[time-nuts] Measuring TV delays

[Bill Hawkins]

IIRC, the reason why NTSC has an almost 30 fps rate is that early
vacuum tube TV sets could develop heater-cathode leakage that
would put a black "hum bar" in the picture. Almost 30 allows the
bar to move through the picture in a 60 Hz power distribution
system. Seems like Europe would have had that problem.

No need for it now, but it's like the QWERTY keyboard . . .

Bill Hawkins
 

-----Original Message-----
From: Magnus Danielson
Sent: Thursday, January 02, 2014 12:15 PM

So, in the US and other 30000/1001 frames per second countries (formerly

NTSC), encoded time is not going to be useful for precision work. For us

in the 25 frames per second world, we only need to jam for leap-seconds 
and DST change-overs, but that is enough of an upset, but can be more 
easily predicted with only a few handful of bits extra information.

I prefer using MLS measurement for audio delay measurement. If you do it

right, you get 20,833 us step resolution, as a result of the 48 kHz 
sampliung clock. MLS delay measurement is trivial using the Analog 
Precision test-set.

Cheers,
Magnus
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