Computer Science 1033 Topic 8 Notes

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Western University
Computer Science
Computer Science 1033A/B
Vivi Tryphonopolous

Video (part 1) Video: Sequence of still images or frames that create the illusion of movement when played in succession Video Editing  Download video from camcorder to computer  Analog camcorder: o Electronic impulses are recorded o Must be converted using a video capture card to digital before it can be used  Digital video camcorder: o Information is sent as 0s and 1s, and therefore there is no need to convert o Little bit of compression is done within the camera (DV 25 Format)  Pixel dimension : 720 x 480 (3:2 ratio)  Frame aspect ratio: 4:3 or 16:9  Data rate: 25 Megabits per second  Frame rate: 29.97 fps  Color sampling: YUV 4:1:1 (compression)  Color compression in the camera o For still images, RGB color model is commonly used o For video, YUV (YIQ) or YCbCr model is used  Y = Luminance / Brightness (used by black and white TV)  UV or CbCr = Chrominance / Color / Hue o Human eye detects change in brightness because we have more rods (which detect brightness) compared to cones (which detect color). Therefore, video compression reduces color information and keeps brightness info. o Color sampling (compression technique for video):  X:Y:Z, where X = brightness and Y, Z = max compression  4 = no compression and 0 = max compression  Downloading video to computer: o Firewire (i.Link, IEEE1394)  Means by which information can be sent from the camcorder directly to the computer  High speed serial data connection that allows the output of the camera to be fed directly into a computer in digitized format  Major manufactures have agreed to use common digital tape format and firewall method o History: Firewire is initiated by Apple and IEEE in 1980s, with original transmission at 400 Mbps  Used to have patent of $0.25 charged to any computers that used it, and other hardware cost more  Firewire 400 with ability to connect camcorders and move videos from each other  Firewire 200 does video technology that allows videos to be copied onto a camcorder  In 2011, Thunderbolt technology was released, with 10 Gbps. o USB: PC’s decision against firewire  USB 1.1: Transmit at 12 Mbps and was too slow for mice, keyboards, and printers  USB 2.0: 480 Mbps and backward compatible  Edit digital video  Output video Televisions  Frame aspect ratio: Ratio of width to height of the image frame  NTSC standard: o Regular analog TV broadcasting using NTSC standard began in the US since 1939 to present day. o Frame rate was 30 fps, but reduced to 29.97 fps to accommodate color information when it was introduced o Standard DV frame size:  3:2 ratio (1.5)  Pixels are not squares and distorted o High definition DV frame size:  1440 x 1080: 4:3 ratio and non-square pixels  1280 x 720: 16:9 ratio and square pixels  PAL standard: o Standard used by Britain, Europe, and other countries o Frame rate set at 25 fps o Pal Standard DV frame size:  720 x 576 pixels  4:3 ratio (1.3) and square pixels  Interlacing: An electron beam / gun activate the dots, and the gun scans through the dots horizontally. o Field: Each horizontal pass o Dot: Phosphor dots that our eyes see on the screen o A complete scan is when the gun starts at the top left, and scans until it gets to the bottom right. o Before 1996, all televisions were broadcasted using interlaced display and fields  Original TV: o Electron gun beam gun activate the dots o Interlacing is done in interlacing effect (line odd numbers, then line even numbers) o Lower resolution (480i: 640 x 480 pixels)  Flat screen TV: o Flat grid of screens o Interlacing is done in progressive effect (line 1, 2, 3, 4, 5…) o Higher resolution(720p: 1280 x 720 pixels) (1080p: 1920 x 1080 pixels) o Experiments began in 1950s and 60s, but only adopted by a single station in 1996. Displaying Video Format Lines of resolution (image quality) VHS, VHS-C 240 lines 8mm 240 lines Hi 8mm 400 lines Most older TVs 480 lines DV 8mm, Mini DV 480 lines HD TV 720 or 1080 lines Review Questions 1. Which is the fastest? Firewire 400, USB 2.0, or Thunderbolt? 2. Does every apple have a firewire port? 3. What is the frame rate for NTSC TVs in the 1980s 4. What is the frame ratio for HD TVs 5. What does 1080p mean? 6. What is the color sampling method that offers 0% compression? 7. Name two types of data transfer methods you can use to move your video from the camcorder to computer 8. How many scan liens are there on an analog TV from the
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