On 2014-01-18 01:14 PM, Peter Vince wrote:
Stephen Scott has just mentioned his involvement in the TV industry in
the USA, with its problematical 29.97 Hz frame-rate.
Lets not propogate the notion of a "29.97 Hz" rate, especially in the
the context of this LEAP_SECS list. "29.97" is a commonly used NAME,
shorthand for the correct NTSC rate - 30000/1001 Hz. This inaccurate
representation has been the source of much confusion and bad
implementations over the years.
I also work in the TV industry, but in the UK where we are lucky to
have a nice integer 25 Hz rate.
But that 25 doesn't divide evenly very well :-)
Although historically we still had a problem with leap seconds, as
the 625 PAL system had a 4-frame ("8-field") sequence (due to the
exact colour subcarrier frequency being offset from a multiple of line
frequency to avoid static patterning on monochrome displays), and so
there were three and one-eighth of these 4-frame sequences per second.
When editing, this frame-sequence had to be maintained, else there
would be a small sideways jump when the replay machine kept the signal
synchronous with the colour subcarrier phase.
Anyway... those problems have largely gone away now that we have
stopped broadcasting the analogue PAL signal.
The "we" you're referring to is Europe, I think, but other parts of the
world are still broadcasting analogue. Standards rarely escape their own
legacy.
I was wondering if Stephen, or anyone else, has any information about
the possibility of 60 Hz countries changing the nasty NTSC-based 29.97
Hz frame rate to a nice integer 30 Hz rate, as I believe analogue has
also all but been switched off in the USA too (no knowledge of other
60 Hz countries.)
Say "good morning" to the four emperors - UTC, film (24hz), PAL, and NTSC.
-Brooks
Regards,
Peter Vince
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