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system_clock_descriptor (MPEG-2)

This descriptor carries information about the system clock used to generate the timestamps in the transport stream. The external_clock_reference may be set to '1' if an external clock was used to generate the timestamps./p>

If the accuracy of the system clock is more accurate than the required 30 parts per million, the accuracy of the clock can be communicated by encoding the accuracy in the clock accuracy fields.

The accuracy of the system clock is expressed as:

clock_accuracy_integer x 10 10-clock_accuracy_exponent ppm
(MPEG-2 equation 2-26)
descriptor syntax
syntaxbit index# of bitsmnemonic
descriptor_tag0811 / 0x0B
descriptor_length88uimsbf
descriptor_tag0811 / 0x0B
descriptor_tag0811 / 0x0B
external_clock_reference_indicator161bslbf
reserved171'1'
clock_accuracy_integer186uimsbf
clock_accuracy_exponent243uimsbf
reserved275'11111'
legend

See: Descriptors Generally

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