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SMPTE / st429-20

Public CD of SMPTE ST 429-20 1ED
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Generic Picture Essence Descriptor #15

Closed jpviollet closed 3 years ago

jpviollet commented 3 years ago

In the generic picture essence descriptor:

. Gamma item in ST377:2004 is called Transfer Characteristic item in ST377-1:2019. Also, there is no default value in ST377-1:2019 (see G.2.22: “The default value is not defined”) compared to ST377:2004 that states (see E.2.27): “If the property is not present, its value shall be assumed to be the Universal Label identifying SMPTE 170M colorimetry and transfer.” We may want to indicate all this, especially as Gamma item is specified as “should be used in D-Cinema applications” in ST429-4.

. Coding Equations and Color Primaries items do not exist in ST377:2004. Not sure if we should indicate that they “should not be present” with the usual NOTE.

palemieux commented 3 years ago

@jpviollet Revised draft at https://smpte.sharepoint.com/sites/21DC-DocumentMaintenance/_layouts/15/DocIdRedir.aspx?ID=21DC-2062321792-57433

jpviollet commented 3 years ago

My apologizes, I realize that in ST377:2004, the correct item name is actually "Capture Gamma" - Gamma seems more corresponding to the value of the Capture Gamma item, explaining most likely why Annex E.2.27 and ST429-6 are only speaking about "Gamma". We should then correct the second example in section 6.5 to speak about "Capture Gamma" instead of "Gamma".

About the newly added section 5.13, it would indeed solve the remainder of this Github comment, with maybe a change in NOTE 2, as it does not feel right to speak about Transfer Characteristics in liaison with ST377:2004 (as it is called "Capture Gamma" in this version), despite the fact that we clarify this name difference in section 6.5. We may have to repeat this name change in section 5.13 too for clarity maybe, something like:

"NOTE 2: SMPTE ST 377:2004 specified conflicting default values for the Transfer Characteristic item (named "Capture Gamma" in ST377:2004)"

palemieux commented 3 years ago

Fixed at https://smpte.sharepoint.com/:w:/s/21DC-DocumentMaintenance/EQQ7z9QmkB5FpI-6DUq2M40Bel9AGD3ipTzGVA9lrE3LvQ?e=MSvyh8

jpviollet commented 3 years ago

This revision resolves my comment, thank you.