December 16, 2018

TVoT (Television of Things)

Here is a feature of television-related items, and unlike the Internet of Things (IoT), these things has little hype behind them.

A few weeks ago (Novermber 22nd) was the 30th Anniversary of the Max Headroom intrusion on two Chicago television stations. The first intrusion was on WGN (Channel 9). A second intrusion occurred later that evening on WTTW (Channel 11). The original pirate broadcaster was never identified, and subsequent intrusions did not occur.

Shortwave radio carries a television signal! The high-pitched bleeps and buzzes in the background of a short-wave broadcast are actually data streams. Some of these sub-channels carry a series of images rendered at a low frame-rate, which produces a television broadcast of sequentially-scanned still images. This protocol is called slow-scan television (or SSTV) [1], and has its roots in the ham radio community. Modern uses include sending images to earth from the International Space Station [2]. 

If you don't know about mechanical television technology, it's your time to learn. Precursor to the much better-known electronic television, a number of early technologies enabled the reproduction of images by producing horizontal lines within a given image at a certain rate. The higher the scan rate, the faster individual images could be rendered, and the faster new images could replace the complete ones already rendered. Obtaining a higher scan rate meant that the images were more recognizable as a "moving" sequence. 

By and large, m
echanical generation was not commercially successful. Scan rates that would enable high-resolution images were never achieved. The Nipkow disc (invented in 1884) enabled animations based on a sequence of images on a rotating disc visualized using a light source and a Selenium element. The Baird televisor (developed during the 1920s) improved upon the Nipkow disc by transmitting the sequential images using a carrier signal. Like SSTV, there are limited uses for these technologies in the 21rst century, which include Steampunk-themed maker projects, digital light processing, and laser lighting displays (the latter two applications have relied upon significant technical advancements).

Lastly, there was an excellent recent episode of the Function podcast (hosted by Anil Dash) on the history of animated gifs. While it is now a 30-year old technology, animated gif are still an efficient way to present sequential movement and simple animation on the web. While animated gifs have been discussed on this blog in the past, the podcast discussion did mention that the first gif was 1987. So here is an image of the first gif (a flying plane) created by Steve Wilhite [3].

[1] A collection of readings can be found at the National Association for Amateur Radio website.

[2] Trapp C. (2017). Space Technology and Audio Tape to Store Art. Hackaday, December 14. SSTV signals commonly relay images to earth from the space station.

[3] Buck, S. (2012). History of GIFs. Mashable blog, October 19.