Film-Tech Forum ARCHIVE: Subtitles cutting off

This is topic Subtitles cutting off in forum Digital Cinema Forum at Film-Tech Forum ARCHIVE.

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Posted by Richard May (Member # 2627) on 02-17-2018, 10:52 AM:

Bottom half of subtitles are being cut off. Movie is 4K scope. When I play the movie in 2K scope, subs are fine. It's not the cropping. I removed any just to see. All the macro settings are exactly the same for 2K and 4K scope except for the source file obviously. Projector is a Christie CP4220. Server is GDC SX-3000. When I put up the safe image test pattern, the subs that are cut off are down in the red area, outside the safe image area.

Posted by Stephan Shelley (Member # 8587) on 02-17-2018, 11:25 AM:

Are you sure it is a 4K DCP? It is a common problem to have subtitles of a 2K DCP in the wrong place when playing back in a 4K macro.

Posted by Richard May (Member # 2627) on 02-17-2018, 12:20 PM:

I've seen that too. It says 4K on the DCP and the information tab on the GDC has it as 4096 X 1716.

Posted by Dave Macaulay (Member # 813) on 02-17-2018, 12:35 PM:

haven't tried a 4K Christie but I believe Barco 4K needs a 4K scope PCF to position 4K scope DCP subtitles correctly.

Posted by Richard May (Member # 2627) on 02-17-2018, 12:54 PM:

Tried it. Still no good. I'm just going to run it in 2K for now. BTW, while in 4k macro, all trailer's subtitles played fine. It was only the feature that the subs are cut off.

Posted by Stephan Shelley (Member # 8587) on 02-17-2018, 02:21 PM:

What PCF are you using or if not using a PCF what screen file.

Posted by Richard May (Member # 2627) on 02-17-2018, 02:36 PM:

I'm using a 4096 X 1716 2.39 Scope screen file but I also tried switching to a DC4K_DCDM_XYZ_239 PCF file. There was no change.

Posted by Stephan Shelley (Member # 8587) on 02-17-2018, 02:53 PM:

You could try auto square pixels screen file or the auto PCF if there is one.

Posted by Carsten Kurz (Member # 5396) on 02-17-2018, 02:59 PM:

Is this an interop DCP? You may transfer one of the subtitle folders xml files to a computer and check the positioning metadata. That should tell you wether it's equipment, or DCP related. If you say that the titles are in the red area, that area SHOULD still contain visible image content. So, if the titles are cut off there, it must be the cropping or the masking (or the lens setting)?! Yes, maybe the subtitle positioning for this feature may be a bit sharp. I assume that where the subtitles are cut off, you can see no image content as well?

- Carsten

Posted by Richard May (Member # 2627) on 02-17-2018, 03:47 PM:

Correct, no image at all where the subs are cut off. Projector masking (cropping) is off.

Posted by Carsten Kurz (Member # 5396) on 02-17-2018, 04:26 PM:

If cropping is off, how can there be red in the test chart where the subs are cut off?

- Carsten

Posted by Richard May (Member # 2627) on 02-17-2018, 04:38 PM:

The subs are cut off right where the safe image ends outside of the scope area on the pattern.

Posted by Carsten Kurz (Member # 5396) on 02-17-2018, 06:33 PM:

Don't know that specific test pattern - usually, the 'safe area' is well within the visible image area. If that red border in your test clip is actually outside of the 2048*858/4096*1716 scope frame, than they are indeed positioned too low, and that red area is an 'invisible area'.

- Carsten

Posted by Richard May (Member # 2627) on 02-17-2018, 06:54 PM:

Correct. The red area should have no content. Too bad I don't have another 4K movie with subs. I will just run it in 2K for now.

Posted by Carsten Kurz (Member # 5396) on 02-17-2018, 07:32 PM:

The SX-3000 should have it's own server-side subtitle engine. Do you know wether the SX-3000, or the Christie is configured to render the subtitles?

- Carsten

Posted by Richard May (Member # 2627) on 02-17-2018, 07:34 PM:

I had already tried looking for it but couldn't find it in either.

Posted by Stephan Shelley (Member # 8587) on 02-17-2018, 07:38 PM:

Should be in the configuration menu.

Posted by Richard May (Member # 2627) on 02-17-2018, 08:14 PM:

Sorry. I misread the post. I will try enabling the GDC subtitle engine. Projector is rendering now.

Posted by Carsten Kurz (Member # 5396) on 02-17-2018, 08:23 PM:

Again, you could try to transfer one of the subtitle files to a PC and have a look (usually, double-clicking it will open it for viewing in a browser). If it's an Interop DCP, the subtitled DCP/CPL should be accompanied by a couple of folders, each one containing a TTF font file, and a subtitle reel XML file.

The vertical alignment reference can be changed from top, center, to bottom. The vertical position for the text baseline is given in percent of frame height from reference. That is, if vertical reference is from top, running text exactly on the lower border is done by aligning it '100% from top'. The same could be done by '0% from bottom'. Note that putting text there will cut of descenders even if no cropping is active, because the text position is referenced to the text baseline, while the descenders stretch out below the baseline.

So, if you have a chance to look into one of these files, check these values.

In order for the the projector to position these subs properly, it needs to know about the active area configured in the Macro - otherwise it would reference e.g. 90% from the top of a flat active area for a scope movie. That's why it is important to have the proper PCF selected.

A typical commercial scope DCP ('Moonlight') e.g. had one liners at 6% above bottom (94% from top), and the top line of two liners at 12% from bottom (88% from top).

e.g.

<Text HPosition="0" VAlign="bottom" VPosition="12">Hey, Mom.</Text>
<Text HPosition="0" VAlign="bottom" VPosition="6">- You can't stay here today.</Text>

- Carsten

Posted by Richard May (Member # 2627) on 02-17-2018, 08:27 PM:

I enabled the GDC subtitle engine and the subs are all correct now. Not sure why but it works. Thanks guys.

Posted by Carsten Kurz (Member # 5396) on 02-17-2018, 08:32 PM:

Don't know the exact reason why the projector engine is wrong here - but when the GDC renders subs, it necessarily knows exactly the image dimension, a scope DCP will render to 2048/858 or 4096/1716. The subtitle engine then places the text according to the rules I explained above and renders it into the individual frames. The projector PCF is then irrelevant for the sub position reference, as the text has been burnt into the image. Only excessive vertical cropping can then cut off the bottom part of the image and text rendering.

- Carsten