Subtitle text aliasing - open subtitles VF

Anything and everything to do with DCP-o-matic.
Ryan
Posts: 7
Joined: Sat Feb 19, 2022 8:38 pm

Re: Subtitle text aliasing - open subtitles VF

Post by Ryan »

Thanks Carsten.

I am sure that 4K processing was enabled, but I'm not sure if the subtitles were being processed on the projector or server, I will try to find out and let you know. I'll also find some interop DCPs, do some comparisons and try to extract their fonts.

I've tried attaching a sample of the SRT file that I'm using here but it's not allowing me, it says it's an invalid extension, could I email it to you?

I haven't chosen a font as I am just using the default that DCP-o-matic is set to.

Regarding the screenshot, the feature is a 4K film with a 1.37 aspect ratio. The master file is a 3996x2160 ProRes4444 file, therefore it includes black bars.
Carsten
Posts: 2663
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Subtitle text aliasing - open subtitles VF

Post by Carsten »

Which font did you use that gave those results? We have a 4k Sony, and a 2k DLP projector. I could show a comparison.


I think not much work has been done to characterise timed text subtitling on DLPs. Up until very recently, all DLP cinema projectors contained exactly the same electronics and software to render the subtitles (the so called 'ICP'). At some point, server manufacturers added subtitle rendering to their server software, because at the time, projector-side subtitling was not available.

As a matter of fact - at least on 2k DLP projectors - you will usually hardly notice any visible pixel grid or aliasing with video content, but it typically becomes visible quickly when subtitles are shown. Server side subtitling in theory could use antialiasing, but, I never did a comparison. You would think that it's no problem on 4k systems. As a matter of fact, it is possible to run a 4k DCP on a 4k projector, but without 4k processing being enabled. I once created 4k checkerboard patterns to find systems that may be in that state - they would show a checkerboard in 4k, but just grey in 2k.

I'll send you my email by private forum message.
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