[mythtv-users] NTSC refresh rate? 59.97 or 60Hz?

[Doug Larrick]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

William Munson wrote:
> I am in the process of improving my custom mode line and want to make 
> sure my refresh rate is correct. What is the correct value for a NTSC tv 
> signal?

For NTSC, 59.94 Hz is the field rate, 29.97 Hz is the frame rate.  This
was changed from 60/30  with the advent of color TV to prevent
interference between the luminance and chrominanace portions of the
signal.  The Wikipedia article http://en.wikipedia.org/wiki/Ntsc has an
explanation.

My understanding is this refresh rate is carried over into ATSC modes to
prevent the very same interference with existing analog stations.  My
further understanding is that once analog NTSC broadcasts are
eliminated, broadcasters will have the option of using 60/30 Hz once again.

- -Doug
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.6 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFGelNff1/38+/zqMERAgkdAKCCjuji2zB08YoSjUC6Is+4NB/bpgCffreg
pt5W+AnWFv4nJZNLYrPnxI4=
=Q9Sv
-----END PGP SIGNATURE-----