[LEAPSECS] TV frame-rate in 60Hz countries

[Brooks Harris]

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

>

>

>

> _______________________________________________

> LEAPSECS mailing list

> LEAPSECS at leapsecond.com

> http://six.pairlist.net/mailman/listinfo/leapsecs


-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://six.pairlist.net/pipermail/leapsecs/attachments/20140118/222f7290/attachment.html>