Doom-Teletext Crams Id Software's Classic Shooter Into the 1970's Finest TV Data Format

Pseudonymous developer "lukneu" has created a version of Id Software's classic first-person shooter Doom that is unique not for the device on which it runs but in how it renders its video: on an old analog TV as a Teletext page.

"Doom-teletext generates a Teletext stream that contains rendering of the famous first-person shooter game Doom from 1993," lukneu explains of his devilish creation. "The generated data can be piped to applications that process teletext packet streams, either to send it to real TVs or to decode and display teletext pages on a computer. This project is based on the source of doomgeneric, which makes porting Doom quite easy."

Running on a standard PC then transmitting its data across the network to a Raspberry Pi, doom-teletext doesn't display the game on the device's regular video output. Instead, it generates a Teletext stream — a means of sending text and simple graphics using the vertical blanking interval area of a TV broadcast, invisible to the viewer until received and decoded by a TV's built-in Teletext system.

Traditionally, Teletext was used for closed captioning and simple text-based services including news and travel information. Since its launch in 1974, the system was enhanced with support for higher-resolution — but still undeniably-blocky — graphics, but lukneu's creation uses the classic original Teletext format. "Even though higher levels allow for higher resolution graphics and a larger color palette," the developer explains, "this projects generates a stream of level 1 Teletext, mainly because it just feels like 'real' Teletext to me and I like the original blocky look."

The game itself is a largely-unmodified version of Doom with the majority of the original release's features. The graphics, though, are rendered as Teletext "sixels" — equivalent to a display resolution of 78×50, somewhat lower than the DOS version of Doom's 320×200. It's recognizably Doom, though, and surprisingly smooth-running — avoiding the traditional Teletext page selection system's delay by transmitting only a single constantly-updated page, rather than a series of pages one after the other.

"Using a real TV for displaying the Teletext page is great," lukneu notes, "but bear in mind that many modern TVs seem to struggle when updating teletext pages. My LG TV built in 2015 cannot run more than 3(!) FPS [Frames Per Second] smoothly, while my FUNAI tube television handles more than 30 FPS like a champ. If you don't have a suitable TV or Raspberry Pi available, you can also play DOOM in teletext by using a software [emulator] like vbit-iv."

The project's source code and full details are available on lukneu's GitHub repository under the reciprocal GNU General Public License 2. Those with a newer and more powerful Raspberry Pi may find it playable directly on-device, without the need to stream across the network from a traditional desktop, though the developer warns this has yet to be tested.