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SMPTE / ST377-1-full-revision

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DataStream vs DataValue #21

Open HaroldHallikainen opened 4 years ago

HaroldHallikainen commented 4 years ago

https://registry.smpte-ra.org/view/draft/docs/Register%20(Types)/Individual%20Types%20entries%20(EXCEPTIONS%20etc)/#datavalue-and-variablearrays

“DataValue” and “VariableArray”s An instance of the “DataValue” Type is encoded “in-line” – it is simply a piece of binary data whose structure is not defined in the Types Register.

Note that “DataStream” in ST 377-1:2011 appears to be an error – it should say “DataValue”.

Although “DataValue” is modelled as a “VariableArray”, in an MXF file there is no eight-byte header. This is exceptional behaviour – a “VariableArray” is ordinarily implemented in MXF as an “array” which has an eight-byte header. However, note that the AAF toolkit / SDK does expect “DataValue” to have an eight-byte header when performing MXF reading / writing – this means that if this Type is used in an MXF file then the file will not be compatible with the AAF toolkit / SDK.

TatsujiYamazaki commented 2 years ago

There are two kind of implementation, with or without the eight-byte header. (some description on RDD 48)

  1. To ask 30MR to take this action first.
  2. Bruce-san to add an appropriate comment on Phase-1.