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TV Video questions


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#1 of 12 OFFLINE   Wayde_R

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Posted April 13 2004 - 09:28 AM

Hello. Sorry about all newb questioning in the forum today. Please correct me if I'm wrong in any assumption I make about video and TV. Regular (non-hi def) broadcast TV has 480i. 480 lines horizontal interlaced. Do they give a number for vertical lines? I understand interlaced means every other scan line alternates on/off position each cycle. But what is a cycle? Do the scan lines alternate their on/off cycles with each frame? I believe NTSC video has 25 frames per second (is this correct?). So, that means 480i alternates 25 times per second. Or is there some other frequency by which interlaced video signals are alternating. The best a DVD player can do today with progressive scan is upconvert that 480i image to 480P on a TV capable of such definition. I've read people talk about upconversion to 1080i, how can this be in our pre-HDDVD era? Don't they really mean it's upconverted to 480P on an HDTV capable of 1080i? Thanks in advance for answers to some of these questions. I've read the newbies guides here on this site and on others, very helpful. Wayde
Happy Halloween!

Wayde Robson

#2 of 12 OFFLINE   ChrisWiggles

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Posted April 13 2004 - 11:42 AM

ntsc is about 30 fps, with a refresh of 2x that of 60 fields per second. exact numbers are just slightly less than that, 29.97 frames and 59.94 fields per second. video processing can scale video to pretty much whatever, and there are now players, like the momitsu v880 that can scale things to higher resultions like 720p or 1080i. This is what HTPCs and high-end video processors are used for, for more quality processing/scaling.

#3 of 12 OFFLINE   nick_rh

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Posted April 13 2004 - 11:52 AM

No, it really is upconverted to 720p or 1080i. That doesn't change the quality of the original image; it just scales it up so it matches the native resolution of the display. It's the same principle as taking an 8mm filmstrip and blowing it up to 35mm. The quality of the film is still exactly what it was on 8mm, but the blowup makes it suitable for showing in a 35mm theater.

#4 of 12 OFFLINE   ChrisWiggles

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Posted April 13 2004 - 11:57 AM

nick: the quality of the video is very very much improved when scaled properly for a display. I think you mean, though, that detail is not added, which it cannot be. However, with good processing, the image is drastically improved for a high-resolution display, especially of a large size. IT is not quite akin to blowing up film, but like blowing up film, you can't *create* detail that wasn't there. That's why DVD scaled up to, say 720p, will not be as high quality or as sharp as the 720p master of the same from a high-def source. However, new picture information is attempted to be created, in essence by the video processing, to increase the resolution. Your analogy is not quite right, and a little misleading. It is not just blowing up the picture, or leaving the picture data exactly as it is. Lots of new picture data is being added, but the weakness here, is you can only do so much with what you are given, in estimating what *would* have been in the picture originially with a higher resolution source.

#5 of 12 OFFLINE   Wayde_R

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Posted April 13 2004 - 10:55 PM

Thanks, this is good information. My questions about cycles and frames per sec was answered. I now understand that when claims of upscaling to HD resolutions by VCRs is really a matter of scaling it to fit the higher resolution without adding details. I agree that they look pretty good, I've seen video upscaled like this but I thought I was just looking at 480P. It's a bit "iffy" on derriving a high res image from a regular DVD. I'm positive it looks great but when the HDDVD comes out I'm sure we ain't seen nothing yet.
Happy Halloween!

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#6 of 12 OFFLINE   Wayde_R

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Posted April 14 2004 - 12:01 AM

One more question about TV video. Regarding this upscaling of video from DVD players to HDTVs. As I understand this will require at the very least the use of Component output cabling, correct? This is where the video cables are separate for R,G,B and Horizontal and Vertical sync. So, five separate cables for real component outputs and you can get this upscaling. It wouldn't be possible using a composite or s-video connector, right? Of course the digital delivery methods like DVI and HDMI are fully capable of delivering the full line of progressive scanned signals. Thanks again guys or gals. Wayde
Happy Halloween!

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#7 of 12 OFFLINE   ChrisWiggles

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Posted April 14 2004 - 04:32 AM


You are on teh right track, but component video is not the same as RGB. They both, however, are capable of transmitting full high-def signals. RGB, as you noted, is usually used as 5 different wires, for R,G,B and horizontal and vertical sync. Component video puts a variation of this through 3 wires, and is common on most consumer equipment like DVD players. RGB is prevalent in the professional and high-end world, and via the computer outputs. The VGA connection to your computer monitor almost certainly is using RGBhv. RGB can also be transmitted via 4 or 3 wires as RGBs, and RGsB, but it is still different from component video. You can run a search on google and you'll get some good info, here is a good site that i dug up fast, i recall some others that explain it a little less technically if you wanna hunt around a bit.

http://www.syncblaster.com/gtmfytv.htm

#8 of 12 OFFLINE   Matthew Todd

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Posted April 14 2004 - 05:37 AM

You can take a composite or s-video feed and upscale it to a higher resolution, but if you have a choice (if you're using a DVD player, you almost certainly have a choice), you don't want to do it this way. You'd rather use component or RGB. For example, if you are using an HTPC or a scaler, you can plug a laserdisc player into it (you will either use a composite or s-video cable) and you can get an upscaled picture out. Matt
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#9 of 12 OFFLINE   Wayde_R

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Posted April 14 2004 - 08:17 AM

thanks for the great info. Thanks for the link Chris I navigated to other links from it to read about deinterlacers and scalers. It brings up a few more questions. A few terms being bandied about I am a little unclear on and not sure if I need these features. DTV (digital TV) I understand is a catch term for HDTV, anything capable of 480P or greater. There is also something called a DTV tuner out there that you can buy separate or have included in your HDTV. This DTV tuner performs the job of upscaler (and maybe deinterlacer depending on the model?), correct? Is the absence of a DTV tuner what they call an HD-ready set? And is an HDTV-ready set still considered a Digital TV (just lacking a tuner)? Some DTV tuners lack 2:3 pulldown processing (my first impulse is to think that's cheesey). Is 2:3 pulldown processing mainly just for DVD players since 2:3 pulldown is mainly for upping films framerates and maybe wouldn't be required for watching a hockey game on old fashioned CBC? If I'm watching TV from an HDTV capable satellite dish receiver, that receiver is serving as my DTV tuner (correct?). This means that non-HD broadcasts are being upsampled to higher res and will look roughly as good as a DVD played through component outputs (so an HD sat receiver probably has component outs or digital DVI or something). Correct? If I'm using a regular old style satellite receiver with no HDTV capabilities and only a simple S-video output, my set should have a DTV tuner to upscale this to better resolutions, is this correct? If I use a regular old Satellite receiver or cable box with only S-video or composite video and have no DTV tuner built into my HDTV I'm getting the worst possible picture from the TV. Is this correct? And can I improve upon that picture by either A/ buying an HDTV with a built in DTV tuner or B/ buying an HD capable satellite receiver. I'm a bit torn here. I won't go out and buy an HDTV sat receiver just for the HD content right now, there just isn't enough out there. But I've seen what S-video satellite programming looks like spread across a 50" HDTV with no DTV tuner and it aint pretty (I'll just stick with my 32" analogue TV thanks). But if I can get a picture approaching what a DVD player with progressive scan gives to that 50" HDTV from a regular old satellite receiver, count me in. I'd even consider that 50" HDTV if an HDTV satellite receiver can upsample non HD broadcasts. This is a long one, but I think I'm starting to "get it". Thank you for your patience. Wayde
Happy Halloween!

Wayde Robson

#10 of 12 OFFLINE   ChrisWiggles

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Posted April 14 2004 - 10:48 AM

Satellite is usually pretty heavily compressed, so you won't be able to make it look much better. As I explained, you can only try to do so much, crappy feed will look relatively crappy no matter what you try to do with it. Good quality, from something like DVD, can be upscaled quite well to good effect, but again, while there may be significant benefits especially for DVD, other poor sources, like VHS and such, still won;t look that hot.

#11 of 12 OFFLINE   Matthew Todd

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Posted April 14 2004 - 11:11 AM

I *think* that the DTV tuner and a scaler are actually separate and different. A DTV tuner will just allow you to "tune" to a digital ATSC signal. These signals may be at various resolutions, depending on the source. For example, I think that Fox's DTV signal is 480p, NBC and CBS use 1080i, while ABC uses 720p. DTV signals that are 720p and 1080i are the best that DTV has to offer, and are known as HDTV. Some TVs that you buy will come with a DTV tuner, although I believe most will not. Most of the new "digital" TVs I think come with a built in scaler, because most TVs are designed to only output at one resolution or a couple related resolutions (for example 480p and 1080i) DTV tuners though do provide some amount of scaling, in that whatever the source coming in (whether it be 480p, 720p, 1080i), you can set the DTV tuner to output at a particular resolution. Mine offers output of 480i, 480p, 720p or 1080i. That is scaling, although it doesn't let you do much like a dedicated scaler or HTPC would. For example, you can't run your DVD player through a DTV tuner to scale it up (as far as I know). The DTV tuner generally just has an RF input, and that's it. If you tried to feed it NTSC stuff, I doubt it would know what to do with it. It is an ATSC DTV tuner.
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#12 of 12 OFFLINE   Wayde_R

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Posted April 14 2004 - 01:32 PM

Thanks Mathew, I think you're right. I learned a bit more and read some other good advice out there. I was totally wrong thinking that a DTV tuner does any sort of scaling or upsampling. It only tunes in broadcasts through the air. A DTV tuner is totally useless in Canada unless you're close to the border of the US. most HDTVs have some sort of built in scaler (as I understand it). But they're not created equal and you have to really take good long looks at picture quality from a variety of sources and decide what looks good to you. It's unfair to judge DVD picture quality against that of a satelite reciever. Different channels/shows introduce their own problems video compression and whatever else. Even some HD broadcasts aren't 100% HD, I saw some menu items pop up, marquees and overlaid video footage on top of an otherwise pure HD broadcast that just looked horrible. So it's pretty inconsistent when watching TV. I think that about does it for my questions. Thanks again. Wayde Robson
Happy Halloween!

Wayde Robson




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