SDI vs HDMI: What Is the Difference?

SDI, the serial digital interface, and HDMI, the High-Definition Multimedia Interface, both carry uncompressed digital video and audio from a source to a display, recorder or capture card. They were designed for very different worlds. SDI comes from broadcast: it is standardised by SMPTE, runs over a single 75 ohm coaxial cable and locks in place with a BNC connector. HDMI comes from consumer electronics: it is licensed by HDMI Licensing Administrator, runs over a multi-core cable and uses a push-fit plug.

Those origins explain most of the practical differences. SDI is built for long cable runs, patching and live production, where a dropped connection is not acceptable. HDMI is built for short links between a source and a screen in the same room, with copy protection and features such as device control and return audio.

For edge AI and industrial video, both feed video into a capture card, or into a carrier board with capture built in. The choice usually comes down to distance, vibration and what the camera or source outputs.

The table compares the two interfaces on the points that matter for system design.

HDMI wins on raw bandwidth, so it carries 8K and high-refresh formats that SDI does not. SDI wins on distance, locking connectors and the broadcast features engineers rely on, such as timecode and many audio channels.

Cable length is usually the deciding factor. Passive HDMI cables are reliable to roughly 10 to 15 m at 1080p and often only a few metres at 4K. Beyond that, HDMI needs active cables, fibre HDMI cables or extenders over Ethernet. SDI over good 75 ohm coax runs around 100 m at 3G-SDI and still tens of metres at 12G-SDI, with no extra hardware. Our BNC connector FAQ gives typical runs for each SDI generation and the cable to use.

Where HDMI sources must reach further, SDI and HDMI converters turn the signal into SDI for the long run and back again at the far end, and video extenders carry HDMI over twisted pair or fibre.

Both interfaces are uncompressed, so neither adds meaningful delay on its own: the latency in a video system comes from processing, encoding and display, not from the cable. The differences show up elsewhere. HDMI uses a two-way link, with a handshake for EDID and HDCP, so a source can refuse to send video or fall back to a lower resolution if the handshake fails. SDI is one-way: the source transmits and any receiver on the cable can lock to it, which makes splitting, looping through monitors and patching straightforward. That simplicity is a large part of why broadcast and defence systems still standardise on SDI.

SDI is preferred where cameras are far from the computer, or where vibration could loosen a connector, such as on vehicles, aircraft and gimbals. HDMI is simpler and cheaper where equipment sits close together.

On an edge computer, the capture card is where SDI or HDMI video becomes data an AI model can use. The points to check are the number of inputs, the formats each input accepts, whether the card supports the operating system and AI framework on the computer, and whether it captures straight into GPU memory to keep latency low.

Our SDI capture cards range from single 3G-SDI inputs to 12G-SDI cards for 4K60, and our HDMI capture cards cover HDMI 2.0 and 2.1 sources. Our guide to SDI capture for edge AI explains how those inputs feed an inference pipeline, and the fanless GPU computer case study added 3G-SDI capture to a custom Jetson carrier board.

We fit SDI and HDMI capture cards in industrial and edge AI computers as standard, install the drivers and validate each input before the system ships.