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Chapter Five Fundamental Concepts in Video. In the recent lecture: Types of Video Signals Analog Video Digital Video. Three Video Market Segment. Types of Video Signals. Component Video: 3 Separate wires: luminance + 2 color difference Signals (Y, P B , P R ),

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Chapter Five Fundamental Concepts in Video

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Chapter five fundamental concepts in video

Chapter Five

Fundamental Concepts in Video


Chapter five fundamental concepts in video

In the recent lecture:

  • Types of Video Signals

  • Analog Video

  • Digital Video


Chapter five fundamental concepts in video

Three Video Market Segment


Chapter five fundamental concepts in video

Types of Video Signals

Component Video:

  • 3 Separate wires: luminance + 2 color difference

    Signals (Y, PB, PR),

    PB=R-Y, PR=B-Y

  • Used in most Computer Systems

    SVGA (Super Video Graphics Array) is one of the best and most widely used video signal types

    • The primaries can either be RGB or a luminance-chrominance transformation of them (e.g., YIQ, YUV).

    • Best color reproduction

    • Requires more bandwidth and good synchronization of the three components


Chapter five fundamental concepts in video

Types of Video Signals

Composite Video:

  • Video-only components of for one channel on one wire

  • color (chrominance) and luminance signals are mixed

    into a single carrier wave.

  • Some interference between the two signals is inevitable.

  • Used in NTSC (YIQ)


Chapter five fundamental concepts in video

Types of Video Signals

S-Video:

  • Separated video --- a compromise between component analog video and the composite video.

  • It uses two lines, one for luminance and another for composite chrominance signal.

  • Used in S-VHS


Chapter five fundamental concepts in video

Types of Video Signals

Composite Video Component Video

  • Component Video is native format for digital TV since MPEG compression operates on component video

  • Component video does away with several artifacts of composite video


Chapter five fundamental concepts in video

Analog Video

Analog videoAnalog means that the video signal is transmitted by a high-frequency wave. Changing the wave's amplitude represents the different colors shown on the screen. Analog video is found in most older computer video displays, as it is the original standard to transmit video over coaxial lines.

Digital videoDigital means that the video signal is transmitted in ones and zeros. The transmission sends a very fast stream of data about each and every pixel on the screen.


Chapter five fundamental concepts in video

Analog Video

Deflection coil: magnetically steers beam in a left-to-right top-to-bottom

excited by electron beam, intensity of beam determines brightness


Scanning methods display modes

Analog Video

Scanning Methods (Display Modes)

Interlaced

  • odd lines are displayed first, then even lines

  • Taken together, all the odd lines are called a field (and similarly for all the even lines).

  • The original purpose of interlaced display was to avoid flicker.

  • Standard television uses this method, displaying 60 fields per second (which makes 30 frames per second).

  • Half Band width required.


Scanning methods display modes1

Scanning Methods (Display Modes)

Analog Video

Progressive

  • The method used by computer monitors.

  • An entire screen can be written to a buffer.

  • The buffer is displayed “instantaneously.”


Scanning methods display modes2

Analog Video

Scanning Methods(Display Modes)


Chapter five fundamental concepts in video

Analog Video

17


Chapter five fundamental concepts in video

Active

Analog Video

Scanning Methods(Display Modes)


Chapter five fundamental concepts in video

Analog Video:Representation

NTSC Video

�National Television Systems Committee

� 525 scan lines per frame, 30 (29.97)fps (33.37 µsec/frame).

� Interlaced, each frame is divided into 2 fields, 262.5 lines/field, , 4:3 aspect ratio.

� 20 lines reserved for control information at the beginning of each field

� So a maximum of 485 lines of visible data

• Laserdisc and S-VHS have actual resolution of ~420 lines

• Ordinary TV --~320 lines • Each line takes 63.5 microseconds to scan.

� Color representation:

• Uses YIQ color model.


Chapter five fundamental concepts in video

Analog Video: Decoding NTSC

  • Cheapest method: low pass filter with 3MHz cutoff to get rid of chroma

    • But also removes some of the high frequency luminance data, and blurs the image

  • If some color signal remains in the recovered Y values, it will look like dots crawling up vertical edges – “chroma crawl”

  • If some luminance signal remains in the separated chroma values, it will appear that rainbows are superimposed on what should be monochrome


Chapter five fundamental concepts in video

Analog Video:Representation

PAL (SECAM) Video

� Phase Alternating Line

� 625 scan lines per frame, 25 frames per second, , 4:3 aspect ratio (40 µsec/frame)

� Interlaced, each frame is divided into 2 fields, 312.5 lines/field

� Color representation:

  • Uses YUV color model


Chapter five fundamental concepts in video

Analog Video:Representation

SECAM

�Système Electronique Couleur Avec Mémoire

�625 scan lines per frame, 25 frames/s, 4:3 aspect ratio

�R-Y and B-Y information is transmitted (sequentially) in alternate lines, and a video line store is used to combine the signals together  the vertical color resolution is halved relative to PAL and NTSC

� differs from PAL in the color coding scheme

� Color representation: Uses YUV color model


Summary standards organizations for video originally analog extended to digital

SummaryStandards Organizations for Video (originally analog, extended to digital)

Analog Video


Chapter five fundamental concepts in video

Analog Video

24


Chapter five fundamental concepts in video

Digital Video

  • Digital video signal consists of luminance and chrominance information

  • Luminance – brightness, varying from white to black (abbreviated as Y)

  • Chrominance – color (hue & saturation), conveyed as a pair of color difference signals:

    • R-Y (hue & saturation for red, without luminance)

    • B-Y (hue & saturation for blue, without luminance)

    • Where’s the green?


Chapter five fundamental concepts in video

Digital Video: sampling


Chapter five fundamental concepts in video

Digital Video: sampling

4:2:0 sampling

4:2:2 sampling

4:1:1 sampling

4:2:2 – High End DV

4:2:0 – MPEG 1 & 2

4:1:1 – DV and DVCAM


Chapter five fundamental concepts in video

Digital Video: sampling

Why not 4:4:4 sampling?

  • 720 x 486 resolution = 349,920 pixels per frame

  • 349,920 pixels x 10 bits/sample x 3 samples/pixel = 10,497,600 bits per frame

  • 10,497,600 bits/frame X 29.97 frames/second = 314,613,072 bits per second

  • 314,613,072 bps x 3600 seconds = ~141.58 GB/hour

  • For 1920x1080 HDTV, more like 840 GB/hour

  • 4:2:2 sampling drops that rate by a third ? with almost no perceptible difference in quality.

  • 4:2:0 and 4:1:1 drop it in half ?

    • about 70 GB/hour for normal resolution video


  • Chapter five fundamental concepts in video

    Resampling:

    Resampling by interpolation is generally understood as the following procedure:

    • Prepare Original sample values.

    • Create new empty array with new dimensions using a proper geometric transformation method.

    • Interpolate new sample values of the above array (in 2) using sample values from original array (in 1).

    • Step 3 can performed using a suitable interpolation function.

      This can summarized in following equation:


    Chapter five fundamental concepts in video

    Resampling:

    Original coordinate of the original sample array

    Original sample value

    boundary

    of the function

    (kernel size)

    New coordinate of interpolated sample array

    kernel size

    interpolation function

    Interpolation sample value

    Fx calculated as follow:

    Fx = x × kx (Exact position (floating-point number))

    x1 = Integer (Fx) ( Integer position (integer part of number))

    Fx = Fx - x1 ( Fraction part of number (integer+fraction=exact))

    kx represent magnification ratio


    Chapter five fundamental concepts in video

    Resampling:

    Digital Interpolation methods

    • Interpolation is a technique that pervades many an image application.

    • Let us ask why digital image interpolation?

    • To insert between or among others.

    • To change by putting in new configuration.

    • Image restoration by estimating a missing value by taking an average of known values at neighboring points.

    • For these reason, some of these interpolation methods will be cleared


    Chapter five fundamental concepts in video

    Resampling:

    Digital Interpolation methods

    Nearest-Neighbor Interpolation method

    • Nearest-neighbor interpolation method can summarized as follow:

    • Set the intensity of the interpolated pixel to the nearest-neighbor original pixel.

    • This method is very fast, but it produces aliasing or blocking effects along edges.

    • The function can be described by

    factor multiplied by the nearest pixel value

    (function kernel)


    Chapter five fundamental concepts in video

    Resampling:

    Digital image Interpolation example

    33


    Converting analog video to digital ccir standards for digital video

    Digital Video

    Converting Analog Video to DigitalCCIR Standards for Digital Video

    • CCIR 601 (one standard for digital video) specifies a standard that applies to both NTSC and PAL.

    • According to the CCIR standard, a frame is sampled to 720 X 480 pixels for NTSC and 720 X 576 for PAL.

    • But this is misleading. There aren’t really 720 pixels per line. The number of samples taken to digitize the video doesn’t necessarily correspond to the number of pixels on the display device.

    • You can do digital video in NTSC format at 640 X 480 or 720 X 480 with different pixel aspect ratios.

    • You can do digital video in PAL format at 720 X 480 or 720 X 576 with different pixel aspect ratios.


    Converting analog video to digital ccir standards for digital video sub sampling

    Digital Video

    Converting Analog Video to DigitalCCIR Standards for Digital VideoSub-Sampling

    • CCIR 601 prescribes 4:2:2 sub-sampling of the chrominance component.

    • This means that there in every 4-pixel-square area, 4 luminance samples are taken and 2 of each of the chrominance samples are taken (4 Y’ samples, 2 CB samples, and 2 CR samples).


    H 261

    Digital Video

    H.261

    Converting Analog Video to DigitalCCIR Standards for Digital VideoSub-Sampling

    • Real time constrain

      • Video conference cannot tolerate longer delays without becoming disjointed.

      • Maximum delay: 150 ms (about 7 frames/sec)

    • Picture format

      • CIF (Common Intermediate Format)

        • Component(size): Y(352  288), Cb & Cr(176  144)

        • Picture rate: 29.97 frames/sec

      • QCIF (Quarter CIF)

        • Component(size): Y(176  144), Cb & Cr(88  72)


    Video format

    Video format

    Digital Video

    Picture format

    QCIF: Mobile video communication

    CIF:Videoconference

    CCIR: Standard Definition TV

    ATSC: High Definition TV


    Video formats

    Digital Video

    Video formats


    Why hdtv

    Why HDTV?

    Digital Video

    HDTV (High Definition TV)

    • Higher-resolution picture

    • Wider picture

    • Additional data

    • Easy to interface with computers


    Digital television sdtv hdtv

    Digital Television: SDTV, HDTV

    Digital Video

    HDTV (High Definition TV)

    • SDTV vs. HDTV

      • Standard definition television

      • High definition television

    • Is HDTV the same thing as digital TV?

      • No

    • Characteristics of HDTV

      • 16:9 aspect ratio (1280 X 720 or 1920 X 1080)


    Hdtv vs dtv

    Digital Video

    HDTV vs. DTV

    • High definition television is not necessarily digital – that is, it does not have to be digitally transmitted.

    • What characterizes HDTV is the aspect ratio, resolution, and sound quality

    • Digital television is not necessarily HDTV.

    • What characterizes DTV is the way in which the data is transmitted – in digital, as opposed to analog, form.

    • HDTV was not originally DTV, but at present most HDTV is digitally transmitted.


    Hdtv vs dtv1

    Digital Video

    HDTV vs. DTV

    • There are 18 different DTV formats

    • 6 are also HDTV.

    • 5 of these (the DTV formats that are also HDTV) are based on progressive scanning and one 1 interlaced.

    • Both HDTV and DTV use MPEG-2

    • Three of the 18 formats for DTV that are used frequently are:

      • 480p – 640 X 480 pixels, progressive

      • 720p – 1280 X 720 pixels, progressive

      • 1080i – 1920 X 1080 pixels, interlaced, why?


    Components of hdtv systems

    Components of HDTV systems

    Display

    format

    Decoded

    video

    signals

    analog

    carrier

    +

    digital

    signals

    video

    signals

    Image

    Decoder

    Display

    Processor

    digital

    signals

    Demodulator

    De-multiplexer

    Audio

    Decoder

    Decoded

    audio

    signals

    audio

    signals


    Comparison

    Comparison

    Current TV

    HDTV


    Comparison current tv

    Comparison (current TV)


    Comparison hdtv

    Comparison (HDTV)


    Chapter five fundamental concepts in video

    Typical Video System Chain


    Chapter five fundamental concepts in video

    Typical Video System Chain


    Chapter five fundamental concepts in video

    Typical Video System Chain


    Chapter five fundamental concepts in video

    Typical Video System Chain


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