How to Convert a Camera's HDMI Output to 4K SDI (12G-SDI)

The short answer

To get 4K SDI from a camera that only has HDMI, place an HDMI-to-SDI converter between the camera and the SDI cable. Connect the camera's HDMI output to the converter's HDMI input, then run a coaxial cable with BNC connectors from the converter's SDI output to the SDI device, such as a monitor, switcher, recorder or capture card. For 4K at higher frame rates over a single cable, the converter needs a 12G-SDI output. The camera must also send a clean 4K signal that the converter accepts.

SDI (Serial Digital Interface) is the professional video connection used on broadcast and production equipment. It uses locking BNC connectors and coaxial cable, and it generally runs over longer distances than HDMI. The number in front of SDI (3G, 6G, 12G) describes the data rate of the link. The data rate determines the highest resolution and frame rate that one cable can carry.

Two questions that change the answer

"4K SDI" can describe more than one setup. Answer these two questions before you buy anything.

• Which frame rate do you need? Under the common SDI standards, 12G-SDI carries UHD 4K up to 60 frames per second on one cable. 6G-SDI carries 4K up to 30 frames per second. 3G-SDI is designed for HD up to 1080p60. Some older or high-end systems split 4K across four 3G-SDI cables (quad-link), but for single-cable 4K, 12G is the usual choice.
• Where does the signal end up? If the goal is to feed a computer for a video call or a stream, and the camera sits close to the computer, you may not need SDI. An HDMI capture device can be simpler. SDI makes the most sense when the camera is far from the destination, when the destination only has SDI inputs, or when you want locking connectors.

Link | Typical 4K capability | When it fits

12G-SDI | UHD 4K up to 60p on a single cable | 4K at 50/60p, or future-proofing

6G-SDI | UHD 4K up to 30p on a single cable | 4K at 24/25/30p only

3G-SDI | HD up to 1080p60 (4K only as quad-link) | HD workflows or existing quad-link gear

What you need

• A camera with a clean HDMI output at the resolution and frame rate you want
• An HDMI-to-SDI converter rated for the SDI standard you need (12G for single-cable 4K60)
• A suitable HDMI cable from the camera to the converter, kept short where possible
• Coaxial SDI cable with BNC connectors rated for 12G-SDI if you are running 12G
• Power for the converter, from mains, USB or a battery, depending on the model
• An SDI destination: a monitor, switcher, recorder or SDI capture device

No specific converter models, prices or measured cable lengths were supplied for this guide. Check the manufacturer's datasheet for each converter you are considering. Look for the HDMI input formats it accepts, its SDI output standard, whether it embeds audio, and its maximum cable run.

Step by step

• 1. Check the camera's HDMI output. Look in the manual or menus to see which resolutions and frame rates the camera sends over HDMI. Some cameras record 4K internally but limit HDMI output, or send 4K over HDMI only at certain frame rates.
• 2. Turn on clean output. Disable on-screen overlays such as focus points, battery icons and menus on the HDMI output. Otherwise those graphics appear in the SDI feed.
• 3. Choose a resolution the converter supports. UHD (3840×2160) and DCI 4K (4096×2160) are different formats. Confirm that the converter and the SDI destination both accept the one your camera sends.
• 4. Match the frame rate across the chain. Set the camera, and the destination if it needs this, to the same frame rate. Some switchers and recorders reject signals that don't match their project or system rate.
• 5. Connect HDMI to the converter. Secure the HDMI cable if you can, because HDMI connectors don't lock and loose connections are a common cause of dropouts.
• 6. Run SDI to the destination. Use 12G-rated coax and BNC connectors for 12G signals. Lower-grade cable that works for HD may not hold a 12G signal over the same distance.
• 7. Power on and check for lock. Most converters have status lights that show whether they are receiving a valid input. If yours doesn't, look for the signal at the destination instead.

How to verify the result

Check the signal in stages, because each one can fail separately.

• Signal present: the destination shows a picture and reports the expected format, for example 2160p at your chosen frame rate.
• Clean image: there are no overlays, and the picture has no sparkles, freezes or dropouts. These faults usually point to cable quality, cable length or a loose connection.
• Audio: if you rely on camera audio, confirm that the destination actually receives audio. Seeing that the converter embeds audio is not the same as seeing audio level activity at the destination. Audio level activity is not the same as clear, intelligible sound either, so listen to it.

Using the SDI feed as a webcam for calls

A computer has no SDI input of its own, so you need an SDI capture device that presents the signal to the operating system as a camera. Check that capture device's supported input formats as well. Some capture devices accept 12G-SDI 4K, and others accept only HD.

Even when the capture device appears as a camera, the browser or app still needs camera permission from both the operating system and the browser. Keep these stages separate when you troubleshoot. First, the system has to detect the device. Then the app needs permission to use it, and frames must actually arrive. Finally, call quality depends on the call platform, which may downscale a 4K feed to a lower resolution.

Common problems and limitations

• No picture: the camera may be outputting a format the converter or destination doesn't accept. Try UHD instead of DCI, or a lower frame rate.
• Picture only during playback, or no picture at all: some devices apply copy protection (HDCP) to HDMI. SDI does not carry HDCP, so a protected signal won't convert. Live camera output is often unprotected, but check this if the picture disappears in certain modes.
• Camera shuts off: auto power-off or overheating can end long sessions. Disable auto power-off and use external camera power if it is available.
• 4K looks like HD on a call: this usually comes from the call platform or capture settings, not from the converter.