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# Composite video

Before dedicated RGB monitors became common in the late 1980s, many home PC users connected their computers to TVs or composite video monitors. The NTSC composite signal introduces interference patterns that produce unexpected colours — a phenomenon known as artifact colours — expanding CGA’s usual 4-colour palette to as many as 16. It sounds like a bug, but developers deliberately exploited it.

CGA’s two graphics modes — 320×200 medium resolution and 640×200 high resolution — both produce artifact colours on a composite display, though the higher-resolution mode yields a broader and more distinct palette, and was the more popular choice for games built around composite output. Counterintuitively, 640×200 is a monochrome mode — it outputs only black and white pixels — but it’s precisely that high-frequency alternating pattern that the composite signal smears into colour.

Composite emulation is available for the CGA, IBM PCjr, and Tandy 1000 machine types.

## Composite support in games

Sierra On-Line was particularly enthusiastic adopters: games like King’s Quest and Space Quest would prompt you at startup to choose between RGB and composite modes, with the composite graphics being the more colourful and detailed of the two. On RGB without that mode selected, they appear as garish 4-colour affairs. Earlier titles like Microsoft Decathlon and Ultima II : Revenge of the Enchantress used composite colour from the outset, without bothering to offer an RGB fallback at all.

DOSBox Staging automatically enables composite emulation when a game switches to the 640×200 composite mode. For the more common 320×200 modes, you’ll need to enable the composite setting manually.

Notable games with composite video support

See the linked Google Spreadsheet in this blog post for a complete list.

- Ancient Art of War, The (1984)
- Bard’s Tale II: The Destiny Knight, The (1986)
- Below the Root (1984)
- Black Cauldron, The (1986)
- Bruce Lee (1985)
- California Games (1987)
- Demon’s Forge (1987)
- Donald Duck’s Playground (1986)
- Dragon Wars (1990)
- Gold Rush! (1988)
- Jumpman (1984)
- King’s Quest (1984)
- King’s Quest II (1985)
- Leisure Suit Larry (1987)
- Maniac Mansion (1987) (CGA version)
- Microsoft Decathlon (1982)
- Mixed-Up Mother Goose (1987)
- Pitstop II (1984)
- Seven Cities of Gold, The (1985)
- Space Quest (1986)
- Transylvania (1986)
- Ultima II : Revenge of the Enchantress (1983)
- Ultima III: Exodus (1985)
- Where in the U.S.A. is Carmen Sandiego? (1986)
- Zak McKracken and the Alien Mindbenders (1988) (CGA version)

## Tuning the composite colours

Artifact colours are sensitive to the phase of the composite signal, which means the hue can drift between different cards and setups. Real NTSC monitors had a physical tint dial for exactly this reason, and IBM even included a “COLOR ADJUST” trimpot on the PC motherboard to compensate. The hue setting lets you replicate that adjustment — if colours look off, this is the first thing to tweak. Adjust the hue setting for each game until the colours look as expected (e.g., blue skies, green grass).

Early and late CGA card revisions produce slightly different artifact patterns, and some games were designed with one revision in mind. The era setting lets you choose which to emulate.

## Configuration settings

You can set the CGA composite video parameters in the `[composite]` configuration section. CGA composite monitor emulation is only available for `cga`, `pcjr`, and `tandy` machine types.

##### composite

  Enable CGA composite monitor emulation. This allows the emulation of NTSC artifact colours from the raw CGA RGBI image data, just like on a real NTSC CGA composite monitor.

  Possible values:

  - `auto` default – Automatically enable composite emulation for the 640x400 composite mode if the game uses it. You need to enable composite mode manually for the 320x200 mode.
  - `on` – Enable composite emulation in all video modes.
  - `off` – Disable composite emulation.

  Note

  Fine-tune the composite emulation settings (e.g., hue) using the composite hotkeys, then copy the new settings from the logs into your config.

##### era

  Era of CGA composite monitor to emulate.

  Possible values:

  - `auto` default – PCjr uses `new`, and CGA/Tandy use `old`.
  - `old` – Emulate an early NTSC IBM CGA composite monitor model.
  - `new` – Emulate a late NTSC IBM CGA composite monitor model.

##### hue

  Set the hue of the CGA composite colours (`0` by default). Valid range is -360 to 360. For example, adjust until the sky appears blue and the grass green in the game. This emulates the tint knob of CGA composite monitors which often had to be adjusted for each game.

##### convergence

  Set the sharpness of the CGA composite image (`0` by default). Valid range is -50 to 50.