DVD material on standard RPTV vs. HD RPTV (1 Viewer)

[Mike I]

Most HD sets do not display 480p as 960i...Some do while others give the option..If given an option the native 480p would be the way to go to reduce artifacts..

 

[Jeffrey R]

The Sonys always scan at 1080i, 480i and 480p get converted to 960i, which is inserted into the middle of the 1080 lines by the MID circuitry leaving 120 unused lines. Vertical size is then increased to move the lines with no video information into the overscan area. This method allows for one scan rate and keeps the conversion simple. 480i is line-doubled by DRC, 480p bypasses DRC and is simply converted to 960i by the MID circuitry.

Warner, can you please elaborate on what you are saying here in this quote. I was the one who corrected you back in this thread when you said that Sony's DRC converts 480p to 960i. But, now you've taken it a step further and I'm still confused about what you are talking about. You now correctly state that Sony's DRC is bypassed with a 480p signal, but you now say that this 480p signal is converted to 960i by some other process in the television? Is this common knowledge? I have never heard that the Sony HDTV's convert 480p to 960i, at any stage. This would seem inconsistent with the fact that you can convert a 480i interlaced DVD signal to 960i, 480p and 480p with 3:2 pulldown using Sony's DRC. By what you are saying, you can convert an interlaced signal to progressive, but you can't watch a progressive signal as progressive. This doesn't seem to make sense. Anyone else know if what he is saying is true? Thanks.

 

[Todd Hochard]

Think of the implications if you believe that an HD set displays 1080i as 1080i, yet displays 480p as 480p or 540p. OK, 540p and 1080i would have the same scan rate, but with 540p the set must double the size of each scan line compared to 1080i in order to fill the screen with no gaps, and that just does not happen. The reason you can't see scan lines as easily on an HD set is because there are more scan lines and hence they are smaller.

But interlacing isn't just about scan lines. There are artifacts, visible even at 1080i, that make interlacing a less desirable option.
My Pioneer Elite 510HD displays 480p as 480p, and 1080i as 1080i. Scan rate is 31.5Khz for 480p, and 33.75Khz for 1080i. I can see very small gaps in the scan lines at 480p, but only within 5 feet from the screen. At 1080i, many of the scan lines overlap, due to limitations in beam size (i.e. it can't be made small enough) with 7" tubes (commonly used in most HD RPTVs). The overlap on my set begins around 600 lines.
Given the choice between 480p and 960i, I choose 480p. I prefer the image to be as unprocessed as possible.

Todd

 

[Warner]

I'm going to paste a few posts made on another HT forum that explains how Sony HD sets handle and display various signals. I would provide a link to the thread but I'm not sure of the rules around here. I figure it's OK to copy and paste the post as long as I give credit to the author. I'm pretty sure no one copyrights posts made on a forum. The author trains Sony technicians and on occasion has personally stepped in to help forum members get their set properly serviced by Sony. That should verify his position, and he posts under the name "Sony Expert". Here it goes...

Post 1 by Sony Expert.

"OK. Let’s try and settle this subject.

ALL 480i resolutions pass through the Digital Reality Creator (DRC). Its purpose is to double vertical and horizontal resolution in order to create a “near” HDTV picture by doubling the scan lines to 960i. The greatest advantage to this feature is the elimination of visual scan lines which is of great benefit on larger television screens. However, the simple concept of double scan lines is not so simple. This was attempted over 10 years ago in some televisions with poor results. That was before digital processing and computing power were at the stage they are today. Our biggest problem to overcome when doubling the scan lines is time.

We all know that interlace scanning involves generating one-half the video information on one sweep of the TV screen by scanning the odd numbered lines and scanning the next half on the even numbered lines. This works rather well since the human eye will blend these into one picture frame with minimum flicker. The main reason for attempting to double these scan lines is not so much to increase resolution, but to minimize the scan line visibility as the screen size increases. Sounds simple, doesn’t it?

The problem we have here is that the source material is interlaced. Each field of information contains half of the total information. If I try to double the information of one field, I am simply repeating the same information to produce 2 lines and then doubling the other half of the other half of the information. Confused? Don’t blame you.

Imagine a white raster with a vertical line, which starts at the lower left corner of the screen and progresses diagonally to the upper right corner. In interlace scanning, half of the information would be scanned, and then the other. The eye would blend the line to produce a true, straight, diagonal line (Assuming it was a stationary line). If I attempt to double the scan lines, I would be generating twice the information from half the source. This would create extra scan lines that are repeating the same information. The result would be jagged edges from repeating the same information twice. Those of you who are into computer graphics programs would know this as “aliasing”.

The DRC is loaded with thousands of pattern recognition algorithms that have been loaded from HDTV broadcasts. It is able to determine what should be on the next line based on this. Not only is it able to determine what the next scan line should be; it is also able to calculate the next pixel based on a higher scan rate. This is how it can double the horizontal, as well as the vertical, resolution.

How well does this work? It depends on the signal quality received. Any ghosting, or snow in the broadcast, are going to confuse the DRC. Small characters such as movie credits are a perfect example. If there are ghosts on the letters, the DRC will have a problem. Low signal strength with snow will also drive it nuts. DVD quality video produces the best results. If it sees “garbage”, it will try to make a better garbage based on its stored images. Let’s look at the 3 options you have with DRC.

Progressive: This is used for still pictures only. Since a still picture of 480i consists of a repeat of the A and B field, the DRC has no interpolation to do. Set it to this mode for viewing of photographs or graphics.

Interlaced: Use this for any video whose source is NTSC video such as soap operas, news and documentaries.

Cinemotion: Any source material that was originally shot with film. The 3:2 pull-down. that was done with the tele-cine to convert the material for television broadcast will confuse the DRC since it sees 3 repeat frames and then 2 repeat frames, which doesn’t jive with the programming. The Cinemotion will recognize the 3:2 pull-down and ignore it and process the procedure in the pre-programmed digital circuitry..

480P: Since twice the information is being transmitted in the same time as 480i, the signal is sent directly to the Multi-Image-Drive circuitry, which converts the image to 960i. The DRC is not necessary, since twice the data is present and the only purpose here is to double the scan lines to increase picture clarity without the need of the DRC circuitry.

Post 2 by SE in response to questions.
1. Do I understand you to say that a 480p signal is converted to 960i? What's the purpose of doing that and do other HDTV's do this?

Imagine seeing 480 scan lines on a 65” set. They would stick out like a sore thumb

2. Please elaborate more on why Interlaced is preferable for NTSC video sources. How does it handle the moving images better than Progressive and why should film based material be converted from 480i to 480p instead of 960i as with video material?

The progessive mode only displays one field of video to eliminate the flicker between A and B fields from the source. Very much the same way a 3 or 4 head VCR will switch its heads so as to scan the same track (field) twice while in the pause mode. If you view interlaced NTSC video in the progressive mode, you are only going to see half of the video information since the same field is being scanned twice.

3. What changes were made in DRC from last year's models?

The addition of Cinemotion to remove the 3:2 pulldown

4. Do other HDTV's line doublers work essentially the same way or are their fundamental differences?

They all use some kind of interpolation circuitry to minimize jagged edges. The more elaborate, the better they accomplish this although they cannot do it perfectly. DTV was designed to eliminate this problem once and for all.

Post 3 by SE.
All signals except 1080i are processed by the Multi-Image Driver. The set always scans in the 1080i mode (33.75KHZ scan grequency) so its right on over to the RGB encoder and to the CRT drivers. 1080i does still go to the MID but only for mixing sub video for twin picuture viewing.

Here's an example: 480i signal source (15.75KHZ scan). DRC doubles scan lines. Signal is now 960i (31.5 KHZ scan). This must be inserted into the 1080i lines. The MID does this by placing the 960i right in the middle which leaves 120 unused lines (60 above and below). Vertical size is increased to move the lines with no video information in the over-scan area.

End of posts by Sony Expert.

So I'm sure as heck that Sony HD sets display everything as interlaced. It's my opinion that other brands also do so, or else the 480 scan lines "would stick out like a sore thumb" on 65" set.

 

[John Royster]

As an aside Mitsubishis display 480i as 480p, you can also select in the menu to display at 960i. User selectable, I like that on my 65819. I use 480p and 960i for different kinds of 480i material.

480p is displayed natively as 480p, thank god.

540p, 720p, 1080i are shown at 1080i. So the TV has two scan rates, two sets of convergence/geometry.

Different TVs behave differently thats for sure.

 

[Jeff Rogers]

I have a question...

Since I am still new to this.. Ragarding Mitsubihi tv's

I have the 46809..When watching a movie off a non progressive dvd player...does it automatically double the lines? Or do I have to go to the menu and select 960i ??

Have I been missing out?

Wwen I get a progressive next week (in time for LOTR) do I have to change it back to 480i on the menu of the tv? Or will it automatically disengage the doubler?

 

[Jeffrey R]

Warner, thanks for the follow-up, but I got to tell you the truth, I'm still skeptical that Sony HDTV's convert all 480p signals to 960i with the Multi-image drive circuitry. Any reference to "Multi-image drive circuitry" that I can find in Sony literature (on the web or elsewhere) talks about it in the context of Sony's picture in picture mode, which would make sense based on the name "Multi-image...". Apparently, when you use Sony's PIP, it performs some conversion of the signal using the multi-image drive circuitry. I am still not so sure that the Sony HDTVs convert a 480p signal, from a progressive scan DVD player, to 960i for regular non-PIP viewing. Just my .02 cents.

 

[John Royster]

Jeff,

when receiving interlaced video you can select 480p or 960i via the menu. when receiving 480p video the line doubler is indeed bypassed and not used, the settings have no affect. have fun with your new progressive player, it'll blow you away.

-edit- this was for Jeff Rogers, RE: Mits

 

[Warner]

480p is displayed natively as 480p, thank god.

I thank God Sony displays 480p as 960i. Progressive scan sucks at the display of moving images. Yup, movies are moving images. I'm also grateful that Sony is not a big, fat red-pushing pig.

 

[John Royster]

LOL,

The only time I had red push was the first week I had the set. Anyway, off topic now since I've got ruler flat greyscale, color decoder, zero edge enhancement and the whole works.

Brian,
Have we answered your questions or just do more to confuse you?

 

[Jan Strnad]

Progressive scan sucks at the display of moving images.

I'm intrigued, since this statement runs counter to everything I've read about interlaced and progressive scanning.

Would you care to elaborate?

Jan

 

[Jeff Rogers]

To ask for a little clarification..

I understand that the prog. scan will bypass the line doubler.

I understand that I have to select 960i from the main menu to activate the line doubler, since I don't have the prog. right now. Right?

If that is the case..then what is the "film" and "video" mode for? I thought that is what activated the line doubler.

Again..any info is much appreciated. :b

 

[John Royster]

Jeff Rogers, on Mitsubishi HDTVs...

with a 480i source the TV will "double" the scan lines to either 480p or 960i, selectable in the menu. The global Film/Video mode selects 3:2 pull-down. Basically use video for 30 frames a second material and Film for film's 24 frames a second. These two settings (480p/960i) and video/film control your line doubler

So when fed a 480p signal both of these settings are useless and not applicable.

I use 960i/video for sports, TV. 480p/film for movies and other 24 frame shows on TV. I have a progressive scan DVD player so for DVDs it is a mute point.

Try the different settings out on one of your favorite DVDs (you'll need the film setting here, but play around and learn to notice the uneven movement/panning difference between video and film)

Good luck! hope this helps.

 

[Jeff Rogers]

Indeed. thanks!

 

[Warner]

OK, I’ll try to stay on topic. Brian’s question - Why do DVDs look better on an HD set, even when using an interlaced player? What happened to the scan lines?
Movies are stored on DVD in interlaced format, 480i. Conventional analogue TVs also display images in an interlaced format, 480i. If no conversion whatsoever was best, one might think that the best way to display DVD is the native format, with an interlaced player and on an interlaced display. Obviously this is not the case, why do they look better on HD sets?
480i means that even though each complete frame of the movie consists of 480 lines of information, your set displays the frame as two separate “fields” of information. If the lines were numbered sequentially, on the first pass of the screen it draws the 240 odd numbered lines, and then on the second pass of the screen it draws the 240 even numbered lines. The even and odd numbered lines are drawn in separate passes and “interlaced” with each other. This happens too fast for your eyes to see, each pass of the screen is completed in 1/60 second, but since it takes 2 passes to draw both fields, it takes 1/30 second to display one complete frame. Our eyes see the two interlaced fields as one image, and as mentioned by Allan it was done this way because if the lines were drawn sequentially, or “progressively”, by the time the lines at the top were drawn, the lines at the bottom would be fading, resulting in flicker. So, an interlaced player must send the tv one field of information every 1/60 second, resulting in one frame every 1/30 second, to match the pace of a tv displaying 480i, and it does! OK so far?
If your player is progressive it essentially outputs one frame, all 480 lines, every 1/60 second. An HDTV displaying 480p draws all 480 lines in one pass of the screen every 1/60 second. Double the speed of an interlaced display, and now we don’t have to worry about the bottom of the screen fading while the top is scanned! But wait! At this rate the movie will be finished in only half the normal time! Not good! For arguments sake, let’s say the best work-around for this is to have your HDTV display every frame twice. It seems to be the consensus here that this is why the scan lines are less visible, they are being retraced progressively every 1/60 second instead of every 1/30 second and your eyes no longer see fading odd numbered lines between the freshly drawn even numbered lines. If a line is retraced every 1/30 second, let’s assume that half the time it is fading and half the time it is brightening. If you can see a line fading for 1/60 second, you should also be able to see it brighten for 1/60 second. In one second you should see it dim and brighten 30 times! At any given moment is line number 212 dimming or brightening? How about line 213? Is it dimming or brightening? If anything, you might see both lines 212 and 213 flicker, but I don’t think so because then you would see all lines flickering, the whole screen.
Nobody asked why analogue sets flicker and HD sets don’t. Scan line visibility is the difference often mentioned. If retracing scan lines at twice the speed is the answer, those of you who don’t see scan lines on your HD set while watching 480p, must see scan lines when watching 1080i, because 1080i only retraces the scan lines every 1/30 second, just like 480i. Is that the case?
Sorry, I’m off track, Brian asked about interlaced players on HD sets. Interlaced players send an HDTV only 240 lines or one field of information every 1/60 of a second, or only half the picture. An HD set must “guess” what is on the missing 240 lines in order draw all 480 lines in one pass. It has not received the other 240 lines from your interlaced player yet. When the other 240 lines do arrive, the tv must again guess what belongs in the missing lines. Line doublers do the “guessing”, but they use interpolation and algorithms to predict the missing part of the picture based on the information it does have, and given a good clean signal like dvd can do a pretty good job. The Sony DRC progressive mode will assume a 480i signal is of a static/still image and do no interpolation when line doubling since a still image is simply a repeat of the A and B fields. If you use it for film or video sources you may notice “jaggies”. Use Cinemotion mode for all film based material, and interlaced for video.

 

[Brian Dobbs]

Have we answered your questions or just do more to confuse you?

I understand all of the topics discussed so far, but I'm confused as to why there still isn't a consensus about the subject. I am still confused as to HOW a 480p signal (from a PS DVD player) is displayed on a HDTV. Does it display 480 lines of resolution, like a standard TV, or does it display 480 lines of resolution within 1080 lines, sort of like how the 960i resolution works? I don't want to sound like I don't believe anyone here, but is it a fact that an interlaced signal is the only reason why i can see the scan lines? I am just still wondering why progressive scanning makes the lines less apparent.

I have a couple of other questions. How does a HDTV derive 960i from 480i? Also, where does a 540p signal come from?

 

[Warner]

Sorry Brian, I'm probably the one guilty of causing the confusion. I think everyone would agree that simply put, HD sets display twice the number of lines in the same amount of time, so it's harder to see the lines.
Toshiba and Hitachi

 

[Brent Hutto]

I had posted a new topic before finding this one. Sorry for the duplication but it seems my questions are being discussed here...

I just bought a Hitachi 36UDX10S at Circuit City -- hasn't been delivered yet. Today I've found out that when I play an anamorphic DVD on that monitor, the 480i signal from my player will be upconverted to 540p, displayed as 1080i except when I ask the player to do the "squeeze" it will turn around and throw away every fourth line. Doesn't sound like the best way to get a sharp image on a 'scope movie.

That's all if I set the DVD player to 16:9 mode. If I leave it set to 4:3 mode, the player will throw away every fourth line ahead of time and the resulting 480i (with black letterbox bars wasting space) will be upconverted to 540p and displayed as 1080i. Do I have all this right?

If so, why would I bother to set the player to 16:9 mode? Can the upconvert process work better with the full (anamorphic) information, even though it is going to throw 1/4 of it away at the end?

I have a feeling I'll be using the Hitachi for a while and then asking Circuit City to swap it for a Sony 36HS500 when they become available. Should I even waste my time with the Hitachi?