Audio delay on 23.976 source video

[chrusli]

Hi awesome DCP-o-matic people

I'm trying to create a DCP from a 4k MKV. I have read that DCP-o-matic does stretch the audio in order to be in sync when creating a 24 fps version (how great is that ) from a 23.976 fps source. It doesn't seem to work for me. The audio is off by maybe a few seconds at the end of the movie.

Codec infos of the MKV (which I can share if needed)

bttf_videocodecinfos.jpg

DCP Video settings

bttf_videosettings.jpg

bttf_dcpvideosettings.jpg

What am I doing wrong?

Thank you!

Best regards
Stephan

[chrusli]

I forgot to add the audio settings and couldn't add them on the original post, so here they are

bttf_dcpaudio.jpg

bttf_audio.jpg

[Carsten]

Which version of DCP-o-matic are you using? It looks like an older version, though.

Per design - if you add a 23.97 fps combined video/audio file (same for 25fps, btw), and set the DCP property to 24fps, DCP-o-matic will automatically adjust video frame rate AND audio sample to match. BUT - for audio, DCP-o-matic will usually tell you that under audio properties. Your screenshots do not indicate this per-default processing. But maybe you overcompensated the frame rate difference by setting a different video frame rate reference under 'timing'?

See my screenshots.

I suggest you remove the content from the project, and add it again, then don't touch the frame rate reference setting under timing.

- Carsten

[IoannisSyrogiannis]

What I would suggest, is to use MKVToolNix (GUI) to export the video with only the audio you want to use.
Then, make the DCP.
[...]

Edit (irrelevant):
I see some 4.000 cd/m2 in luminosity.
Is this HDR?
Did you check the video result?

[chrusli]

Thank you, Carsten, for your help. You really have a spectacular service!

You are right, I had an ancient version (2.14.xx). That is a bit strange, as I checked for updates, and it didn't indicate anything, and I have the box checked to check for updates upon start. I downloaded and installed the latest version now. I'm already happy with the latest release, since the playback of 4k is now running smooth!

I'm recreating the movie now and will tell you after it's done how it went. But I seem to remember having changed the frame rate from 23.976 to 24 at one point. Funnily, I don't see this option anymore.

bttf_timing.jpg

[chrusli]

@IoannisSyrogiannis Thank you for your hints.

What I would suggest, is to use MKVToolNix (GUI) to export the video with only the audio you want to use.
Then, make the DCP.
[...]

I will do that next time. What is the reason to do that? Does it take up space in the DCP as the other audio tracks are included as well?

I see some 4.000 cd/m2 in luminosity.
Is this HDR?
Did you check the video result?

It's Dolby Vision HDR10+. I haven't yet seen the result DCP on my computer and won't be able to watch it in theater until the beginning of August. Should I be worried .

Best regards
Stephan

[Carsten]

In the current version, the frame rate reference setting now went into content properties (right click on the content). It's a bit safer there


You are about to create a DCP from an UHD source. While DCP-o-matic properly recognises the color space, it currently to my knowledge does not perform a proper REC.2020/PQ->X'Y'Z' transformation for digital cinema. The color at first will look 'okay', but often washed out (depending on the content), and highlights being muted. I guess you would get a better result from a standard Bluray, even if in 1920p resolution. My own tests so far have been disappointing. Yes, you do see an image in preview, but it lacks a lot of snap compared to the remastered standard Bluray.

Maybe we can solve that issue soon. I heard that VLC can now display HDR material transformed to rec.709 or RGB, so, the necessary framework should be there. How they deal with the very different target luminance range, I have no idea, but, as in common HDR capable TVs, they also need to do some luminance adoption with it.

Maybe there are third party processors that will transform the source color-space to a linear or traditionally gamma coded REC.2020 color space. That would make it easier for DCP-o-matic to work with it.

I notice this is a classic title that underwent a remastering towards UHD - you will most certainly be able to buy a Bluray that has been created from the same remastering process. That will probably give better results than the UHD. Maybe you already have that Bluray within the same box as the UHD.

[chrusli]

In the current version, the frame rate reference setting now went into content properties (right click on the content). It's a bit safer there

That will probably save you some questions like mine .

Thank you for the warning about using the UHD source. I'll get the Bluray version then!

[Carsten]

If you have the time, create both version as DCP and check them. I myself have a Bluray and UHD MKV of another classic title, and while I was able to check the colors of the UHD version came out insufficient, I did not yet create both versions as a DCP for a direct on screen comparison. It is certainly interesting to watch both versions for a comparison.