Add PQ (HDR) metadata support to AS-11 X1, X5, X10

[thomasheritage]

• At the time AS-11 X1 was written there was no clear answer to the PQ metadata that needed to be included in the MXF file, or how to include it. Therefore these mechanisms are not specified in X1.
• There are now solutions used in IMF for carrying this metadata (some is carried in the MXF and some in the XML of the IMF package, we believe).
• There shouldn't be anything in X1 that prohibits PQ metadata being carried in an X1 MXF file. However, it may be the case that not all the mechanisms are defined.
• It would be good to know what PQ metadata is required for the scenario supported by X1 and whether there are established practices for how to include this in MXF (when not using IMF). Such a practice could then be adopted in X1.

[thomasheritage]

• This would apply to all AS-11 X specs that use HDR
• We could add a Note to explain the situation to at least point this out to implementers
• This would advise that you consider including the "Mastering Display Color Volume Metadata" in the Picture Descriptor -- as defined in IMF App2e. This should be sufficient re metadata needed for PQ HDR signals (MaxFALL and MaxCLL appear in App2e CPLs -- these could not be added easily in AS-11 X specs but they should not be needed)
• These comments should address all the uncertainties in the description of this issue (above)