Question on picture resolution (1 Viewer)

andy_horton

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Most of my local subnets of course are in SD, 720×480. Comet shows 544×480. Tv show on has black bars on sides on Comet, but so does the show on Charge! and it shows 720×480. What is the difference in 544×480 and 720×480? Thanks
 

HoTat2

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Jun 12, 2012
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Most of my local subnets of course are in SD, 720×480. Comet shows 544×480. Tv show on has black bars on sides on Comet, but so does the show on Charge! and it shows 720×480. What is the difference in 544×480 and 720×480? Thanks
It means that Comet broadcasting at 544 x 480 has a lower native resolution and thus PQ, with pixels that are about 17% wider than they are taller within a 4:3 frame.

Whereas the subnets at the standard 720 x 480 resolution is higher and thus has a better PQ with pixels that are about 11% taller than they are wide within a 4:3 frame.

IOW, unlike 16:9 HD, neither of these 4:3 SD formats uses "square" pixels. But the 720 x 480 one has a higher resolution and thereby PQ.

How sharp your eyesight is to actually see this difference in resolution though, is another story of course.
 

Jim5506

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720X480 is wide screen SD (16X9).

544X480 is 4X3 SD, same as analog TV used to be.

Most pre HDTV programs were recorded or filmed in the 4X3 format so the info to display them wide screen just is not there, thus the black bars on the side unless they stretch the picture horizonally (YUCK).

Transmitting a 4X3 program in a 16X9 format can even register as 720X480 because the black side bars add blank pixels on both sides of the original picture.
 
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HoTat2

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Yes, that is if the SD frame is 16:9 ...

But you may have 4:3 frame SD material with 720 x 480 resolution with many broadcast subchannels and is the format used by the old standard DVDs of course.

The rule is 4:3 SD format material may be different resolutions below and including up to 720 x 480. However, 16:9 widescreen SD should never be less than 720 x 480.

The above being said though, when compared to the old NTSC standard, I've always had trouble fully understanding how the pixel count resolution of digital video today compares to the old TV line measurement ("TVL") of the analog era of the scanning CRT.

Back then for broadcast TV the "rule-of-thumb" was about 70% of the 480 horizontal lines, or 336, were considered "resolvable" due to imperfections in the interlace scanning process. And with a figure of about 80 TV lines per MHz of video bandwidth. The all-important horizontal resolution that really determined the picture's sharpness, came to about the same number of 336 for the vertical lines.

So if you were (lucky enough) to see a resolution chart or "test pattern" broadcast back then, with the familiar converging horizontal and vertical line "wedges." You would see an identical line count for both dimensions before the black and white transitions blended together into gray at around 330 lines each.
 

comfortably_numb

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Is the “HD” standard both resolution *AND* picture size? Or just resolution? I get into debates with a friend of mine over this sometimes.

For instance, a channel could have a high resolution but only display a 4:3 picture in the middle of the screen. So is that HD?
 

HoTat2

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Is the “HD” standard both resolution *AND* picture size? Or just resolution? I get into debates with a friend of mine over this sometimes.

For instance, a channel could have a high resolution but only display a 4:3 picture in the middle of the screen. So is that HD?
Both ...

But HD has higher resolution and a different "picture shape" or 16:9 aspect ratio ...

Not necessarily a different "picture size" as both 16:9 and 4:3 screens can technically cover the same sq. units of area. as demonstrated here with a 55" diagonal screen TV in 3 different aspect ratios.

television aspect ratio - Google Search:

Though this is for illustration purposes only. As I can't see anyone today making a 55" diagonal 4:3 screen.
 

comfortably_numb

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Both ...

But HD has higher resolution and a different "picture shape" or 16:9 aspect ratio ...

Not necessarily a different "picture size" as both 16:9 and 4:3 screens can technically cover the same sq. units of area. as demonstrated here with a 55" diagonal screen TV in 3 different aspect ratios.

television aspect ratio - Google Search:

Though this is for illustration purposes only. As I can't see anyone today making a 55" diagonal 4:3 screen.

So it has to be a higher resolution and 16:9 shape to be called HD?
 

Jim5506

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Technically yes, but the original Hogan's Heroes episodes were filmed in 4X3 aspect ratio and were transferred to HD video as 14X9 cutting a bit off the top and bottom of the film version to produce the shows in HD.

An old TV show originally on film in 4X3 can be transferred to video with a 16X9 frame that has a 4X3 HD window with all the original frame with black sidebars added to fill it to 16X9.

The actual frame sent to the TV is 16X9 HD, 1920X1080, but with black bars on the sides where the edge of the original film stopped.

HDTVs can interpret (upscale) a 3X4 image sent to them in various ways.

My Sanyo has the capability of either displaying it in original 4X3 aspect ratio or streching it to fit the 16X9 full screen or zooming it to fit the width which chops off the top and bottom of the image.

My Hitachi RPCRT TV can do 16X9 standard, expanded, zoom and 4X3 standard.

It all depends on the capability of your HDTV.
 
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Jim5506

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Vertical resolution @ 720 lines, but horizonal can vary widely and sometimes the pixels are not square.
 

Trip

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For whatever reason, my computer at home isn't letting me reply to messages here, so let me address this now that I'm at the office.

The ATSC standard only officially recognizes 640x480 and 704x480 for SD. Other resolutions may be supported by receivers (I've seen 352x480, 480x480, 528x480, 544x480, and 720x480) but they are not standards-compliant. 640x480 provides square pixels at 4:3, while 704x480 provides rectangular pixels at 4:3. There is no supported SD resolution that provides square pixels at 16:9; that would require something like 854x480. The only difference between 4:3 and 16:9 SD is a flag that tells the receiver whether it's 4:3 or 16:9. I've seen 16:9 flagged from 352x480 video before.

ATSC-defined HD video standards are 1280x720 and 1920x1080 only. If you want to show a 4:3 HD image (such as The Wizard of Oz, shot in 4:3 but an HD print derived from the original film) then you have to use black bars in the 16:9 frame to do so. Both formats provide square pixels.

- Trip
 

HoTat2

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Vertical resolution @ 720 lines, but horizonal can vary widely and sometimes the pixels are not square.
As Trip points out, for SD broadcast I certainly agree ...

But where have you ever seen an ATSC broadcast with less than 1280 horizontal pixels and still considered to be in HD?
 

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