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

[Ken McGaugh]

Daniel A. Fort wrote:
> 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)

Your description is excellent and I think I'm starting to understand
this.  But I think there is conflicting terminology going on and I'm
trying to get it straight.

The DPX spec, the KeyKode doc, and SMPTE 254 all refer to the "perf offset"
as the "00" part of your example above, which is the number of perfs since
the last valid barcode.  You are referring to "perf offset" as the "p1"
bit at the end of the example, which is the relative position of the zero-frame
with respect to the zero-frame reference mark, correct?

I agree that this number should be included in the KeyCode attribute, although
I think there will need to be some human intervention in getting these numbers
into our exr's since I don't see a corresponding number inside any cineons or 
dpx
scans.  But I don't think it should be named perfOffset since that name is 
already
taken.  Any suggestions?  How about refMarkPos?


> 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."

This is why the filmFormat attribute will be a seperate string attribute.
It therefore can take any value you want.  And since we are going to add
a perfsPerFrame field to the keyCode attribute it isn't necessary to have
filmFormat for keyCode computations.

--Ken