Digital brake and glitches in the image

here is the second part of the most terrible articles about the figure and its glitches, so if you have not read for moral training begin from the first part: 50 or 100 Hz bf

Dear friends, we are guilty that the world around us - not digital and simple analog? bn our eyes?, anyone has digital vision? What is there to be surprised that the first attempt to digitize the signal, and then convert it back to analog, do not always lead to a good result. Let's define some terms:

  • Analog signal (analog) signal, continuously varying in time, in our case this is all that we see with our eyes and hear with our ears
  • Digital signal (number) - a set of codes consisting of "0" and "1" which is encoded in the conventional analog signal
  • Digitization is the process of converting each analog signal into a digital code, the device that allows it to do are called ADC (Andtax Cdigital Wreobrazovateli), it is logical that the reverse process - the translation of digital code to an analog signal, perform a DAC (CIFRO AndWreobrazovateli)
  • Digitization of the analog signal
  • Let's skip the complicated definitions, physico-technical details and focus on the process digitizing. Before You graph (sine wave), let's pretend this is a normal sound (like PI-and-and-and...)

    digitizing the analog signal

    As you can see, the line on the chart (amplitude) is changed continuously in every moment of time. Converter (ADC) scans the signal in certain time intervals (sampling rate) and writes its value (the number of which, incidentally, is also limited by the ADC). This value will hold until then, until a next scanning and the value will not change. What happens to the line amplitude between periods of scan - Converter knows. As you can see, at the entrance we had a smooth line, and the output - stage (this is called discretized signal)

    the Discretized signal

    As our heads (eyes and ears) are not yet equipped with built-in USB connector, we have a digital signal to decode it (translate it back to analog). At this stage, the same errors occur because we need to restore the smoothness and continuity of the "patch-cut" signal. The result is a dual conversion (analog - digital and digit - analog) accumulated errors are not weak to distort the original audio or image

    Recovered signal

    Of course, the scanning frequency in modern converters is very large, and the step is very small, so they are able to see and identify the slightest changes in the signal, hence the quality of digital records (photos, audio, movies), but back to "our sheep," televisions and the familiar simple color pictures ab

  • Color patches - error indexing
  • Don't know about You, but I don't like movies, fully digitized (like Beowulf), if it was a cartoon - everything is clear and no issues, but when trying to present a "decoy" for the real world... it is Impossible to fully digitize a torrent of water, burning fire, rustling leaves on trees... they don't fit in any one equation (known as equations of motion), the computer can't keep up bl

    Cartoons and movies with a huge amount of computer special effects are always clear and beautiful as all the colors in them are indexed. However, no matter how tried computer graphics specialists, our eye is difficult to cheat, he will still see and distinguish the live image from artificially created. See how clearly the difference between live photography and computer clone:

    Analog and digitized image of man

    Despite the fact that the actors were plastered with huge number of sensors, eyes stubbornly sees only the schedule and refuses to believe that image - really

    Computer animation of human

    Real signal has too many shades, the technique does not manage to catch them all and handle it, therefore when viewing the analog signal on 100Hz TVs, it was possible to see something like this:

    Analogowy signal at 100 Hz TVs

    TV indexed colors as I could, but to catch all the shades, especially in motion - it was not under force because of the weakness of the processor and complexity of the treatment process

  • Pixel errors of addition
  • You have not forgotten what the progressive scan? Under normal signal (interlaced) television (digital signal processing) have two fields form four full frame (for 100Hz), where did I get them? In order for additional frames appeared, the TV was a pattern of "remembering". She remembered the first half frame and detained him until the signal of the second half. The scheme of the "folded" them and get a whole frame (all the lines: even and odd). It the rays of a CRT or digital matrix needs to prescribe. Prescribed, now you can go for a smoke break, as, until the next half of the signal, there was really nothing, and that something must be done bn

    That was the main "curse" 100Hz TV running on a normal signal. Shaping shots was nothing, had something "wise": to prescribe the same frame several times, folding half frame from the past frame with polyedrum from the new or just "pretend" that spells out the real Palestrina cadres, prescribing the "support personnel" among the main. As a result of all the "additions" on moving objects often had the pixel error, which was clearly visible in close-UPS or when watching TV from a close distance. If simple TV has ordered all smoothly and consistently, according to the input signal (original with increase):

    Analog zoom

    that digital could produce the "addition processing" like this:

    Pixel errors of addition

    The advent of the camera progressive scan significantly and greatly reduced the number of errors they gave 25 full (rather than 50 interlaced) frames, and professional - to 200 ay Now there are plenty to form a real footage on a TV when shooting new films and programs, and from the "old Keane" - You will forgive me, no 100 or 200Hz is not done ( and 25 full - also where to get more three frame to 100 Hz? ah )

  • Extra shots
  • As You know, in order to watch the movie on a TV with interlaced 100Hz, you need (ideally, and it will be right) to have four full frames per second. on the input (the received signal). As it is, at the moment, almost impossible, appears in the image "brake", well visible to the eye. Due to the artificial creation scheme for additional frames, the image remains on the screen for a little longer than expected, but change is happening very quickly

    Powerful filters and expansion joints movement trying to smooth out this process, however, manage is not always. In the end, our eyes "see" one frame twice longer than necessary. What comes out of it but tired eyes, read on bs

    in Front of You a small fragment of the famous film (a few seconds)

    If you watch it on your TV (or monitor) with the desired frequency sweep - all smooth and beautiful, no "smazannost" we wouldn't notice (eye sequentially scanned frame by frame and do not strain). Now lay it on the staff, "time of cutting" one frame corresponds to a real frequency sweep:

    Storyboard sweep

    As you can see, the first frame - clear, 2, and 3 - oiled (matter movement), and the last (he's eighth) is again clear. Now the question is: how is the filter with the "compensator" should be folded first and the second frame to get the extra frames? He has the choice of either "spread" or add a non-existent sharpness. And then, and another is "extra" to our eyes, because in real life they would "see" this piece exactly (blurry frames), our eyes do not work at a frequency of 100 Hz, they have more inertia bk

    Who does not believe, try it when you go fast in the car, watch the edges of the fence or the road markings from the side window. It turns out to snatch a rib or a dashed line clearly and sharply? No, the eyes go into the mode of "seamless browsing" and able to "grab" only one "detail" and then, if for her to start a "watch" eye, and even with a turn of the head be

  • Unnecessary sharpness
  • If the format recording and playback are identical - no problems, imagine a situation in which the recording frame rate is higher than the frequency of the TV or TV - just the "brake" and does not have time to work out changes in the signal on your screen (and slow down it will be because the process of digitizing and several subsequent transformations with the results of the analog signal at the end - takes a lot of time and forces). Watch fragment (small):

    It is known to all "frame animation, the effect of sharp movements of the skeletons and the lack of smoothness was due to the fact that in every frame "skeleton" is drawn clearly, in contrast to the movements of real actors. Please note swords, we are absolutely not annoying "razmeshannoy" the sword of the main character, but the sharp jump of the skeleton:

    Living Iphigenie and animationSharp transitions in the animation

    This could happen when the "time of exposure" (photography) too little and pause between shots. Achieve high definition recording of the signal, this effect must be considered, especially when very rapid movements or high speeds of the subject:

    the Motion of high speed

    In order to remove the machine in the desired field and show its movements without slow-motion effect - you need at least 500Hz instrument, and: the camera and the TV. Who are little, for the sake of experiment, to move quickly, "mouse", and follow its pointer on the screen with your eyes. Well? dq

  • goodbye noise, Hello, Hello, squares
  • Digital processing and signal transmission completely removes the noise ("ripple" on the image), however, with poor signal or processing errors, particularly in dynamic or complex (sky, water) stories, "ripple" was replaced by the squares (the ones with zeros messed up and the digital code is partially damaged)

    Squares on the image

    A "square picture" is often seen in poor satellite signal or viewing a poor quality recording with a DVD. Too complicated portions of an image if handled incorrectly or a weak CPU, can be replaced by "squares" with the "middle value" of colors in it

    What can we expect next, wait and see, but for now... the struggle of the figures and the analog continues ab

    Link to this story: http://en.rem-tv.net/publ/3-1-0-52

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