Duration and entry point in CPL

Anything and everything to do with DCP-o-matic.
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jdent02
Posts: 35
Joined: Wed Nov 04, 2020 10:32 pm

Duration and entry point in CPL

Post by jdent02 »

Had a question on why DOM does something the way it does....

On the timing tab there's an option for trimming the start or end of a media piece. When you encode it always removes that trimmed content from the video file(s), which makes sense in the case of multiple media files being joined into one reel. But when each media file is set as it's own separate reel, why isn't that trim reflected as entry point and duration modifiers in the CPL instead, like EasyDCP does?

It doesn't really affect how I use DOM at all but one of the DCI requirements I've seen before is that to be fully compliant, reel media needs to have leader and trailer pops on them, even in the DCP. These pops are then skipped over with entry point modifiers during playback.

Like I said, just curious.
carl
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Re: Duration and entry point in CPL

Post by carl »

It's a good question, and something which has been asked for before in the context of this leader/trailer pops requirement.

In a nutshell, it's hard to do with the code as it is. There is a fairly deeply-held assumption that we don't encode or write the trimmed parts of any content.

In particular, there's this awkward case where you might have two pieces of content next to each other, with the first having a trimmed end and the second having a trimmed start. Then, you have to transcode the trimmed end of A and the trimmed start of B, write them to disk, but not show them in the preview.

It's possible, but just not easy, and fairly rarely requested, so this feature hasn't made it to the top of the list yet.

That being said, I was in touch with someone who had a lot of difficulty getting a DCP through QC because they insisted on these leader/trailer pops, so it's something we'll have to add eventually.

There's this bug to track this feature.
Carsten
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Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Duration and entry point in CPL

Post by Carsten »

BTW - we DID have this feature in very early versions of DCP-o-matic / DVD-o-matic. We could even select between hard and soft trimming then. But - as Carl says, the code to deal with content has changed completely with DCP-o-matic v.2, and it not as easy as just re-enabling that part.

There is no requirement in any SMPTE standard or in RDD52 to include leaders/tails/pops, so, a DCP without them is 100% okay. Just that some companies want them for sync QC. Wondering wether we could actually leave away the entry point option from DCP-o-matic, but add an option to simply create a sync-pop to every reel during conversion/encoding, so that they are happy. That is probably a lot easier to do currently.


- Carsten
jdent02
Posts: 35
Joined: Wed Nov 04, 2020 10:32 pm

Re: Duration and entry point in CPL

Post by jdent02 »

I suppose it wouldn't be that difficult to modify the CPL, although I suppose that would invalidate the hash in the assetmap.
Carsten
Posts: 2266
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Duration and entry point in CPL

Post by Carsten »

It would certainly be possible to do a brute force CPL modification, then load the invalid DCP into a forgiving application (DCP-o-matic), then just rewrap. DCP-o-matic can deal with pre-existing non-zero entry points in DCPs, it just can not create them by itself based on raw footage.
igit
Posts: 15
Joined: Wed Sep 18, 2019 12:35 pm

Re: Duration and entry point in CPL

Post by igit »

It's not like it's a holdover from the film when the leaderboards were needed, but in reality I very rarely see DCP where they are.
Also, more and more often DCPs are made without splitting into reels.
the only thing is full-fledged work with reels - for example, as in Transkoder or Clipster - I can use reels to do soft trimming and insert a replacement for the main title of the movie, while the main video will not be modified.
This is good, because such a DCP will actually contain the original Main Title and the localized one.
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