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Old 12-07-2009, 04:40 PM   #22  
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Join Date: Jul 2005
Location: Pointe-Claire QC
Posts: 2,865

Originally Posted by electrictroy View Post
Minor point:

That's an MPEG2 requirement.
Broadcast TV uses MPEG2, so the comments concerning 1088 lines for both 1080i and 1080p are valid as is the comment that 720i does not exist under the ATSC standard as it applies to North America.

Is anybody using 1080p/30?
Not that I have seen, but it could happen as newer broadcast equipment becomes available. Disregarding any differences in ease of compression, 1080p/30 takes the same bandwidth as 1080i. Note also that it is unnecessary to specify frame (or field) rate for interlaced broadcasting because in North America it is always 30 (or 29.97) frames per second.


As for 1080p/60, there should be enough bandwidth. If they can do 1080p/60i, plus two subchannels, they ought to be able to kill the subchannels & use those bits to switch from 60i to 60p.
1080/60i is only 30 1920x1088 frames per second while 1080/60p is 60 1920x1088 frames per second, so 1080p/60 takes twice the bandwidth that 1080i takes. And that bandwidth is consiiderably more than one 1080i sub-channel plus two or three 480i/p sub-channels. Your math is faulty.

Not all of the 18 ATSC formats (actually 36) are in use at present but there are some stations that are broadcasting non-standard formats.

The following formats are the ones currently being used in the Plattsburgh NY-Burlington VT market. All rates are specified in frames per second.

1920x1080i/30: WCAX(CBS), WPTZ(NBC), WETK(PBS), WCFE(PBS).

1280x720p/60: WVNY(ABC), WFFF(FOX)

All broadcast 1 or more SD sub-channels, as follows:

704x480i/30 16:9 Widescreen: WCAX

704x480i/30 4:3 standard screen: WPTZ, WVNY, WETK(2), WCFE(3)

528x480i/30 4:3 Standard Screen: WFFF

Note that this last format is non-standard but is used by WFFF to broadcast its CW channel. (Note that 528 is 3/4 of 704.) This sub-channel is noticeably blurry compared to all of the other SD sub-channels.
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