Does the OSSC Output DVI or HDMI?

The Open Source Scan Converter (OSSC) uses a physical HDMI connector on modern revisions, but whether it outputs a native DVI or HDMI digital signal depends entirely on user configuration and hardware version. While early hardware revisions featured a physical DVI connector, modern versions carry an HDMI port that defaults to transmitting a DVI-compatible video signal. This article explains the technical differences between these output modes, the hardware capabilities of the OSSC, and how to configure the device for optimal display compatibility.

Physical Connector Differences by Hardware Revision

The physical video output on the OSSC depends on the hardware version:

  • OSSC Version 1.5: Features a physical DVI-D output connector. It outputs pure DVI-D digital video and cannot natively carry embedded audio without external hardware modifications.
  • OSSC Version 1.6 and Later: Replaced the DVI connector with a standard full-sized HDMI Type-A connector. Despite the change to an HDMI port, the underlying signal type is selectable in software.

Native DVI Mode vs. Native HDMI Mode

The digital video signals used by single-link DVI and HDMI are electrically identical (both use Transition-Minimized Differential Signaling, or TMDS). However, the protocol framing and metadata differ:

  • DVI Mode: Transmits pure uncompressed digital video data (RGB 4:4:4). DVI mode does not carry audio packets, InfoFrames, or consumer electronics control (CEC) data. Because it lacks complex HDMI handshakes and audio streams, DVI mode provides the highest compatibility with computer monitors and legacy digital displays.
  • HDMI Mode: Packages the video signal alongside embedded digital audio packets and CEA-861 InfoFrames. In this mode, the OSSC digitizes analog audio inputs (via the 3.5mm AV inputs or SCART connector) and embeds the audio directly into the digital video stream, allowing sound to play through modern TV speakers or AV receivers without extra cables.

Default Behavior and Firmware Configuration

On hardware revision 1.6 and later, the OSSC firmware typically defaults to DVI mode, even though it utilizes a physical HDMI port. This default prevents audio transmission errors and handshaking issues on displays that are sensitive to non-standard retro refresh rates (such as 59.7 Hz from an SNES or 59.2 Hz from an Neo Geo).

To switch between native DVI and native HDMI output:

  1. Press the Menu button on the OSSC remote.
  2. Navigate to Audio & sync opt.
  3. Locate the DVI/HDMI mode (or Output mode) setting.
  4. Toggle the setting from DVI to HDMI.

When to Use Each Mode

  • Use HDMI Mode if you are connecting the OSSC directly to a modern television, home theater receiver, or capture card, and you want video and audio delivered through a single HDMI cable.
  • Use DVI Mode if your television or PC monitor displays a "No Signal" or "Out of Range" error in HDMI mode, or if you use an external sound system and only need the digital output strictly for video.