AV1 - Television - the art of image transmission and...

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Unformatted text preview: Television - the art of image transmission and reception CAMERA TELEVISION 1 st question: How to capture an image and convert it into an electrical signal? Early days, camera adopted line scanning 1 No scanning required now, standard remains the same CCD - solid state image recording TELEVISION Electronic signals in PAL, NTSC standards To understand scanning, we need to look at early video camera design 2 Figure 1 J.S. Zarach and Noel M. Morris, Television principles & practice Click Me!! 3 What you have seen only converted the brightness of a single spot to a voltage or current flow. What about converting the entire image plane? A scanning mechanism is required to convert every point on the image to its corresponding voltage or current value. Click Me again !! What does the scanned waveform looks like? 4 Line 1 Line 1 Line 2 Line 3 Line 2 Line 3 Suppose the image looks like the following 5 Line 1 Line 2 Line 3 Frame rate: Number of pictures scanned per second A single picture One second Pic 1 Pic 2 Pic 3 Pic M M Frames/Pictures per second 6 Color images are made up of three primary colors = + + In early days, few people had color TV. Transmitting three images takes up 3 times the bandwidth. Solution: Split image into Luminance and Chrominance. Luminance contains B/W information, very sensitive to our eyes Chrominance supplements color information, less sensitive to us. 7 = + U + V Y B/W TELEVISION Color TELEVISION Wide bandwidth Narrow bandwidth 8 Luminance (Black and White) signal Color (Chrominance) signal + = Sound = TELEVISION How to combine them together? 9 f VSB Chroma at 4.43 MHz Sound at 6 MHz The components are modulated and grouped into different parts of the frequency spectrum.-1.75 MHz 10 10 Figure 2 Amplitude Modulator Frequency Modulator Syn. Pulses Generator RF Modulator Audio Signal Video Signal M Y Y (I.F.) 11 11 How are video signals generated and recovered on the Television in practice? The basic concept has been covered. A major consideration: bandwidth Bandwidth determined by: Resolution and Pictures/second. Objective: To send as much information as possible with less amount of bandwidth 12 12 Video camera in the early days Synchronization Interlaced scanning Existing TV standards are consequences of early development. Image Acquisition Scanning Image reconstruction Synchroniza-tion Bandwidth restriction Interlaced Scanning Color information Frequency Interleaving Future Bread and Butter More pictures/sec....
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AV1 - Television - the art of image transmission and...

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