Entertainment Center: TVs, Stereos, VCRs and DVDs - HD Resolution?
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Philossifer
11-04-07, 07:23 AM
When I tune my HD TV to HD broadcasts, I get these numbers on the display, depending on which channel I'm watching (1080i or 720p or 480i)
It probably has to do with the HD resolution (right?) Is there a website that describes in detail what those numbers mean; or can somebody here explain?
I'm confused; it seems the 720p provides a slightly better picture than the 1080i broadcasts...........
Thanks,
Phil
It probably has to do with the HD resolution (right?) Is there a website that describes in detail what those numbers mean; or can somebody here explain?
I'm confused; it seems the 720p provides a slightly better picture than the 1080i broadcasts...........
Thanks,
Phil
Integrator97
11-04-07, 10:02 AM
Try
http://www.cnet.com/4520-7874_1-5137915-1.html
http://www.cnet.com/4520-7874_1-5108580-3.html
Quote from the 2nd article:
"1080i and 720p. One is not necessarily better than the other; 1080i has more lines and pixels, but 720p is a progressive-scan format that should deliver a smoother image that stays sharper during motion."
The " i " is for interlace, meaning your tv puts up 540 even numbered lines at one time, then 540 odd numbered lines, then back to even.
The "p" is for progressive scan, which scans the lines to the screen very fast, top to bottom.
http://www.cnet.com/4520-7874_1-5137915-1.html
http://www.cnet.com/4520-7874_1-5108580-3.html
Quote from the 2nd article:
"1080i and 720p. One is not necessarily better than the other; 1080i has more lines and pixels, but 720p is a progressive-scan format that should deliver a smoother image that stays sharper during motion."
The " i " is for interlace, meaning your tv puts up 540 even numbered lines at one time, then 540 odd numbered lines, then back to even.
The "p" is for progressive scan, which scans the lines to the screen very fast, top to bottom.
Rick Johnston
11-05-07, 04:53 AM
The terminology is a throwback to CRTs (picture tubes). They display a single point of light -- the electron beam -- that zig-zags across the screen horizontally from top to bottom. When it moves from left to right it excites the phosphors to light a single line of the TV picture. It then returns to the left without drawing anything, skips line two and draws the third line, fifth line, seventh line, and so on. It completes the "odd line" pattern in 1/60th of a second and returns to the top. In the next 1/60th of a second it draws the even lines. The odd and even screens are called fields.
These two interlacedfields make one frame of video. There are 30 frames of video in one second. (okay, actually 29.97, but that's another discussion ...)
NTSC (standard-def analog) video has 525 horizontal lines of resolution, so each field contains 262.5 lines. In today's terms, it would be called 525i.
The reason this was done was to conserve bandwidth, and to take advantage of the fact the the phosphors in a CRT screen continued to glow after they were excited. (Similar to our eyes' retinal retention, which allows us to perceive a movie as a continuous picture rather than a series of stills.)
If the fields of video were eliminated and the electron gun simply drew all of the lines in order from top to bottom, good ol' SDTV would be 525p. It still happens 30 times per second, so technically there is nothing different about the picture other than the slice of time it displays (1/60th x 2 versus 1/30th).
A 720p picture displays all of its 720 horizontal lines 30 times in one second.
A 1080i picture also displays all of its 1080 lines 30 times in one second, but it does so by displaying the odd field for 1/60th, then the even field for 1/60th.
480i and 480p are throwbacks to the 90's and the convergence of computers and TV. Three reasons why they arrived at that standard:
-- Less data would be required to produce a viewable picture on the comparatively slower digital systems of the day.
-- The first 21 lines of a 525-line display don't contain picture information. They are reserved for closed captioning, time codes, and other data.
-- CRTs are notoriously sloppy and cannot be counted on to display the entire raster on the screen. As they age, overshoot becomes an issue and a portion of the picture is display behind the bezel or off the screen altogether. It was determined that 480 was all that was needed to display a digital picture on a CRT.
These two interlacedfields make one frame of video. There are 30 frames of video in one second. (okay, actually 29.97, but that's another discussion ...)
NTSC (standard-def analog) video has 525 horizontal lines of resolution, so each field contains 262.5 lines. In today's terms, it would be called 525i.
The reason this was done was to conserve bandwidth, and to take advantage of the fact the the phosphors in a CRT screen continued to glow after they were excited. (Similar to our eyes' retinal retention, which allows us to perceive a movie as a continuous picture rather than a series of stills.)
If the fields of video were eliminated and the electron gun simply drew all of the lines in order from top to bottom, good ol' SDTV would be 525p. It still happens 30 times per second, so technically there is nothing different about the picture other than the slice of time it displays (1/60th x 2 versus 1/30th).
A 720p picture displays all of its 720 horizontal lines 30 times in one second.
A 1080i picture also displays all of its 1080 lines 30 times in one second, but it does so by displaying the odd field for 1/60th, then the even field for 1/60th.
480i and 480p are throwbacks to the 90's and the convergence of computers and TV. Three reasons why they arrived at that standard:
-- Less data would be required to produce a viewable picture on the comparatively slower digital systems of the day.
-- The first 21 lines of a 525-line display don't contain picture information. They are reserved for closed captioning, time codes, and other data.
-- CRTs are notoriously sloppy and cannot be counted on to display the entire raster on the screen. As they age, overshoot becomes an issue and a portion of the picture is display behind the bezel or off the screen altogether. It was determined that 480 was all that was needed to display a digital picture on a CRT.