Perhaps someone can clarify for me as to when it, if at all, it would be justified to use or create a source file that deviates from the standard square pixel flat/scope/HD/custom or has an specified aspect ratio that differs from the signal aspect ratio and grid specified?
Our 2k CP2220 has a ton of differing grid size source files populated, either from factory or from past users. Most of which seem completely irrelevant when running 2K F/S/Custom DCPs or 1080p alt content.
Separately, the source file setup has that tickbox for "Letterboxed", and lets you specify an intended aspect ratio (that may differ from the pixel grid that is entered), but the naming of that feature seems problematic cause it seems to have the capacity be relevant to pillar-boxing too? I assume if you don't want any pixel stretching or squishing you always set the source aspect to match the signal pixel grid you entered, unless you are doing some offset perhaps.
Is my understanding correct that when the grid ratio (after any offsets) and the "specified" source aspect ratios match, that is what is considered "square pixels". And if they are mis-matched in any way effectively you are manipulating the pixels to non-square (an expression, but that is the terminology in use).
Is the source aspect ratio setting (flat/scope/or manually entered) intended as a channel tool to allow you to stretch one source into a different aspect ratio than it's signal has? If that is not the intent why would you ever enter an mis-matched ratio? Is it just there because if you were to use the offset feature, but wanted to maintain an original intended aspect, you have to tell it what that is so it can stretch to fill it?
There are also a ton of 4K source files, presumably because the CP2220 had a 4K upgrade path or compatibility to read 4K signals... as a 2K house with no 4K signal sources at this time... those are, i assume, completely irrelevant to us?
We do often take the shortcut in DCPomatic of using non-standard DCP containers such as 166 or 138 when generating preshow content (I know this won't work on every projector out there), but we use those with the standard flat source files and it behaves as expected. Perhaps it has an impact on where other values "start" such as the screen file corners, or scaling corners, if you were to tell it an exact grid to match whatever container you were playing? In fact i'm not even 100% sure one can think of the "container" and the "signal" resolution as interchangeable here.
I'm relatively comfortable within most of the other channel settings, but Source File has always been slightly confusing given those extra options and coming from a non DCI background, and the manual does not illuminate the intent much other than to say that the source file dimensions should always match the incoming signal.
Perhaps if we were using sources that needed the offset feature, or other resolution/ratio ALT sources on the regular this would become more obvious, but as it is set up, all our non-blu-ray ALT sources go through a decimator MD-HX that somewhat imposes the preferred EDID and always translates to 1080p60 at the PIB board DVI input. So really we only find ourselves needing the Flat, Scope, Custom, and HD square pixel source files.
The letterbox tickbox was at the root of why our DCI 166 channel was not quite correct for eons. Used to never be able to see the edges of a 166 test pattern until I started digging a little deeper a while ago. I didn't even know the Netflix 166 chart had border lines for a while when I was learning. *facepalm* Luckily 166 is a pretty rare format these days.
Our 2k CP2220 has a ton of differing grid size source files populated, either from factory or from past users. Most of which seem completely irrelevant when running 2K F/S/Custom DCPs or 1080p alt content.
Separately, the source file setup has that tickbox for "Letterboxed", and lets you specify an intended aspect ratio (that may differ from the pixel grid that is entered), but the naming of that feature seems problematic cause it seems to have the capacity be relevant to pillar-boxing too? I assume if you don't want any pixel stretching or squishing you always set the source aspect to match the signal pixel grid you entered, unless you are doing some offset perhaps.
Is my understanding correct that when the grid ratio (after any offsets) and the "specified" source aspect ratios match, that is what is considered "square pixels". And if they are mis-matched in any way effectively you are manipulating the pixels to non-square (an expression, but that is the terminology in use).
Is the source aspect ratio setting (flat/scope/or manually entered) intended as a channel tool to allow you to stretch one source into a different aspect ratio than it's signal has? If that is not the intent why would you ever enter an mis-matched ratio? Is it just there because if you were to use the offset feature, but wanted to maintain an original intended aspect, you have to tell it what that is so it can stretch to fill it?
There are also a ton of 4K source files, presumably because the CP2220 had a 4K upgrade path or compatibility to read 4K signals... as a 2K house with no 4K signal sources at this time... those are, i assume, completely irrelevant to us?
We do often take the shortcut in DCPomatic of using non-standard DCP containers such as 166 or 138 when generating preshow content (I know this won't work on every projector out there), but we use those with the standard flat source files and it behaves as expected. Perhaps it has an impact on where other values "start" such as the screen file corners, or scaling corners, if you were to tell it an exact grid to match whatever container you were playing? In fact i'm not even 100% sure one can think of the "container" and the "signal" resolution as interchangeable here.
I'm relatively comfortable within most of the other channel settings, but Source File has always been slightly confusing given those extra options and coming from a non DCI background, and the manual does not illuminate the intent much other than to say that the source file dimensions should always match the incoming signal.
Perhaps if we were using sources that needed the offset feature, or other resolution/ratio ALT sources on the regular this would become more obvious, but as it is set up, all our non-blu-ray ALT sources go through a decimator MD-HX that somewhat imposes the preferred EDID and always translates to 1080p60 at the PIB board DVI input. So really we only find ourselves needing the Flat, Scope, Custom, and HD square pixel source files.
The letterbox tickbox was at the root of why our DCI 166 channel was not quite correct for eons. Used to never be able to see the edges of a 166 test pattern until I started digging a little deeper a while ago. I didn't even know the Netflix 166 chart had border lines for a while when I was learning. *facepalm* Luckily 166 is a pretty rare format these days.
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