This document provides an overview of key concepts in video technology, including the video signal, picture elements (pixels), colorspaces, video connectors, interlaced vs progressive formats, and analog vs digital video. It discusses the history of video starting with cathode ray tubes and how video signals transmit a stream of images (frames) at a constant rate. Pixels make up each image and can have different color values depending on the colorspace. The document contrasts legacy analog video connections with modern digital formats and covers related topics like display technologies.

1. Video: What you never thought you might want to know … and some stuff you might actually care about

2. 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

3. In theory In the beginning was the cathode ray tube…

4. 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)

5. ... 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

6. … 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

7. … 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.

8. … 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

9. and then and then and then and then

10. In practice Now comes the stuff you may care about

11. 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

13. Multiplexed signal

15. Separate chroma/lumen signals

17. Carries audio

18. BidirectionalInterlaced video

19. 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

21. Progressive signal

23. Progressive signal

24. RGB + H/V sync

26. Questions? (A)bort (R)etry (I)gnore?

27. 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