Dreamcast:Video Output

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The Dreamcast natively supports 240p, 480i, and 480p resolutions.[1] All Dreamcast games support 480i, many support 480p, and a few support 240p. The Dreamcast is capable of outputting Composite, S-Video, VGA, RGB, and Component video.

HDMI Plug-and-Play Options

Unbranded Cables

Most of the unbranded plug-and-play HDMI cables the Dreamcast aren't compatible with any 480i/240p game. Some have a very soft output, and others barely work at all. They don't seem to add lag.

Beharbros Analog to Digital Converters

The Gekko and Akura by Beharbros [2] are analog to digital converters.

Both the Gekko and Akura output 480p over HDMI, and the quality of the image and latency may vary depending on how well the connected display upscales the image to the display's native resolution. All VGA analog to digital converters will not correct the aspect ratio and sampling issues.

Gekko

The Gekko specs includes features 480p output from HDMI, a 15khz RGB/31khz VGA mode switch, and stereo. [3] The manufacture does not guarantee that all non VGA games will work.

Akura

The Akura Analog to Digital Converter offers the all the same features as the Gekko with the added functionality of configurable scanlines. [4]

VGA

The VGA output of the Dreamcast is 480p, but it is not the "typical" 480p DTV resolution (720 x 480) of televisions. The VGA output of the Dreamcast is 480p VESA resolution (640 x 480) within a 480p DTV signal.[5]

This means that the correct sample rate of the Dreamcast 480p signal is 858 pixels per line, the same sample rate of any 480p DTV signal.[6] If the signal is interpreted as VESA only 800 pixels per line will be sampled, and at this sample rate 43 pixels columns will be lost within the active picture area. Also, if sampled at 800 pixels per line neighboring columns get blurry since the 43 columns are evenly distributed across the screen.

References

  1. (5/12/2022) Sega Dreamcast. https://www.retrorgb.com/dreamcast.html
  2. (5/12/2022) BeharBros Home Page. http://www.beharbros.com/
  3. (5/12/2022) Gekko Product Page. https://www.beharbros.com/gekko
  4. (5/12/2022) Akura Product Page. https://www.beharbros.com/akura
  5. The 480p VESA is a standard resolution of PC monitors native to the era the Dreamcast was manufactured.
  6. http://pms.hazard-city.de/ossc_sampling.jpg