Video: What you never thought you might want to know
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Video: What you never thought you might want to know

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A quick presentation on video signals, concepts, connectors and modern solutions, given at my workplace for fun.

A quick presentation on video signals, concepts, connectors and modern solutions, given at my workplace for fun.

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Video: What you never thought you might want to know Video: What you never thought you might want to know Presentation Transcript

  • Video: What you never thought you might want to know
    … and some stuff you might actually care about
  • What shall we talk about?
    A little theory
    The video signal
    Picture elements
    Colorspaces
    … and some practice
    Video connectors
    Interlaced vs progressive
    Analog vs digital
  • In theory
    In the beginning was the cathode ray tube…
  • What’s a video signal?
    A stream of images (“frames”) played at a constant rate
    The frame rate must be high enough to fool the human brain into thinking that the motion is continuous (at least 15 frames per second)
  • ... and then?
    Woah, woah, hold up!
    What’s are these “images” you keep mentioning?
    An image is a matrix ofpicture elements, with a specific height and width
    Each of these elements (or “pixels”) has a specific color
  • … and then?
    Since the number of rows and columns is fixed, this is an approximation of the actual image
    The more pixels you fit into a given space, the more accurate the image is and the higher the resolution
  • … and then?
    So a pixel approximates a small sample of the image
    What is a pixel?
    That depends. The value of a pixel depends on the context, but in all cases it represents a color.
  • … and theeeen?
    A color is a vector, and it only has meaning given the correct vector space (or rather, colorspace)
    The common ones are…
    RGB (or sRGB)
    YUV/YPbPr/YCbCr
    CMYK
    HSB/HSV/HSL
    xvYCC
  • and then and then and then and then
  • In practice
    Now comes the stuff you may care about
  • Video connectors
    Legacy connections use analog video signaling:
    Pixels are sent over the wire using an analog encoding scheme
    Horizontal and vertical sync lines signal when a line or frame (respectively) begins and ends
    There are dramatic differences in image quality between systems
  • Analog video connections
    Composite video:
    • 1x RCA connector
    • Multiplexed signal
    • Crappy quality
    S-Video:
    • 4-pin mini-DIN
    • Separate chroma/lumen signals
    • Passable quality
    SCART:
    • Composite, Y/C or RGB video
    • Carries audio
    • Bidirectional
    Interlaced video
  • What’s interlaced video?
    Interlacing was invented to get better image quality out of CRTs with no cost
    The technology is completely obsolete and is one of the worst holdovers from the analog era
    Modern displays require deinterlacingor a progressive signal
  • Modern analog connections
    Component video:
    • YPbPrcolorspace
    • Progressive signal
    • Usually 3x RCA connectors
    VGA connector:
    • D-sub 15 connector
    • Progressive signal
    • RGB + H/V sync
    • DDC data signal
  • A brave new world
    Modern video signals are typically transmitted digitally
    The core concepts have not changed (pixels, colorspaces)…
    … but rather improved and expanded upon:
    New colorspace (xvYCC)
    Consumer Electronics Control (CEC)
    24-bit, 192KHz audio
  • Questions?
    (A)bort (R)etry (I)gnore?
  • To the infinity, and beyond!
    There’s plenty to cover:
    Display technologies
    Measurements and calibration
    Digital video artifacts
    Compression codecs
    What would you like to hear about?...
    tomer@tomergabel.com