payload_unit_start_indicator [MPEG-2 Semantics]
The payload_unit_start_indicator is a 1-bit boolean field in an MPEG-2 transport packet header that, when 'True' or '1', indicates that a payload unit starts in the current packet. If no payload unit starts in a packet, payload_unit_start_indicator is set to 'False' or '0'.
If the packet carries packetized elementary streams, a PES payload is the payload unit. If the packet carries private table sections, a payload unit is a table section.
If the packet carries a packetized MPEG-2 private table section, the first byte in the payload represents the pointer_field, which gives the location of the first byte of the private table section.
ATSC:As a general rule, ATSC PSIP table sections begin in a packet where payload_unit_start_indicator is set to 1, with the pointer_field in the first byte of the packet payload, and pointer_field is set to '0.'
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