What is the difference between a scaler and a doubler / quadruper?
-
Now Available: Tech Talk Podcast with Scott Wilkinson, Episode 19 Click here for details.
- Status
1 - 9 of 9 Posts
Doubler = double the frame rate of standard NTSC video (480P, or progressive, vs 480i, or interlaced).
Quadrupler = quadrupled frame rate, plus more pixels per line in some cases. 960P vs 480i.
Scaler = flexibility to change resolution and refresh (frame) rate to any of several preset rates or anything you want, depending on model and sophistication (read that, cost). These are more suitable to CRT's because of the anamorphic and HDTV modes needing less resolution due to the fact that the lines are already being squeezed closer. Digital (fixed res) PJ's can also benefit from scalers in their ability to scale to exactly the native rate of the digital PJ's panels or chips. However, a lot of money can be saved by simply going to a good quality doubler due to the fact that you take the PJ out of the equation for the video decoding and the initial doubling duties. Most digital PJ's do a very good job of scaling up from 640 x 480 (480P), while doing a terrible job all the way from NTSC, up.
Quadrupler = quadrupled frame rate, plus more pixels per line in some cases. 960P vs 480i.
Scaler = flexibility to change resolution and refresh (frame) rate to any of several preset rates or anything you want, depending on model and sophistication (read that, cost). These are more suitable to CRT's because of the anamorphic and HDTV modes needing less resolution due to the fact that the lines are already being squeezed closer. Digital (fixed res) PJ's can also benefit from scalers in their ability to scale to exactly the native rate of the digital PJ's panels or chips. However, a lot of money can be saved by simply going to a good quality doubler due to the fact that you take the PJ out of the equation for the video decoding and the initial doubling duties. Most digital PJ's do a very good job of scaling up from 640 x 480 (480P), while doing a terrible job all the way from NTSC, up.
Quote:
I'm getting an NEC XG series PJ.
Do I need to get a scaler or a quadrupler?
I still don't understand the difference.
Is it that a scaler is a flexible doubler / quadrupler?
| Originally posted by M NEWMAN Doubler = double the frame rate of standard NTSC video (480P, or progressive, vs 480i, or interlaced). Quadrupler = quadrupled frame rate, plus more pixels per line in some cases. 960P vs 480i. Scaler = flexibility to change resolution and refresh (frame) rate to any of several preset rates or anything you want, depending on model and sophistication (read that, cost). These are more suitable to CRT's because of the anamorphic and HDTV modes needing less resolution due to the fact that the lines are already being squeezed closer. Digital (fixed res) PJ's can also benefit from scalers in their ability to scale to exactly the native rate of the digital PJ's panels or chips. However, a lot of money can be saved by simply going to a good quality doubler due to the fact that you take the PJ out of the equation for the video decoding and the initial doubling duties. Most digital PJ's do a very good job of scaling up from 640 x 480 (480P), while doing a terrible job all the way from NTSC, up. |
Do I need to get a scaler or a quadrupler?
I still don't understand the difference.
Is it that a scaler is a flexible doubler / quadrupler?
Joined
·
4,801 Posts
Guys
Dull normal TV broadcasts, as seen for many years, must adhere to a transmission standard established by the National Television Standards Committee, hence the use of the acronym "NTSC" to describe the signal which is 480i, or 480 tv lines, interlaced. The signal is sent 60 times a second; on the first pass lines 1,3,5,7 ...... are transmitted, then the scan retraces back to the top of the frame and lines 2, 4, 6, 8 ..... are sent. It takes two vertical sweeps, a pair every 30th of a second, to draw 480 visible lines at 30 frames per second. Due to the limits of human vision, this happens fast enough that it appears mostly as seamless motion. The NTSC system is also referred to as 525 lines, but only 480 lines have visible pixels; the rest are blanked, used for VITS or captioning, or are lost to retrace. 480i looks okay on a 25" tv from ten feet away, but when you magnify it on a quality projector one can clearly see gaps and jitter between the scan lines, the image is not continuous or filmlike. A doubler will sample the 480i signal, digitize it in memory briefly, then draw the image with all 480 lines every 60th of a second. Now we have 480 progressive, and scan lines become less intrusive, at least on a seven inch CRT. However, eight and nine inch CRTs have more potential resolution, and usually feature higher bandwidth and superior lenses. A good eight inch projector is capable enough to resolve gaps between scan lines at 480p; to eliminate these pesky gaps it requires drawing more scan lines per frame; 720p is usually sufficient, this is line-tripling. Triplers are more sophisticated, and good ones are usually $4000 and up. Just drawing more lines isn't enough, the accuracy of colors and fine details must be recreated digitally to avoid distracting artifacts. Some nine inch CRTs will still show gaps at 720p so a line quadrupler is often specified; it samples the same 480i at the input but outputs it in more lines per frame. This is harder to engineer than a tripler so a good quadrupler is usually costly, $5000 and up. The HTPC has generated much excitement by making scaling of DVD playback very affordable and with superb results; as input cards for PCs become improved it may be possible to do quality scaling entirely in the PC. Many of us are very excited about the proliferation of HDTV; High Definition Televsion inherently uses more lines per frame, with shorter raster heights that pack the scan lines close together; this requires the use of more bandwidth to transmit, the image quality is stunning. 1080i and 720p are currently the formats most widely used by HD broadcasters.
Dull normal TV broadcasts, as seen for many years, must adhere to a transmission standard established by the National Television Standards Committee, hence the use of the acronym "NTSC" to describe the signal which is 480i, or 480 tv lines, interlaced. The signal is sent 60 times a second; on the first pass lines 1,3,5,7 ...... are transmitted, then the scan retraces back to the top of the frame and lines 2, 4, 6, 8 ..... are sent. It takes two vertical sweeps, a pair every 30th of a second, to draw 480 visible lines at 30 frames per second. Due to the limits of human vision, this happens fast enough that it appears mostly as seamless motion. The NTSC system is also referred to as 525 lines, but only 480 lines have visible pixels; the rest are blanked, used for VITS or captioning, or are lost to retrace. 480i looks okay on a 25" tv from ten feet away, but when you magnify it on a quality projector one can clearly see gaps and jitter between the scan lines, the image is not continuous or filmlike. A doubler will sample the 480i signal, digitize it in memory briefly, then draw the image with all 480 lines every 60th of a second. Now we have 480 progressive, and scan lines become less intrusive, at least on a seven inch CRT. However, eight and nine inch CRTs have more potential resolution, and usually feature higher bandwidth and superior lenses. A good eight inch projector is capable enough to resolve gaps between scan lines at 480p; to eliminate these pesky gaps it requires drawing more scan lines per frame; 720p is usually sufficient, this is line-tripling. Triplers are more sophisticated, and good ones are usually $4000 and up. Just drawing more lines isn't enough, the accuracy of colors and fine details must be recreated digitally to avoid distracting artifacts. Some nine inch CRTs will still show gaps at 720p so a line quadrupler is often specified; it samples the same 480i at the input but outputs it in more lines per frame. This is harder to engineer than a tripler so a good quadrupler is usually costly, $5000 and up. The HTPC has generated much excitement by making scaling of DVD playback very affordable and with superb results; as input cards for PCs become improved it may be possible to do quality scaling entirely in the PC. Many of us are very excited about the proliferation of HDTV; High Definition Televsion inherently uses more lines per frame, with shorter raster heights that pack the scan lines close together; this requires the use of more bandwidth to transmit, the image quality is stunning. 1080i and 720p are currently the formats most widely used by HD broadcasters.
Joined
·
2,251 Posts
Quote:
I don't know right off hand what kind of bandwidth your XG supports - someone with your projector should chime and let you know - but, put simply - yes, a scaler is a kind of flexible doubler/quadruler. A good scaler will do what a doubler or quadrupler will do and more.
Here's a simple way to think of it - don't correct me on the details, guys - I'm trying to simplify this:
Plain old NTSC video is 640x480, 30 frames per second - put simply. But each frame is made up of two fields - it's interlaced. The fields are displayed on all the odd lines in the frame, then all the even fields in the frame (or vice-versa). So, really, every 60th of a second, you're getting an image that is something like 640x240, but with black spaces where the next set of fields will be. Sometimes - especially on a large screen front-projector - you'll see the big, fat hairy horizontal lines that make up interlaced video.
* A doubler will "double" the number of scan lines, so that instead of 60 interlaced fields per second, you'll get 60 full frames per second (with double the resolution).
* A quadrupler doubles, then doubles again, so you end up with say 60 frames per second, but 1280x960 instead of 640x480 - thereby hiding the scan lines that your projector uses to "draw" the image on the CRT's.
* A scaler will take a normal video input, and "scale" the video to some preset resolution and timing - usually to match a display's - or projector's - optimum output.
So, for instance, if you had a projector that was capable of running at only 1024x768, you could use a scaler to scale the video input to 1024x768.
Hope that helps. Do a google search for line doubler or line quadrupler - there's lots of information on the web on the topic - even some tutorials. Probably even some discussion threads on the forum.
SC
| Originally posted by Rohan I'm getting an NEC XG series PJ. Do I need to get a scaler or a quadrupler? I still don't understand the difference. Is it that a scaler is a flexible doubler / quadrupler? |
Here's a simple way to think of it - don't correct me on the details, guys - I'm trying to simplify this:
Plain old NTSC video is 640x480, 30 frames per second - put simply. But each frame is made up of two fields - it's interlaced. The fields are displayed on all the odd lines in the frame, then all the even fields in the frame (or vice-versa). So, really, every 60th of a second, you're getting an image that is something like 640x240, but with black spaces where the next set of fields will be. Sometimes - especially on a large screen front-projector - you'll see the big, fat hairy horizontal lines that make up interlaced video.
* A doubler will "double" the number of scan lines, so that instead of 60 interlaced fields per second, you'll get 60 full frames per second (with double the resolution).
* A quadrupler doubles, then doubles again, so you end up with say 60 frames per second, but 1280x960 instead of 640x480 - thereby hiding the scan lines that your projector uses to "draw" the image on the CRT's.
* A scaler will take a normal video input, and "scale" the video to some preset resolution and timing - usually to match a display's - or projector's - optimum output.
So, for instance, if you had a projector that was capable of running at only 1024x768, you could use a scaler to scale the video input to 1024x768.
Hope that helps. Do a google search for line doubler or line quadrupler - there's lots of information on the web on the topic - even some tutorials. Probably even some discussion threads on the forum.
SC
Joined
·
4,583 Posts
i have a NEC XG852 which Doug Baisey set up. I have it configured for 1280x720 and 1440x960. To me, 1280x720 looks better than 1440x960 since the higher res seems a bit soft. Doug also said it was more difficult to set it up for 1440x960. If you are getting a liquid coupled unit (110LC or 135LC) the higher resolution makes 1440x960 the better choice.
I'm new to CRTs and home theater myself and have a related question. I understand that a "line doubler" is actually de-interlacing and presenting all the original video information in a progressive rather than interlaced format. Or at least that is what I think is going on. But when you are using a line tripler or quadrupler what information is making up the additional 1 or 2 scan lines? I thought most source material is pretty much only available in 480p(excluding high def broadcasts of which there arent that many right now). So with 480 lines in your source where do you get the additional lines/data for 720 or 1080? Maybe I'm still a lot more clueless than I thought I was. Please help!
Joined
·
2,251 Posts
It's lots and lots of math, boys. You're right, high-end doublers, triplers, and scalers do dissect the image. They do motion analysis (look for things that are moving vs. things that are not), and interpolate or do not interpolate based on what they find in the image. The try to detect in the source material whether it was shot on film or video and reassemble the progressive scan image appropriately. It's a very complex process, which is why they aren't cheap boxes.
SC
SC
1 - 9 of 9 Posts
- Status
Join the discussion
