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Multimedia System

Multimedia System. Faculty of Science Information Technology Safeen Hasan Assist Lecturer. VIDEO PROCESSING. DEFINITION OF VIDEO SIGNAL

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Multimedia System

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  1. Multimedia System Faculty of Science Information Technology SafeenHasan Assist Lecturer

  2. VIDEO PROCESSING • DEFINITION OF VIDEO SIGNAL • Video signal is basically any sequence of time varying images. A still image is a spatial distribution of intensities that remain constant with time. Video signal is treated as a series of images called frames. • An illusion of continuous video is obtained by changing the frames in a faster manner which is generally termed as frame rate.

  3. Analogue Video Signals • The three principal Analogue Video Signal formats are: • NTSC (National Television Systems Committee), • PAL (Phase Alternate Line) and • SECAM (Sequential Color with Memory).

  4. NTSC: • The United States, Japan, and many other countries use a system for broadcasting and displaying video set in 1952 bu National Television Standards Committee. • A single frame of video is made up of 525 horizontal scan lines drawn onto the inside face of a phosphor-coated picture tube every 1/30th of a second.

  5. PAL • The Phase Alternate Line (PAL) system is used in the United Kingdom, Europe, Australia, and South Africa. PAL is an integrated method of adding color to a black-and-white television signal that paints 625 lines at a frame rate 25 frames per second.

  6. SECAM • The Sequential Color and Memory (SECAM) system is used in France, Russia, and few other countries. Although SECAM is a 625-line, 50 Hz system.

  7. High Definition Television (HDTV) • HDTV • High Definition Television (HDTV) provides high resolution in a 16:9 aspect ratio. This aspect ratio allows the viewing of Cinemascope and Panavision movies.

  8. Progressive and Interlaced Scan Pattern • Progressive scan patterns are used for high resolution displays monitors Digital cinema projections. In progressive scan, each frame of picture information is scanned completely to create the video signal. • In interlaced scan pattern, the odd and even lines of each picture are read out in two separate scans of the odd and even fields respectively. This allows good reproduction of movement in the scene at relatively low field rate.

  9. RGB and CMYK Color Spaces • The RGB model, inspired by human vision, is an additive color model in which red, green, and blue light are added together to reproduce a variety of colors. • The RGB model applies to devices that capture and emit color light such as digital cameras, video projectors, LCD/LED TV and computer monitors, and mobile phone displays. • Alternatively, devices that produce materials that reflect light, such as color printers, are governed by the subtractive CMYK (Cyan, Magenta, Yellow, Black) color model.

  10. Spatial Resolution and Frame Rate • The horizontal and vertical resolution of digital video is related to the pixel sampling density, i.e., the number of pixels per unit distance. The number of pixels per line and the number of lines per frame is used to classify video as standard, high, or ultra-high definition. • The visibility of pixellation artifacts varies with the size of the display and the viewing distance.

  11. Spatial Resolution and Frame Rate • The frame/field rate is typically 50/60 Hz, The notation 50i (or 60i) indicates interlaced video with 50 (60) fields/sec, which corresponds to 25 (30) pictures/sec obtained by weaving the two fields together

  12. HDR Image Capture • HDR image capture with a standard dynamic range camera requires taking a sequence of pictures at different exposure levels, where raw pixel exposure data are combined by weighted averaging to obtain a single HDR image

  13. What Frames Are • In video (both analog and high definition), just as in film, images are displayed as Frames.  • There are differences in the way the frames are displayed on a television screen. In terms of traditional video content, in NTSC-based countries for example, there are 30 separate frames displayed every second (1 complete frame every 1/30th of a second)

  14. However, since film is shot at 24 frames per second (1 complete frame displayed every 24th of a second), in order to display film on a typical television screen, the original 24 frames must be converted to 30 frames by a process known as 3:2 pull down.

  15. What Refresh Rate Means • With today's television display technologies, such LCD, Plasma, and DLP(Digital Light Processing), and also disc-based formats, such as Blu-ray Disc. • Refresh rate represents how many times the actual TV, video display, or projected screen image is completely reconstructed every second.

  16. Different Types of Digital TV •  SDTV - Standard definition digital television has the same resolution and 4:3 aspect ratio as traditional analog television but is transmitted in digital fashion. The SDTV picture is 480 x 640 pixels, with interlaced scanning.• EDTV - Enhanced definition television has the same resolution as SDTV but with progressive scanning instead of interlaced scanning, which creates a smoother overall picture. EDTV can be in either the 4:3or 16:9 aspect ratio.

  17. • HDTV (720p) - The first of the three current high definition television formats features 720 x 1280 pixel resolution with progressive scanning. This format is ideal for programming with lots of movement. The aspect ratio is 16:9.• HDTV (1080i). The second current high definition format features greater resolution than 720p (1080 x 1920 pixels), but with interlaced scanning. Like 720p, the aspect ratio is 16:9• HDTV (1080p) - This is the ultimate high definition format, with 1080 x 1920 pixel resolution (in the 16:9 ratio) and progressive scanning. Because of the high bandwidth requirements, this format is not yet used for television broadcasts, although the new HD DVD and Blu-ray high-definition DVD formats will be capable of a 1080p picture.

  18. Ultra-high-definition television also known as Super Hi-Vision or UltraHDincludes 4K UHD (2160p) and 8K UHD (4320p), which are two digital video formats proposed by NHK Science & Technology Research Laboratories and defined and approved by the International Telecommunication Union (ITU). • UHD is a resolution of 2160 × 3840 (8.3 megapixels, aspect ratio 16:9) and is one of the two resolutions of ultra high definition television targeted towards consumer television, the other being 8K UHD which is 4320 × 7680 (33.2 megapixels). UHD has twice the horizontal and vertical resolution of the 1080p HDTV format, with four times as many pixels overall.

  19. Luminance-Chrominance • The luminance-chrominance color model was used to develop an analog color TV transmission system that is backwards compatible with the legacy analog black and white TV systems. • The luminance component, denoted by Y, corresponds to the gray-level representation of video, while the two chrominance components, denoted by U and V for analog video or Cr and Cb for digital video,

  20. It has been observed that the human visual system is less sensitive to variations in chrominance components. • This has resulted in the subsampled chrominance formats, such as 4:2:2 and 4:2:0. • In the 4:2.2 format, the chrominance components are subsampled only in the horizontal direction, • while in 4:2:0 they are subsampled in both directions

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