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Raw uncompressed bandwidth of 1080i HD?

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Old 11-28-2009, 11:36 PM   #16  
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I think perhaps you misinterpreted what I wrote. I did not claim that there were no studio VTRs that supported those formats; obviously there are. What I did state is that our facility has quite a bit of studio equipment that does not -- in particular, several graphics generators and some processing gear.

-- Jeff
Yes, I did miss that. Sorry about that. That is funny that your studio doesn't have some of the gear that supports that, because we are just the opposite. We should team up and make a powerhouse facility. LOL
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Old 12-07-2009, 12:55 PM   #17  
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The actual frame size for 1080i/p is 1920x1088. The extra 8 scan lines are blank and are discarded by the receiver before the images are sent to the display. They are needed because of the requirements of MPEG compression which require the "dimensions" in both directions to be divisible by 16.
Minor point:

That's an MPEG2 requirement. MPEG4 doesn't have this limitation since it has variable-sized squares.
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Disregarding the fact that progrssive scan has been found to be a little easier to compress using MPEG-2, 1080p/30 requires the same bandwidth that 1080i requires and 1080p/24 takes less bandwidth than 720p/60. The oft quoted factoid that 1080p requires too much bandwidth for OTA broadcasting is nothing more than a myth that won't die, propagated by people who do not understand that progressive scan involves multiple frame rates.
Is anybody using 1080p/30? I've never found any stations that are doing that. The HD stations always read 720p or 1080i.

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.

(shrug). Oh well.
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Old 12-07-2009, 12:58 PM   #18  
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Y1080p/24 especially, and 1080p/30 to a lesser degree, have readily perceived flicker on a number of displays;
Why would a modern LCD display flicker?

Movies run at 24 frames (or slower in older films), and they don't flicker. How come?
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Old 12-07-2009, 01:01 PM   #19  
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Originally Posted by 1080PsF View Post
SD is
858 * 525 * 29.97 * 20 = 269,999,730 bits or 270Mbps

720 HD is
1650 * 750 * 59.94 * 20 = 1,483,515,000 or 1.4835Gbps

1080 30 frame HD is
2200 * 1125 * 29.97 * 20 = 1,483,515,000 or 1.4835Gbps
Where did you get those numbers? They don't seem to match the known DTV standards of 720 or 704x480; 1280x720; 1920x1080
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Old 12-07-2009, 03:48 PM   #20  
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Why would a modern LCD display flicker?

Movies run at 24 frames (or slower in older films), and they don't flicker. How come?
Some people do perceive flicker with 24fps film... and whether they are conscious of it or not, that is part of the "film look". As it happens, I am aware of it... which is one reason I seldom go to movie theatres, unless I want to leave with a screaming headache. The other reason is, I make better and cheaper popcorn.

I almost overlooked the original question about why an LCD monitor would flicker, and I can think of several reasons. Compared to a CRT monitor with relatively persistent phosphors, an LCD is capable of extremely rapid level changes. Depending on the signal you are displaying, and how it interacts with the original frame rate and the display's refresh rate, you can easily get discernable flicker effects that would have been masked on a CRT.


-- Jeff

Last edited by DTV_Engineer; 12-07-2009 at 03:54 PM.. Reason: Remembered part of the original question
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Old 12-07-2009, 04:18 PM   #21  
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Movies run at 24 frames (or slower in older films), and they don't flicker. How come?
The frames are displayed on the TV multiple times. The result is known as 2:3 pulldown. A TV projector has a special shutter.

In a theater, the image is projected for a longer period of time. The black between frames is so short that your eye can't perceive it.

Another term for the motion artifacts of the film look is judder.

http://en.wikipedia.org/wiki/Telecine#2:3_pulldown
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Old 12-07-2009, 04:40 PM   #22  
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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.

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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.

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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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Old 12-10-2009, 11:42 PM   #23  
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Where did you get those numbers? They don't seem to match the known DTV standards of 720 or 704x480; 1280x720; 1920x1080
Your orig question is asking about uncompressed HD. These are the real uncompressed numbers of HD. Not broadcast but the true bandwidth it takes to move an HD signal around before it gets squeezed down for broadcast.
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Old 12-11-2009, 03:40 PM   #24  
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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.
1080/60i - approximately 10 Mbit/s
480/60i - ~4.5 Mbit/s
480/60i - ~4.5 Mbit/s

Now eliminate the two subchannels and you get:
1080/60p - 19 Mbit/s

Plenty of space. "There was not enough room" is not the answer IMHO. "The processing power was not available in 1995" is probably a better reason for why it's not in the ATSC spec
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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.
That's weird. I'm surprised DTV boxes are able to understand that format, and I'm also surprised the FCC lets them send a non-ATSC-compliant format.

Does ATSC have a provision for 240i or 240p low-definition broadcasts?
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Old 12-11-2009, 03:41 PM   #25  
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Your orig question is asking about uncompressed HD. These are the real uncompressed numbers of HD.
And where did you get those numbers?
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Old 12-12-2009, 12:14 AM   #26  
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Originally Posted by electrictroy View Post
1080/60i - approximately 10 Mbit/s
480/60i - ~4.5 Mbit/s
480/60i - ~4.5 Mbit/s

Now eliminate the two subchannels and you get:
1080/60p - 19 Mbit/s

Plenty of space.
Nonsense!
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Old 12-12-2009, 10:05 AM   #27  
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1080i/30 occupies the entire 19Mbit span of a 6 MHz channel.

I can be bit starved down to 12-13 Mbits but the picture is noticable degraded.

1080p/60 would require 38 Mbits for excellent definition, twice the band width of 1080i/30.

720p/60 needs about 14 Mbits so a 720p channel can easily share a channel with a 480p signal which needs about 4 Mbits optimally.

WE have a local CW/MYTV/UNI digital with 2 720p's and a 480i. Needless to say the 720ps are a bit soft from running about 8 Mbits, but it is still noticably better than 480i.
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Old 12-12-2009, 06:09 PM   #28  
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WE have a local CW/MYTV/UNI digital with 2 720p's and a 480i. Needless to say the 720ps are a bit soft from running about 8 Mbits, but it is still noticably better than 480i.
We're just now setting up a brand new box by Harris called a NetVX... it's basically a card frame you populate with all of the devices you need to create a multi-program ATSC transport stream (there are other applications for it, but that's what a broadcast station would use it for). Ours happens to have a pair of HD encoders and a multiplexer to combine their outputs with PSIP data to produce a SMPTE 310 output to send to the transmitter. It's an impressive device: we are finding that we can fit two 720p/59.94 signals into one channel at about 9 megabits per second each, and the subjective quality is at least as good as our older Tandberg E5821 encoders running at 14 or 15... even with rapid and highly random motion.

Several recent posts have correctly observed that broadcast 1080i runs at 30 frames per second (actually, 29.97); 1080p/60 would yield four times the data rate of 1080i/30, not double. Still, it's a moot point: even this brand new NetVX can only fit two HD streams into an ATSC signal if they are both 720p/59.94.

But as several folks have already observed, none of this is pertinent to the original question about the bandwidth (which would be the data rate) of raw uncompressed 1080i... and per SMPTE 292M, it's 1.485Gb/s.

-- Jeff
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Old 12-12-2009, 06:27 PM   #29  
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And where did you get those numbers?
Those are numbers I deal with everyday I work. Those numbers include horiz. and vert. blanking info. I believe I sent you a PM with a link to a paper I wrote about this.
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