Transcoding from existing DCP

[pauls]

I've created a DCP in Resolve Studio (Mac), and then opened it in DCP-o-matic in order to edit the metadata, put in the correct markers etc., with the intention of creating version with subtitles. The problem is that when I try to make a new OV DCP using the existing DCP, it insists on transcoding, at a rate of ~8 or 9 frames per second. At this speed I'm assuming it's not passing through the existing video, but actually doing a transcode, however I have changed none of the details about the DCP other than some metadata and markers. Could those be triggering a transcode?

[IoannisSyrogiannis]

You mean to create a VF only with the subtitles?
Could it be that the DCPs are one IOP and the other SMPTE?
Could it be that you didn't tell DCP-o-matic to keep video and audio and make a VF?
Could it be that one DCP is in reels and the other is not?
Could it be that you export Flat, when the other was Scope, or the other way around?
Could it be that the Re-encode JPEG2000 data from input box is checked?
Could it be that you go by intuition and you missed a step?

What you call details could be a number of things and we people here don't know what is it that you mean exactly.

[carl]

If you right-click on the DCP in the DCP-o-matic list (after you add it to the project) and choose "Set project DCP settings from this DCP" that should increase your chances of not needing a transcode.

[pauls]

Yes I set the project settings from the original DCP. And I have tried it from a few different DCPs (all made via Resolve)
Here are the exact steps I took:

New Project
Select path, project name
Add DCP
Select existing DCP
Open
Right Click, set project DCP settings from this DCP
Click on DCP tab
Click on Markers…
Set:
First frame of title credits
Last frame of title credits
First frame of end credits
Last frame of end credits
First frame of moving credits
Last frame of moving credits
Click on Audio tab
Click on language
Click on Edit
Choose English en
Save project
Click Jobs > Make DCP
Ignore Hints about using 8 channels instead of 6
Click Make DCP

And this leads to the project being transcoded. Have I missed a step here? Or does one of these alterations necessitate a transcode?

[carl]

I think that should be fine. The messages about what's going on are not very detailed, unfortunately - it says "transcoding" when it really is transcoding, but also when it just copying data.

Is your CPU heavily used while this 8/9fps transcode is happening?

Granted, I'd expect it to be faster, but maybe there's some other bottleneck, and it really is copying the data (but quite slowly).

[carl]

You could enable the "debug: encode" checkbox in the advanced preferences. Then in the log file you should see things like "Frame @ 1234 J2K" if that frame's data was copied, or "Frame @ 1234 ENCODE" if it was re-encoded.

[carl]

One other thought is to check what resolution your original DCP - is it in a 1998x1080 or 2048x858 frame?

[pauls]

I think you're right - it's not actually transcoding. I turned on the encode debugging and checked the log and it looks like it's just copying it across. I'm using SSDs connected by USB-C, so I'm not sure where the bottleneck is, but I'll work on figuring that out. Good to know I'm not doing something wrong to trigger a transcode.
Thanks for your help!

[Carsten]

You could try a short piece on the internal system SSD to see wether it makes a difference.