[time-nuts] Measuring TV delays
David J Taylor
david-taylor at blueyonder.co.uk
Fri Jan 3 15:28:27 UTC 2014
From: Magnus Danielson
There are several potential time-signals, but I would say it would be a
bit hard to verify their traceability, which makes the exercise difficult.
The MPEG-2 Transport Stream have PID timestamps for every channel.
However, there is really no good TAI/UTC traceability in them. Also,
re-stamping is used to cover up for delay variations.
VITC might be present, and might provide local time, but for NTSC
countries there is a frequency error only partly covered in the
drop-frame compensation which causes a deviating display-time from
actual local time.
Caption can also carry time, but there is no guarantee it has a sane source.
Cheers,
Magnus
===============================
Many thanks, Magnus. There seems to be a lot of scope for experimentation
and discovery here! Excellent point about traceability!
David
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Email: david-taylor at blueyonder.co.uk
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