Toshiba 540p 65H81 vs 720p 65H82?

[dlaraman]

Would like to ask about my Toshiba 65H81 set, which I am told supports 540p vs the newer 65H82 set, that supposedly supports 720p. Speculate that I can't get true HDTV resolution using the Toshiba 540p PScan player coupled w/ my rear projection TV based upon the specs he listed regarding scan line and pixel resolution per minute, but want to confirm this to be true. Guess I should have waited for the 720p set, but even then wouldn't I have needed a 720p DVD player to fully exploit the set's capabilities? Guess I don't have complete or accurate understanding of how all this works and the difference between 1080i HDTV signal vs 540p/720p DVD signal. Hopefully I didn't make a bad investment since it cost me about 3k.


*Found the following information out on

http://www.audiovideoforum.com/forum...p?s=&forumid=2

from generic Google.com search that I reviewed and it was helpful, but would still like further clarrification in laymans terms as to what my SD-3800 540p DVD player and 65H81 HDTV can do optimally concerning supporting HDTV interlace and DVD progressive signals and how they all integrate. I will search the dvdfile forums as well for additional insight.


Is it Really HDTV?
Dear Forum Members,

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
Precision Theater Consultants
I2C Equipped


__________________
David Abrams
ISF Calibrationist
Precision Theater Consultants


Scaling Technologies
The question of scaling technologies and display devices has come up to me many times. Often people confuse what scaling is and why it is used. First let’s explain what scaling is. Scaling is taking the video signal and converting it to a different resolution in order to better fit a display device. For instance, a progressive scan DVD player has a scalar in it known as a doubler. A doubler takes a video signals interlaced images, the odd lines and even lines of the picture, and de-interlaces them into one full frame. By doing this it is “doubling” the amount of information that is one the screen. There are now twice as many lines in the signal and twice the amount of information. A doubler allows for the most resolution available from an interlaced NTSC source. Once the image is de-interlaced you have successful extracted the maximum amount of resolution capable from the source. With a DVD this is about 720x486.

Now there are other scalars that are used to up-convert signals to even higher resolutions, but these only play a trick on the eye. Real or “actual” resolution is measured by the amount of detail in the picture. The amount of detail is limited to the format and on what camera it was shot. If the program was shot on 35mm film then the potential resolution is around 4,000x3,000 whereas if it was shot in HD the potential resolution is 1920x1080. This is the amount of detail that is in the picture. However, there is also “perceived” resolution. This is what the human eye can see. By taking a DVD and up-converting it to 720p via a Faroudja or Runco scalar you are not creating any more detail, but splitting the information to accommodate a higher scan rate. By doing this each line becomes smaller and eye perceives this as a higher resolution. In actuality a small resolution hit is taken during the up-converting process.

Using a scalar on a CRT device is often necessary to utilize the CRTs full capability. By using the optimal scan rate on the device you are maximizing your light output as well as hiding the scan lines so that the picture appears more film-like. However, CRT devices can often display a signal in it’s native format and that allows for signals to go unprocessed allowing for signal to be viewed either way.

With an LCD, DLP, or Plasma type display device scalars are used in order to map the picture to the native resolution of the device. Say you have a DLP with a resolution of 1024x768, you would not want to run this at 720x486 because you wouldn’t be using all of the pixels on the projector and there would be a huge loss of resolution because the device is designed to work off of the entire chip. With a plasma display it also comes down to the pixel array of the panel, you need to use the panel at the resolution that it is in order to have it work more efficiently. With these devices sometimes the internal scalar is insufficient and can cause a terrible picture.

Either way a scalar is important. You do not need a scalar with a CRT display device but it is often a good idea if the CRT is capable of running at a higher resolution. With an LCD, DLP, or Plasma device there is always a scalar included but sometimes they are poor and you will need to acquire an external scalar to compensate for the shortcomings of the internal one. Always take into account the scalar or the lack thereof when purchasing any kind of display. With today’s technologies scaling is often inevitable.


__________________
David Abrams
ISF Calibrationist
Precision Theater Consultants

[tomdkat]

Originally posted by dlaraman
Would like to ask about my Toshiba 65H81 set, which I am told supports 540p vs the newer 65H82 set, that supposedly supports 720p. Speculate that I can't get true HDTV resolution using the Toshiba 540p PScan player coupled w/ my rear projection TV based upon the specs he listed regarding scan line and pixel resolution per minute, but want to confirm this to be true.

First, thanks for posting that. Great reading material. Threre's yet ANOTHER research project to undertake...

As for getting "HD" video quality from your DVD player/HDTV (well, "supposed" HDTV... ), I'm not sure it was ever indicated that one _could_ achieve "HD" quality from a DVD source.

Hmmmm..... now I'm getting MORE confused than I normally am!

Here is a related thread on AVS Forum.....

Peace.....

[dlaraman]

Also emailed Toshiba's techs at customer_support@tacp.com w/ following short inquiry and affiliated links to find out more:

Hello support staff,

I have a Toshiba 65H81 Widescreen HDTV and an SD3800 540p Pscan DVD player. I thought they were a good match initially both being 540p compliant but want to be sure the 540p signal supposedly outputed by the dvd player is natively played or directed to the guns on the TV w/ any kinda of analogue to digital conversion. I am also a bit confused about 540p vs 720p because apparently 720p is much better suited than 480i,480p,540p,& 1080i for HDTV in accordance w/ the forum research I've partially listed below regarding interlaced artifacts given the number of active lines and elements per 60th of a second w/ respect to retrace time . This is most probably why the newer 65H82 features 740p w/out conversion or so I've heard. What is your expert opinion on this matter involving optimal TV and Video resolutions for best picture quality and the component compatability based upon the units I've already purchased???

Sincerely,
David Laraman
IBM Software Engineer

http://www.dvdfile.com/interactive/f...threadid=26232

http://www.plasmatvs.com/hdtvvsanalogtv.html

http://www2.leitch.com/agile/dtv%20t...20standard.ppt

http://www.avsforum.com/avs-vb/showt...0&pagenumber=1

[Mr Bob]

I have not had time to completely read and adequately digest what David has written above, but hopefully one question can get answered, that did come up when I read the first part of it. (And then found in his next entry - on scaling, a must-read, of course - that some MORE intense continuation of such reading was going to be in order, as soon as I find the time...this is not stuff I breeze thru easily...)

That is, 1080i is either 31K or 33K, depending on whether you are using the component or the RGB inputs, RGB being 33K.

If that is the case, doesn't 48K refer to 1080p, rather than 1080i? I have never heard 1080i's electronics refered to as 48K. Only as 33K, tops.

At CES in January, when Panasonic was explaining to me why they are not doing 720p anymore, they refered to the 33K used by 1080i, and said that it is much more expensive to do circuitry capable of 720p -> 45KHZ - than it is to use circuitry capable of 1080i -> 33KHz. And that they were not choosing to produce the much more expensive 720p/45KHz-capable circuitry anymore, with the continuous downturn in RPTV prices that is going on right now, and has been for quite some time.


???

Mr Bob

[Mr Bob]

Just thought of something else.

Is the unit in question capable of displaying 720p NATIVE?

You can find MANY RPTVs labeled, "720p capable". That means that your TV is capable of receiving 720p and displaying HD. In the case of Toshiba - and everyone else - that means 1080i. They take the 720p and downconvert it to 1080i. Therefore it IS "720p capable".

That is NOT the same as "720p Native-capable". I don't know of any CRT based RPTV presently being produced that is capable of displaying 720p native like the 2.5 year old one I have - the Panny mentioned above, produced in year 2000.

I certainly HOPE that changes!


Mr Bob

[Mr Bob]

I just read the first page of the link Tom had above, and responded, over there at AVS.

Here's what I said, FWIW:

I believe both LCD and plasma - and of course DLP - I believe that all the fixed pixel displays currently out there have 720 as their fixed vertical lineup these days. Not just plasma or DLP. How they do 1080i is actually a mystery to me, tho I'm sure they just delete the proper number of lines, to leave 720 of the 1080 visible.

In the SF Bay Area, Fox broadcasts in 720p, obviously upconverted from 480p, but very well done. I watch 24 in it every week, and tho Ally McBeal was very underwhelming, 24 looks awesome. Every so often you can see the compression squiggling on some static background scene in it, but for the most part, you'd never know it started out as 480p. Whatevery upconverter they are using is WAY up there in studio quality.

How do I know it is 720p? My Panasonic STB, one of the earliest issue, with the DVHS firewired along for recording HD - has a Recall button, that tells you EXACTLY what is coming in OTA, on whatever channel you are on. It will even tell me when it is 480i coming in.

And my Panny from year 2000 does 720p native.

They don't do that anymore, unfortunately.

I asked Panny why at CES this year, and they told me that it is much more expensive to produce 45KHz electronics - 720p - than 33K (max) electronics - 1080i. It is a cost/return issue and they have decided that with the prices of RPTV having come down so much in recent years, it is no longer economically feasible to be producing electronics capable of 45KHz anymore on CRT based units.

They did 2 interspersing runs of 720p native-capable sets, and mine - the year 2000 model - was the last one. They don't have any plans to be going into production again, of those higher-freq capable electronics.


Mr Bob

[tomdkat]

Originally posted by Mr Bob
In the case of Toshiba - and everyone else - that means 1080i. They take the 720p and downconvert it to 1080i.

What do you mean by "downconvert" of the resolution is going from 720 to 1080? Or does the "upconvert/downconvert" terminology apply to whether progressive vs interlaced video is being discussed?

Peace....

[Mr Bob]

My info is that 720p to 1080i is a downconversion, not an upconversion. Yes, 1080 is a higher number than 720. And 720p to 1080p would definitely be an UPconversion.

But 720p to 1080i is a downconversion. Probably because essentially 1080i = 540p, in the numbers that actually count, which I believe in this case would be the actual number of DIFFERENT lines of info. 1080i still only contains 540 DIFFERENT lines of info.

Please correct me if any of this is wrong. I don't THINK they use line synthesizers to come up with the remaining 540 lines, to make up 1080i with. I believe the second set of 540 lines is ID to the first set, just interlaced with it. But I am willing to be corrected on this.

Mr Bob

[tomdkat]

Originally posted by Mr Bob
But 720p to 1080i is a downconversion. Probably because essentially 1080i = 540p, in the numbers that actually count, which I believe in this case would be the actual number of DIFFERENT lines of info. 1080i still only contains 540 DIFFERENT lines of info.

Wow.... in that case "HD" really isn't "all that", or is that not really a "fair" statement?

Peace....

[Mr Bob]

Oh, I wouldn't say that.

1080i still has over a thousand horizontal lines visible, vs. 480 for DVD.

I still can't see scanlines in either format, 1080i or 720p, except in very specific types of scenes, which are very few and far between. The motion artifacts inherent in ANY interlaced format are simply not there in progressive, which makes my vote go to 720p every time.

In 480 - i or p - I have absolutely no trouble seeing scanlines on a properly calibrated set even on stillframe - with or without motion artifacts. This can be very distracting.

I definitely think HD is "all that". I LOVE IT!



Mr Bob