Saturday, January 1, 2011

【 Weak current College 】 resolution and clarity of the distinction, between 】



Although in many magazines and articles, see the "resolution", but not a different person always has a different view, see viewing more confused than not. Home appliance salesman who often put a lot of data to meet "before us: 600-800" line of televisions, 480P, 720P, 1080I, VGA, SVGA, XGA, and so on, not to mention is the ordinary consumers, I see even the "experts" are also covered. So I hope the following explanation lets readers know these data, even if you remember the moment, you can know the basic concepts, the next time you have to learn not for salesman with your random about it by this article may be brought to him in class.

1, pixel composition image

Image by continuous rapid emergence of still images, when we speak image resolution time refers to the composition of the image pixels. Think about drawing the text of the paper used, when you fill the appropriate color, you'll get an image. When we zoom in this section, we saw the composition of the picture in pixels. Pixel dots line, the line is composed of an image, a lot of images continuously up image composition activities.

2, vertical sharpness

Because of the clarity of the "vertical" the easier to understand, we'll start from simple. "Vertical sharpness" is an image from top to bottom, composed by the number of pixels. Since each one horizontal scan lines form a vertical pixels, so we can say, "vertical sharpness" is an image by the number of "horizontal scan line". An image how many horizontal scan line is determined by the signal format, so long as the signal format determines the vertical definition is defined. For PAL system, no matter how you look at the TV, VCR, VCD, LD, or DVD, you finally see the vertical resolution is 625. Further, we see a picture and not by all 625 lines. In fact, the present period, there are no hidden 49 lines for the transmission of other information, such as closed caption, teletext, test signal, etc., at the same time when the electron beam from the bottom to the top to start scanning the next images also take some time. Get rid of these we "see" number of rows, we see a picture in fact up to 576 lines. This is also the highest pal's vertical resolution. Further, because the imaging and human visual characteristics, the 576 lines just theoretical resolution. Actually you "see" the vertical resolution of the image must be multiplied by a correction factor of less than 1, this coefficient is called Kell factor. For interlaced, Kell factor 0.7, PAL, the last displayed vertical sharpness of the image is about 400 lines. Actually watch the test pattern, because it does not consider Kell factor, the observation of the vertical definition usually can reach 450 lines or so. You can test the vertical definition can also test the level of sharpness.

3. horizontal resolution

As we mentioned above, the vertical definition decided solely by the signal format, this is very easy to understand. The horizontal resolution is most easily confusing concept, one of the biggest problems is that there are several levels of clarity. I know some of the IT industry, their computer resolution, but do not know in home theater should be how to use the term "resolution". This is due to a variety of expressions can consist of many kinds of data to express, on various occasions, the same data may be completely different performance.

Computer areas in computer industry often use composition image number of pixels to represent the resolution, that is, the number of horizontal pixels x vertical pixels. Such as: VGA: 640 × 480; 800 x 600 SVGA:; XGA: 1024 × 768.

The field of video in the video realm, we are more accustomed to using "every image height" number of pixels representing the horizontal resolution, and call it "television". The origin of this custom dates back to the TV set was born in 60 years ago. At that time, because the signal format have decided on the vertical resolution of the image, so the experts think is used and how the vertical definition related to represent the level of sharpness. In other words, the end is the horizontal direction more clarity. In other words, the end is horizontal or vertical direction more clearly, the relative clarity means that you can see at a glance. Figure 4-horizontal resolution and vertical articulation of the relationship. For this reason, the level of sharpness (TV lines) is defined as: and screen height equal horizontally to display the number of pixels. In this definition the sharpness is called the "TV". Therefore, when you still hear about video signal number definition, it does not mean the most to the left from the image to the right of the number of pixels, but rather in and image height the same horizontal width on the number of pixels.
Please look at your TV or computer monitor, you will find they are not a square, its display ratio is 4: 3. In other words, to get the vertical definition is the same as the horizontal resolution, horizontal pixels to achieve vertical articulation of 4/3 times. For DVD, NTSC system is 720 × 480 pixels, and PAL is 720 × 576 pixels. NTSC and PAL of horizontal resolution is 720 × 3/4 = 540 line. DVD in NTSC system, the horizontal resolution is higher than the vertical definition (540 lines > 480 lines); PAL DVDs, horizontal resolution is slightly lower than the vertical definition (540 lines > 576 lines).

4. definition of determinants

Image sharpness = source image quality by processing circuit processing level × display imaging quality. These three factors are equally important to determine the final quality of the image, one can rarely (as in Figure 6). Any link errors will cause the final image of horizontal resolution (Figure 7). Even if the product improves processing circuit performance or imaging performance, but if you do not have the appropriateSignal source, nor can significantly improve the image quality (shown in Figure 8, 9).

5, bandwidth, and the relationship of pixels

If this is the analog signal to digital display equipment on display, we first need to be emulated → digital conversion; whereas if it is a digital signal to analog display device displayed, we first need to be digitally → simulation of conversion.

In the analog signal, we use the bandwidth to represent the signal quality. In the area of digital signal, we use the number of pixels that make up the image to represent the image quality. PAL video signal bandwidth is 6MHz. Through standard digital sampling, is 720 × 576 image, the two statements had expressed the same quality of the image. As we describe a plate of food, the Chinese talk about "good" and "delicious" speak English, the meaning is the same.

6. calculation from pixel level definition
VGA (640 × 480, 4: 3 screen): 480 TV lines; SVGA (800 x 600, 4: 3 screen): 600 TV lines; XGA (1024 × 768, 4: 3 screen): 768 TV line; 720P (1280 × 720, 16: 9 screen): 720 TV line; 1080I (1920 x 1080, 16: 9 screen): 1080 TV cable.

7, from bandwidth calculation of horizontal resolution
Clarity of H = 2 × T÷A×F. Where t is the horizontal scan range time, on a television image format, it is fixed; the aspect ratio of the picture tube A (4: 3 or 16: 9), letter F to television, extended bandwidth and A constant T.
To PAL, the degree of signal maximum bandwidth for 6MHz, row frequency for 15625Hz/s. If the image signal is the highest frequency 6MHz single frequency, then each row shows 6000000/15625 = 384 week. If you are a half week to white, negative half week to black, each row will show the section 768 cycle of black and white lines. Each line cycle is divided into positive Cheng and backward, only being there on the decomposition of labor. PAL standard 18% backward, so each row displays a maximum of Betty's black and white line will not exceed the total number of 768 × 0.82 = 629.76. In other words, the PAL standard decomposition of limit is 630 black and white line, converted into TV line of argument is 470 TV lines or so. Of course you do not have such a complex calculation, you can use an algorithm to calculate the experience: 1MHz bandwidth = 81 TV cable. This is not difficult to find the VHS video recorder-: 3MHz bandwidth, about 240 lines; NTSC system TV: 4MHz bandwidth, about 320 lines; PAL TV: 6MHz bandwidth, about 480 lines; DVD: 6.75MHz, 540 lines or so.
8, popular data and terminology explained
1250 lines, 31250 line, 30MHz bandwidth, Megapixel, Super fine picture tube, these are salesman "selling" to your pop data and, if you have not read this article before, you might be confused. Now that you have a previous knowledge to do – and we can to uncover these data terminology and veil. The same is the word "line", probably talk about "horizontal scan line" (vertical resolution), or it may be said on the screen horizontally across a number of lines that can also be a talk at the height of the horizontal width of the screen on the wire (TV lines).
1250 line this is the double frequency scanning television terminology. Due to the doubling of scanning stresses field scan frequency up to twice the original 625 per frame scan, now became the 1250 lines, known as 1250 lines, here's the "bars" refers to the horizontal scan line.
31250 line this is a bluffing data refers to within a second, doubling the TV total scan lines, it was 31250 and every frame scan 1250 lines are the same meaning (31250/seconds = 1250 line/frame x 25 frames/sec). This is one step further, it is 2 million lines, of course, there's 2 million line refers to the lines per minute (31250 lines/sec × 60 seconds/minutes). Here's the "bars" also refers to the horizontal scan line.
30MHz bandwidth as previously we introduced to the calculated 30MHz bandwidth is 1920 × 1080. Note that for PAL signal source, bandwidth only when using 6MHz 30MHz processing bandwidth Imaging is a waste, and workers can improve image quality. Because even with30MHz bandwidth, also must have the signal source 30MHz (HDTV), and can display 1920 × 1080 of picture tubes, without the support of both 30MHz just a bluffing data only.

MEGA Brands of televisions is some 200 m pixel processing, claims that you can do to improve image clarity. The "mega" come from? the TV's digital processing circuitry incorporates a 1920 × 1080 HDTV, so each picture has the "mega".

However, if your TV signal source is 720 × 576 (41.5 megapixels), even if the processing performance and good to the last image is still a 720 × 576 (41.5 megapixels). In the "mega" processing, each 5 pixels is actually identical to one pixel. And don't forget, we've taken the image clarity of the three elements appear in this article, although a mega-deal, but the final picture tube or ordinary CRT, or only display 720 × 576 (41.5 megapixels), so even the 2 million pixel processing, also did not improve image quality. Figure 10-megapixel treatment: in the left figure, each black points from four small black dots, gray dots also consists of four small gray dots, this image of the actual viewing and right of exactly the same. In fact, the tube each point by the red, green, Blue three small dots and each small point consists of innumerable phosphor composition, these innumerable phosphor dots displayed is "the same pixels", but obviously we cannot call resolution is from "these innumerable phosphor dots".

Therefore, 30MHz bandwidth and mega process is the same meaning. Only 30MHz follows the traditional analog signal processing of the call, and mega is the new "digital" popular language. These two terms in fact expression is the same one performance indicators.

Super fine picture tube "mega" cause injury in the CRT is not a "mega", so the final image sharpness due to the CRT and greatly reduced, and the general approach. That if the "200 million-pixel" processing + "Super fine picture tube"? this distance a better image and near a step, but have not yet achieved. Because only the last three elements of the two elements. You must be the first element--signal source of support. In the absence of high-definition signal source and supported by a "mega" + Super fine picture tube and the most common TV and there is no essential difference. So, when there is a high-definition and high-definition picture tube processing circuits and matching high-definition television before you buy "HDTV". Otherwise, the high price of "Advanced" TV is really just the display only, as you see in the high-definition television programme, see VCD image quality or VCD level is not high-definition of




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