Re: [Openexr-devel] Re: [Openexr] KeyKode offsets

[Daniel A. Fort]

> > This is all good information to help understand why perf offset is so 
> >  important to scanned images. I think the developers are on the right 
> >  track for including it in the key code field for OpenEXR.
>
> When you say "perf offset" above, are you talking about this second 
> number Thomas suggests, or are you just referring to the existing perf 
> offset number already in Florian's proposed KeyCode class?  Should we 
> add another offset field, and if so what should we call it?

I'm referring to Florian's KeyCode class. Once again, an example key 
number would be something like:

FN 12 3456 7890 + 00 p1

where p = perfOffset
values ranging from p1 to p(number of perforations per frame)

Note that 16mm is only 1-perf per frame so the perf offset isn't 
significant while IMAX will range from p1 through p15.

Perhaps allowing for a perfOffset value of p0 could mean that it wasn't 
entered in the scanning log. This should be okay for most film 
formats--with the exception of 35mm 3-perf.

The second number Thomas suggests seems to be something needed for the 
scanning equipment but is probably not needed to identify the frame. I 
believe that the scanning equipment Thomas is referring to will read 
the barcode on the film and automatically determine any discontinuous 
key codes, but I'm just speculating--maybe Thomas can enlighten us.

> I would aso suggest having the perfsPerFrame() default to 0 and leave
> the interpretation of that to the the software reading the keycode
> (with the assumption that it would be 4 in most all cases).

Of a film frame cannot be 0 perfs per frame, but that could be used by 
the software reading the key code to default to a value that is set in 
the preferences--it might not necessarily be 4-perf 35mm.

One more thought on the film format attribute--there are many formats 
of 4-perf 35mm. For example I've worked with 35mm Full Frame, Academy, 
Flat 1.85, Scope 2.35, Super 35, Super 1.85, European Standard 1.66 and 
1.77 for transfer to HD 16x9. That's why I suggested making the film 
format attribute "free form."

--Dan