not Closed Caption (= for accessibility device purpose) but the common Open Caption (just another language translation). So I re-defined them as OCAP and not CCAP in DCP-O-Matic.

Also I updated to the 2.16 version of DCP-O-Matic, and when I rebuilded my DCP I noticed that it added an empty Open Caption track on the first reel as well (maybe it was already the case in 2.14 ?).

Now I have a DCP consisting of two reels, both with Open Captions tracks (one empty automatically added by DCP-O-Matic, and the second one are the real subtitles from my .SRT file).
I just have to check it to be sure I haven't accidentally moved the subtitles, but on the paper it seems fine (and EasyDCP Creator didn't complain this time)

[Carsten]

The necessity to have subtitles in all reels if just a single reels needs one, is a clear requirement BECAUSE some prominent servers have trouble with DCPs not following this requirement. Even if someone did not have issues before, it is recommended to follow this rule.

'Dummy sub Files
Background: SMPTE RDD52 indicates that if a composition contains ANY reel having timed text that ALL reels should have a timed text element. There is a need to define a “blank” subtitle/timed text track to meet this requirement. This is needed to “work around” a problem in a number of deployed servers that will not properly work (timed text either not working or appearing out of time sync) without these files. It is a known SMPTE-DCP issue that mastering companies have been addressing for years. This just makes it formal and a uniform way to build a work-around.
SMPTE ST 429-2, section 9.8 Timed Text, states the following:
“Once a timed text asset appears in one Reel, the established track shall be assumed to exist for the entire Composition, even if related timed text Asset elements are not present in all Reels.”
To mitigate such behavior, RDD 52, section 8.3.1 states the following:
If a MainSubtitle timed text track is present on any reel, a MainSubtitle timed text track shall be present on all reels. If (1) or more ClosedCaption timed text track(s) are present on any reel, the same number of ClosedCaption timed text tracks shall be present on all reels.'

https://ieeexplore.ieee.org/stamp/stamp ... er=9161348

https://isdcf.com/papers/ISDCF-Doc-16_E ... _draft.pdf


Current versions of DCP-o-matic will make sure that dummy caption reels are created where necessary.
Many people create DCPs with DCP-o-matic that contain only a single reel anyway, so, that requirement is easy to comply with.

[Seppia]

Thanks a lot Carsten for your detailed clarification about this dummy/empty subtitle track requirement rule, when using multiple reels