- Do I need a video processor?
The short answer is this: if you see video artifacts, then you may benefit from a video processor. Video artifacts usually become bothersome as the viewed image becomes larger, as video was never designed to be blown up to large sizes.
As you may find many projectors, RPTVs and plasmas have some sort of scaler and/or deinterlacer built in, and they produce excellent quality. However in most cases, the integrated video processing is rather lackluster. Therefore, many large venue setups will benefit from some sort of video processing. What you need depends on what type of display you have, and whether you are bothered by any artifacts you see.
If you see combing, jaggies, pixilation, or other artifacts, chances are a good quality video processor will help resolve them to some degree.
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- Do I need a scaler or deinterlacer?
While a scaler and deinterlacer are video processors, they fall into different categories and are used for slightly different applications.
Scalers are typically used with fixed pixel devices, such as LCD TVs, plasma displays, and fixed pixel projectors. As all of these devices have a fixed grid of pixels which the video image must be mapped to, a scaler is the perfect fit for these types of displays. Line triplers and quadruplers usually do not match the frequencies of fixed pixel devices, so they are generally poor choices for fixed pixel devices.
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- What's the difference between a line doubler and a scaler?
We can say that a line doubler is a kind of scaler. More specifically a line doubler is intended to create output video frames with exactly twice the number of scan lines while a scaler usually has several ratios of output scan lines to input scan lines per frame.
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- What are motion artifacts?
For all subject motion in interlaced video, one field, say the even scan lines, will show the movement first, then the next field of odd scan lines shows more movement leapfrogging over the previous field, and so on. A mediocre de-interlacer may construct video frames by blindly weaving together adjacent fields, with the subject motion differences contained within showing up a ghosted double exposure effect. This is also called combing because the feathered side edges suggest the teeth of a comb. A good de-interlacer delivers video with more solid side edges, without this combing.
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- What are jaggies?
Jaggies (jaggedness; stair stepping) are always present on diagonal lines or edges when a picture is represented as scan lines or pixels. For mediocre de-interlacing, plain line doubling or outputting each scan line twice being a reasonable worst case, jaggedness is coarser than the scan line spacing.
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- What kinds of connections should a scaler have?
A scaler should have input connections for all your devices. Usually, a scaler will provide a composite, an s-video, and a component input.
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- Can my TV/Projector use a scaler?
Most newer digital TVs have some sort of deinterlacer and/or scaler built into them. Older TVs do not have a deinterlacer or scaler built in.
The first thing to find out is if your TV accepts a deinterlaced input. To accept this, the TV must either accept some form of an RGBHV signal (i.e. 640x480, 1024x768, 848x600 all of which are progressively scanned) or a progressive component signal (i.e. 480p, 540p, 720p). If your TV only has composite, s-video or RF inputs, it will not support a deinterlaced input.
For most projectors, you will have to determine if your projector can support the frequency needed. To display 480p, your projector must be outfitted with RGBHV or component connections, and able to accept a signal with a 31.5 KHz bandwidth. Similar requirements exist for 720p, 1080i, etc... If your projector only has an s-video or composite input, you can't use a deinterlacer or scaler.
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- What makes DCDi so popular?
DCDi garnered its popularity by being the first "commonly available" algorithm to help deinterlace video. Due to the nature of video sources, it is impossible to deinterlace perfectly. DCDi helps to interpolate the differences between different video frames, which help to reduce jaggies and other artifacts. It is quite noticeable on video based sources, such as news broadcasts and sports.
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- What benefits does SDI add to a scaler?
SDI is a digital connection from a video source to a video receiver/processor. One major source of noise and loss of resolution is the analog to digital conversion of a component or s-video signal.
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- What benefits does DVI add to a scaler?
DVI eliminates a possible digital to analog and analog to digital conversion, resulting in a clearer picture with less noise and more detail. In addition, having a DVI input to the scaler may allow greater flexibility in the future, as DVD players and receivers
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- Do we need scaling for HDTV?
Ideally no. Ideally the display should be able to show all 1080 scan lines (or rows of pixels) of 1080i HDTV, all 720 scan lines of 720p HDTV as-is, and either 960 scan lines (with an additional doubling) or 480 scan lines for 480p. Unfortunately digital fixed pixel displays such as DLP and LCD, and some CRT displays do not have all three of these display modes. They therefore employ scaling.
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- What does "Interlaced" mean? What does "progressive" mean?
Interlaced: The odd scans lines are drawn, then the even scan lines, then the odd scan lines, etc. Progressive scan: All scan lines are drawn in order. Due to limited information transmission capability back in the early days of television, and also for 1080i HDTV today, only enough picture material for a frame every 1/30'th a second was transmitted, and using progressive scan at the same frame rate would have resulted in the top of the picture fading while the bottom was still being drawn. Interlaced scanning was the best compromise.
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- Why does "Progressive" video look better than "Interlaced" video?
With interlaced scan the fading of the odd scan lines as the even lines are being drawn, and vice versa can still be seen. Also the leapfrog effect as motion appears, say first on the odd scan lines, then on the even scan lines, etc. can be seen by some viewers. Progressive scan is intended to give a smoother picture by eliminating these effects.
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- What is/are 480i, 480p, 1080i? What do these numbers mean?
These numbers represent different types (resolutions and rates) of video signals. In general a higher the number indicates a higher resolution. Note that a higher resolution does not necessarily mean a better picture, however, as the capabilities of a signal are only one part in the chain of a good video display system.
The first part of the term represents the number of vertical scan lines per frame: 480i has 480 scan lines in each frame, 540p has 540 scan lines per frame, and 1080i has 1080 scan lines in each frame. Implicit in the number of vertical scan lines is the number of horizontal pixels: 480 imply a resolution of 720x480, 720 imply a resolution of 1280x720 and 1080 implies a resolution of 1920x1080.
The second part indicates if the signal is interlaced (indicated by an "i") or progressive (indicated by a "p"). Thus, 480p is a signal which carries 480 vertical scan lines in a progressive format. 1080i is a signal which carries 1080 vertical lines in an interlaced format.
Note that many higher rate signals (all progressive formats, and 720 and higher rates) cannot be carried by s-video or composite signals, but only by higher bandwidth methods such as RGBHV, DVI or component.
