480p, 720p, 720I, 1080I. (1 Viewer)

[Jeff_Standley]

Do all HDTV's display each one of these formats. I work in an electronics retailer and someone told me the other day that half of the TV's we carry wont do 480p, This seems very wrong to me. Our discussion was on xbox not going progressive on an HDTV. Help me to see the light once again, I thought I knew.

 

[MichaelFusick]

Almost all digital Tv's will display 480P.

If it's an HDTV or HDTV monitor then it does 480P. Analog tv's will not run progressive scan (480P), but only operate on interlaced scan (480i)

720P is the one that some sets don't do...

If the set does not do 720P, then it's probably not a good set, or a real HDTV. Sets that don't do 720P are usually budget sets with comprimised parts and engineering.

 

[Cooper_B]

I do not believe the above post is accurate about 720p. There are VERY few sets that do 720p because it requires more bandwidth than 1080i. So 1080i has become the more popular of the 2, both in broadcasts and TVs.

LCDs and Plasmas, though, should be more likely to support 720p or sometimes only 480p. All images on an LCD/plasma are progressive scan by nature, so it's easier to have 720 lines of resolution than 1080.

I do believe all HDTVs present 480p, BUT they may only accept 480i inputs, and then utilize their own line doubler. This is not good if you have a 480p source, like a progressive scan DVD player. Fortunately, I think most TVs take 480p inputs except for the low-end sets.

-Cooper

 

[MichaelFusick]

David Abrams explained some things very nicely about these issues. Below I copied and pasted one of his previous posts, he seems to have mastery level knowledge on the subject.

" Recently it has come to my attention that people do not quite understand what the majority of "HDTV" display devices are capable of. Most of them are not capable of handling 1080i correctly, they are only capable of doing 540p. Here is a brief explanation as to why this is so.

The 1080i system has 540 active lines in a 60th of a second and must accommodate 1920 elements in each line; even if the actual signal doesn't contain that much resolution. The 720p system has 720 active line in a 60th of a second with 1280 elements per line. The shorter retrace time in 1080i comes from the potential number of elements in the active picture area. In a 60th of a second it has to have an active picture of 1,036,800 elements (540 x 1920) where the 720p system has 921,600 elements (720 x
1280). There is more time for retrace in the 720p system because there are fewer active elements in a given unit of time.

Of course the real resolution of the 1080i system is about 1440 instead of 1920 even though the scan system must allow for 1920. The real resolution of 1080i is about 777K per 60th of a second. The 720p system can currently meet it's full potential of 921K and doesn't have interlaced artifacts.

The yoke assembly is an L/C tuned circuit. The difficulty of designing for the necessary bandwidth is logarithmic. The distance between 480i and 768p, (1367 x 768 for a 1.78 aspect ratio) in log terms is about 1.5 octaves. (The retrace time of 768p is about the same as 1080i.) The distance between 480p and 768p, which includes 1080i and 720p is about 0.5 octaves. The distance between 480i and 540p, which is what is being done in sets being upgraded from SD to "HD" is about 1 octave. If you start from scratch and design a yoke for 480p to 768p
there is only a half octave to be considered. It is easier to design and less expensive to build than the adaptation of an SD set to "HD". More important, it fits the requirements of true HD. SD is then upconverted to some progressive rate within the range of 480p to 768p. Good i to p converters are less expensive than the circuits required for the yoke, not to mention the improved picture quality of not dropping below 480p. Even at a half octave dynamic bandwidth, we switched the C values in the yoke circuit in the Princeton, depending on input frequency. That gave us even better control over the yoke.

As a calibrator it is easy to see that the set is not capable of 1080i by bringing the geometry in on the sides to the point where you can see the fold over of the picture. Basically, if you squeeze the picture down far enough you will notice that towards the end of the line the retrace starts and some of the picture information is drawn back on itself in order to get back to the other side of the screen to start the other line. If the yoke was actually capable of scanning the image properly it would be able to finish drawing the entire picture left to right, allowing for the full resolution of the signal to be utilized, and then going back to the other side.

Being that the necessary 48Khz scan rate for 1080i is higher than the 45Khz scan rate needed for 720p a set that can properly reproduce 1080i can easily reproduce 720p. Odds are that if you are looking at an HDTV set that does not have 720p capability it cannot properly reproduce 1080i.

Once again, if a CRT based set won't do 720p chances are it is not HDTV. If manufactures were to look at the specifications they would find that it is easier and less expensive to build a real HD set than trying to adapt an SD design.

Thank you,

David Abrams
ISF Calibrationist "

 

[Jeff_Standley]

Hey, Thanks alot guys. I thought he was wrong but figured I would check around.

 

[MichaelFusick]

Thought who was wrong?

 

[MichaelFusick]

Moderator or forum editor,

Should this post be moved to the Display deviced section and not the Widescreen review section?

 

[Mike Boeckeler]

Out of curiosity, do the Toshiba RPTV's like the 42hdx82, 50hdx82, 42h82 and 50h82 properly display 720p, or are they converting it to something else?

And what about some of the other RPTV's from different manufacturers?

Thanks,
Mike

 

[MichaelFusick]

They convert it to 540P/1080i

 

[Steve Schaffer]

From a strictly purist standpoint Mr. Abrams is most likely correct in saying a set that won't do 720p isn't "true HD".

There's another very widely held and also accurate from the purists standpoint opinion that any rptv with less than 9" crts (and there are damn few of them around) is also not "true HD".

The assumption that a set's inability to do of 720p natively is by itself indicative of low overall quality of parts and such is just plain silly.


There are many highly regarded "HD-capable" rptvs out there, including the Pioneer Elites, Mitsubishi, Hitachi and most Sonys that don't do 720p natively nor have 9" crts.

 

[Jeff_Standley]

Thought who was wrong?

A guy at my work. You know him?

 

[Michael TLV]

Greetings

Don't forget that some sets out there that do not do 720P consistently out perform some that do ...

So who is to say ... there is the theory and there is the real world ...

Trust your own eyes.

Regards

 

[Allan Jayne]

Also some HDTV sets and monitors display only 1080i in order to have just "one speed scanning" which simplifies geometry and convergence problems. 480p is still accepted. The incoming 480p is converted to 1080i (540p) which usually causes some artifacts.
This is what they probably meant by "not displaying 480p".
According to my calculations, 1080i is very similar to 480p in scan rate. 1080i and 540p are approx. sixty 565-1/2 line fields, or about 33,750 scan lines per second. (Not sure whether 540p frames have 566 or 565 scan lines) 480p is approx. sixty 525 line frames, or about 31,500 scan lines per second for a 1.07 to one ratio or about one tenth of an octave for 1080i vs. 480p. The 720p is approx. sixty 750 scan line frames per second for a 45 Khz scan rate. This makes me believe that it is more difficult to do 720p and avoid foldover and other horizontal scanning and retrace problems. The bandwidth of the yoke circuits needs to be much greater than 45 Khz to get the sawtooth waveform shaped correctly and get the first and last active (visible) pixels within the time the electron beam is moving smoothly and uniformly from left to right.
Good de-interlacing of 480i to become 480p gives a better looking picture as well as eliminate the need to scan at the slower 480i rate.
The set maker is forced to use more overscan to hide foldover or other imperfections at the ends of the scan lines.
Both 720p (1650 x 750 x 60) and 1080i (2200 x 1125 x 30) require about 37 Mhz video bandwidth to convey their full horizontal resolution. (one cycle stands for one dark plus one light pixel) But 720p shows degradation first if video bandwidth is insufficient, for example if the bandwidth is half the requirement, the 1080i can still reproduce almost 1000 distinct pixels all the way across while 720p then can't make pixels smaller than 1/640 the screen width. If it is displaying 1080i as opposed to 540p, even a cheap HDTV set can put a single dot in any one of the 1920 x 1080 possible active positions, not counting overscan, although three differing dots showing at the same time in adjacent pixel positions will be blurred together.
Video hints:
http://members.aol.com/ajaynejr/video.htm

 

[MichaelFusick]

Mosts sets won't do 1920X1080 anyways...

Even the Mits 73" 711 with 9" guns topped out at about 1550-1600 of the 1920 possible in this months Hometheatermagazine review