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.

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Video: What you never thought you might want to know

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