Last Updated 2 days ago
Filmmaking Dictionary: Number 3 / 3G-SDI
Definition
3G-SDI is a serial digital video interface with a nominal data rate of about 3 gigabits per second, commonly 2.97 Gb/s. It is used to carry professional digital video and associated data over an appropriate SDI connection.
The ‘3G’ identifies a bandwidth class. It is not mobile-phone service, a 3K image resolution or a guarantee that every signal with an SDI connector will work.
Common Uses
A familiar application is carrying 1080-line progressive HD at rates up to 50 or 60 frames per second, subject to the equipment’s supported formats. Cameras, monitors, switchers, converters and recorders must agree on the actual signal.
Some devices use the available bandwidth for different sampling or transport arrangements. Read the supported-format list rather than assuming that any device labelled 3G-SDI accepts every possible 3G mapping.
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Level A and Level B
3G-SDI includes different mapping arrangements commonly described as Level A and Level B. A transmitter and receiver that do not support the same arrangement can fail to communicate even though their connectors and nominal bandwidth appear to match.
For example, a camera can send a valid 1080p signal while an older monitor remains blank because it does not accept the selected mapping. Changing resolution at random may conceal the real issue. Check the output format and the receiver’s supported settings first.
Cable and Signal Path
Use suitable 75-ohm video cable and connectors rated for the required signal and distance. Cable construction, length, damage, adapters and patch points all affect the usable margin. There is no single maximum cable length that applies to every 3G-SDI setup.
A path may work at a lower data rate and fail when the camera switches to a higher-bandwidth output. Test the entire route, including converters and distribution equipment, in the exact mode needed for the shoot.
Troubleshooting Checks
- Confirm resolution, frame rate and progressive or interlaced output.
- Check Level A/B support on both ends.
- Use a known-good cable to isolate the signal path.
- Inspect adapters, barrels and patch connections.
- Verify that embedded audio and ancillary data meet the workflow’s needs.
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Frequently Asked Questions
Does a BNC connector guarantee 3G-SDI support?
No. The connector shape does not establish the electronics’ capabilities or the cable’s rating.
Is 3G-SDI automatically a single-cable UHD connection?
No. Common UHD workflows require higher bandwidth or multiple links, depending on format.
Related Terms
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