Talk:720p
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"NBC uses the tagline "the nation's finest high-definition standard" in advertising its 720p programming."
- But the NBC website claims that all NBC HD broadcasts are in 1080i:
- "NBC broadcasts HDTV in the 1080i format, which provides the highest possible resolution to our audience." [1]
- Lee M 17:24, 12 Dec 2004 (UTC)
- I see that the reference to NBC has now been changed to Fox. It's all a bit academic to me anyway because I'm in the UK... Lee M 17:08, 17 Dec 2004 (UTC)
which one is better 720p or 1080i? cheers
- There is a consensus building that 720p is better for moving images, whereas 1080i is better for video with a lot of still or near-still footage. Thus, movies, nature, and drama content are better in 1080i, like on PBS-HD and NBC. Sports are better in 720p, like on ABC, Fox, and ESPN-HD. Obviously, 1080p60 would be the best of both worlds, but too bad, we can't have it. --Locarno 22:56, 9 Feb 2005 (UTC)
- 1080p60 just requires more efficient data compression. They'll get there eventually, and then they'll start working on even higher definition systems.
Interesting that the ATSC saw the two systems as content-specific, but the Networks, possibly for financial reasons, have each opted for just one. It'll be interesting to see what happens when Sky HD launches in the UK.... incidentally (or perhaps not) Britain will use 1080i25 and 720p50, meaning that despite having the same picture resolution as the US there'll still be frame-rate conversion issues to contend with. Not to mention the whole thorny question of up-and-down converting from PAL and NTSC.Lee M 02:50, 8 Mar 2005 (UTC)
- 1080p60 just requires more efficient data compression. They'll get there eventually, and then they'll start working on even higher definition systems.
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[edit] Television resolution chart
How does one edit the Television resolution chart on this page? It contains incorrect references to "240i" and "288i" In fact, these are progressive, (240p) even when displayed on NTSC and PAL sets. Algr 05:01, 22 February 2006 (UTC)
[edit] Fox Revert
Fox uses 720p, but it is possible that some of their affiliates convert this to 1080i before broadcast. Many sets do a poor job with native 720p, and look much better if such a signal is converted to 1080i by something else first. Algr 05:49, 30 April 2006 (UTC)
[edit] citation needed?
Some U.S. broadcasters use 720p60 as their primary high-definition format; others use the 1080i standard.
We already have references showing that both 720p and 1080i are in use. Algr 07:05, 13 August 2006 (UTC)
[edit] Interlace is misunderstood ...
These 2 sentences contain gross misunderstandings ...
Progressive scanning reduces the need to prevent flicker by filtering out fine details, so spatial (sharpness) resolution is much closer to 1080i than the number of scan lines would suggest.
and
The main tradeoff between the two is that 1080i may show more detail than 720p for a stationary shot of a subject at the expense of a lower effective refresh rate and the introduction of interlace artifacts during motion.
Interlace doesn't "filter out fine details". Some interlace systems may low-pass filter vertical detail (only) to a very slight degree, in order to eliminate interline twitter that occurs when the subject includes narrow horizontal stripes that approach the vertical field resolution. 1920 horizontal pixel resolution is definitely greater than 1280.
Interlace doesn't introduce artifacts during motion. Interlaced video is quite good at capturing and portraying motion. Interlace artifacts are only introduced when interlaced video is converted to progressive scan.
- That is completely incorrect. Interlacing can introduce spatio-temporal aliasing (edge flicker, line crawl, etc) unless video is properly low-pass filtered in the vertical dimension. Interlacing samples space-time at half the rate of progressive scanning.
Don - both of us are guilty of not signing our posts. Clearly you know what you are talking about... but I don't completely agree with your statements. As you know, aliasing can occur when you digitally sample something that has information at a frequency greater than half the sampling frequency (the Nyquist frequency). Interlace has half of the vertical resolution per field, but the same vertical resolution per frame as progressive scan. If the picture being captured by the video camera contains information with a lot of detail, artifacts can occur. However there are many reasons why this is not normally a problem. The camera would have to be in focus on the object, otherwise the lack of focus serves as a low-pass filter. If the object or camera are in motion, the motion blur low-pass filters the detail. The accuracy of the lens and the sensor (CCD, CMOS) can low-pass filter the detail. In general, most scenes being shot don't have the type of image detail that causes visible artifacts. Very high-end cameras filter the vertical resolution in order to reduce interline twitter, but most cameras don't... it isn't necessary for most situations. Finally, I would have to say that interlacing samples space-time at the same rate of progressive scanning, to be fair. Space is sampled at half the quantization level at twice the frequency... but the trick of offsetting the samples between frames by on line (spatially) gives the eye a moving average of the detail and the motion. If the object is moving, your eye gets updated information at a better refresh rate. If the object isn't moving, your eye still gets all of the detail of the full frame (due to the way the human visual system works). I've got nothing against 720p... it's great stuff. Progressive scan has advantages over interlace, particularly when it comes to editing (like slow motion detail), or display on progressive scan displays (which are all the rage for TVs these days, plus they are a part of every PC). But interlace is a technique that works, even if it isn't well understood. Tvaughan1 23:52, 26 October 2006 (UTC)
