DCP to DCP without changes

[MartinL]

Good morning,

I have a question and I'm not even certain if DCP-o-Matic really does what I'm thinking it's doing right now.
So either I need some suggestions or a general clarification if I got something wrong.

I'm currently trying to convert a 3D DCP into a 2D DCP. Since DCP-o-Matic is one of the only programs
that can work with 3D DCPs I thought I could just open the 3D DCP in a new project and export it
back again as 2D DCP.

This worked but when I analyzed the picture quality in Resolve late I noticed that the Gamma settings were off.
Typically a DCP uses a Gamma of 2.6 while other formats use 2.2 or 2.4. When I edit DCPs I often notice that
2.2 is too dark and I change it to 2.6. But for the DCP that was created in DCP-o-Matic 2.2 was a bright as
2.6 would usually be and changing it manually to 2.6 in Resolve created a much too bright picture.

So I'm sure in this conversion from 3D to 2D DCP-o-Matic applied some conversion settings that are usually required
when you convert from say ProRes to DCP. If I want to keep the color as it is, so XYZ or X'Y'Z', the bitrate as it is with 12-bit
and especially the gamma as it is, so if I only want to transcode the footage from 3D to 2D, is there a setting I could
chose in my project to make sure DCP-o-Matic is not adding or changing anything during the export?

Thank you for any suggestions

[carl]

That's strange. I just did a quick test of 3D -> 2D and the JPEG2000 data in the output is identical to that in the left eye of the input.

Can you attach the metadata.xml of the project you used to make the conversion? Or email it to carl@dcpomatic.com ?

[MartinL]

Thank you for the fast reply:

I will have to re-do it then since I already deleted the converted file.

Which of the programs did you use for the conversion, the standard DCP-O-Matic or one of the other tools like the Batch Converter?

[carl]

I wrote a test in C++, but it should work the same in either the main DoM or the batch converter.

[Carsten]

How long did the export take? If the gamma is changed, DCP-o-matic needs to recompress the images, wich will take long. This is not necessary for a straight 3D->2D conversion, where DCP-o-matic will just pass through the J2K images for one eye. That lossless conversion (well, lossless as far as only one eye is the intention) should go pretty fast, basically, just a file writing process.


- Carsten

[auta]

Hey!

Why do I create a new one DCP from 2 tlr DCP, mxf recoded?
I uncheck transcode jpeg2000
Content split by video

I'm using version 2.16.36

[carl]

Perhaps you can provide the metadata.xml from your project.

[auta]

metadata.xml in attache

[carl]

When you say the "MXF is recoded", how do you mean? DCP-o-matic will re-write the MXF file, but re-use the JPEG2000 data bit-for-bit from the old one. Are you expecting it to re-use exactly the same MXF?

[auta]

Yes, i expecting to re-use exactly the same MXF.

I'm tested in Clipster system, and he is not re-write MXF, he is copy and save same hash.

See in screenshots