Hi,

I am new to HDTV so forgive me if this is a stupid/repetitive question. I have a Mitsubishi WS-55511 RPTV and it is not clear to me what it does with a 720p signal. Is it converted to 1080i or 480p? What resolution is a DVD displayed at using this television?

Thanks,

Jon

720P is upconverted to 1080I. DVD's are either 480I or 480P depending upon whether you have a progressive scan DVD player or not. Also, your TV will double to 960I for a 480I feed. You must set this up in your menu. You have a choice of 480P or 960I.

If your RPTV supports 720p input at all, it will upconvert it to 1080i. HD STBs do this also. If the TV doesn't support 720p input, you will get nothing with a 720p input - in that case use the HD STB to convert it to 1080i. DVDs are 480p if you use a progressive DVD player, otherwise its 480i.

Bobby,

I searched my manual for 960I and couldn't find anything. Do you have any other details or clues?

Thanks,

Jon

Mits TVs don't support 720p, just 480p and 1080i. Set the STB to output 1080i and it will scale the 720p down to 540p, which TVs think is 1080i.

Debunker,

I don't have a STB. My Mitsubishi has a built in OTA tuner. That's why I am wondering what happens to ABC's 720p transmissions.

Jon

> I searched my manual for 960I and couldn't find anything

That's because it isn't there. A 480i signal consists of alternating full-screen fields of 240 lines, with each field taking up 1/60th of a second. One is the odd numbered lines, the other is the even numbered lines, taking up 1/30th of a second. When a TV line doubles the 240 lines in each field, you wind up with 480 progressively scanned lines per field. These lines are exactly in the same positions as the lines in the next field when it is line-doubled. So you don't wind up with 960 interlaced lines per frame (two fields in an interlaced signal). You wind up with the same thing as 480p. That's what line doublers are said to result in.

1080i is two fields in 1/30th of a second. Each field is 540 progressively scanned lines in 1/60th of a second. This is the same as 540p (and why a TV can't tell the difference between 540p and 1080i), but the difference is that with 1080i the lines in alternating fields are offset (odd and even) so unlike above, you DO wind up with 1080 interlaced lines.

> My Mitsubishi has a built in OTA tuner. That's why I am wondering what happens to ABC's 720p transmissions.

The Mits tuner also scales them down to 540p. In a progressive signal, every 1/60th of a second is a complete frame. The tuner does NOT stagger them to create a 1/30th of a second frame that consists of two 1/60th of a second fields. Neither do STBs.

> The Mits tuner also scales them down to 540p.

So does this mean I loose the benifit of the 720P HD transmission? Sorry for being a bit clueless on this.

Jon

Technically, yes. But keep in mind this is a RPTV, which means the electron beams, which are overlapping (i.e. not distinct, same thing as blurring together) anyway on a 7" CRT, are also being blurred together by the fresnel and lenticular screens that make the TV viewable from more than just one "sweet spot." And depending on your viewing distance, the lines are probably being blurred together by your eyeballs as well. In other words, it's unlikely you'd see the difference on that TV.

Let me add something. If you have one of those 720p digital displays (i.e. 1280 X 768 LCD, etc), you'd get native 720p and would be able to see the distinct lines, especially if the LCD was part of a FPTV setup.

480p signals fed into it would be scaled up to 720p, and the 540 progressively scanned fields of 1080i would also be scaled up to 720p. Only the 720p source would be considered "high-fidelity" (highly faithful) in this case. The other two formats would display images on the 720p display with artificially created lines.

Your Mits has scan rates for 480 and 540 and will reproduce those without alteration. Other than ABC, this is the majority of of what you view, and that's what's important.

Let me clarify something about losing the advantange of 720p. Scaling lines doesn't change the horizontal resolution. So you still have 1280 points of data horizontally. Now whether your RPTV can display that is another story. Staunch RPTV advocates say that you can, while others believe it may be lower. It is certainly nowhere near the 1980 of 1080i.

With fixed pixel digital displays, horizontal resolution also has to be downsized, i.e. to make 1920 fit on a 1280 pixel wide LCD, or 1280 fit on a 480 X 854 plasma panel.

Finally, when we're talkin' 540p here, we're talkin' about scan rate. Although it isn't recognized by the ATSC, there IS a 540P X 960 format, just as there are many others not in the ATSC table, but allowed by FCC regulation.

>>But keep in mind this is a RPTV, which means the electron beams, which are overlapping (i.e. not distinct, same thing as blurring together) anyway on a 7" CRT, are also being blurred together by the fresnel and lenticular screens...

This is not the case with a properly calibrated display.

Richard F. Fisher
Mastertech Repair Corporation, Lawrenceville, GA
770-513-3987 E-Mail - help@mastertechtv.com
Have you been calibrated? ISF and HAA Certified
Factory Authorized
Mitsubishi, Hitachi, Toshiba, Harman Kardon, Infinity, JBL, NAD

Richard, you might be able to stop the overlap of 540p at the CRT by reducing beam spot size (at the expense of brightness unless you crank the beam up and burn the phosphors, but there's nothing you can do about the fresnel lens... or about the overlap at 1080i.

>>CRT by reducing beam spot size (at the expense of brightness

That is marketing talk. Beam spot size should be all about resolution. You achieve brightness by increasing light output which means larger projection tubes.

>> unless you crank the beam up and burn the phosphors,

If you were to do that then you would lose the beam spot size. Get bigger CRT's. and if 84" isn't large enough then get a stack, too expensive, or DLP, LCoS and DLP, not a CRT.

>> but there's nothing you can do about the fresnel lens...

The vertical is less sensitive to the screen dynamics than the horizontal.

>> or about the overlap at 1080i.

If the beam spot is small enough and the screen large enough you can see it. Easily seen on any Mits 73" prior to calibration and visible on most 65"s after calibration.

HDTV RPTV's have come a long way. I am thrilled to own a display that I could get to work correctly. All displays have their individual issues and many factors must be taken into account. If these things are important than one should get with their local ISF calibrator/dealer for product selection.


Richard F. Fisher
Mastertech Repair Corporation, Lawrenceville, GA
770-513-3987 E-Mail - help@mastertechtv.com
Have you been calibrated? ISF and HAA Certified
Factory Authorized
Mitsubishi, Hitachi, Toshiba, Harman Kardon, Infinity, JBL, NAD

I don't think 9" CRTs are an option for Jon. And only being available in the 73", they aren't an option for most folks.

You don't need 9" CRT's as much as you need to use the correct application. In this case a darkened room will reduce the need for contrast and brightness allowing you to operate the display within it's useable beam current/focus range.

Richard F. Fisher
Mastertech Repair Corporation, Lawrenceville, GA
770-513-3987 E-Mail - help@mastertechtv.com
Have you been calibrated? ISF and HAA Certified
Factory Authorized
Mitsubishi, Hitachi, Toshiba, Harman Kardon, Infinity, JBL, NAD