priority [ATSC Semantics]
The priority is a 8-bit unsigned integer field in an ATSC AC-3 descriptor This is a 2-bit field that indicates the priority of the audio service.
valid priority field coding
| Bit field | Meaning |
| 1 / 0x01 | Primary Audio |
| 2 / 0x02 | Other Audio |
| 3 / 0x03 | Not Specified |
Ref: ATSC A/52, Table A.3.7
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