TVI vs AHD vs CVI vs CVBS: How to Identify Your Security Camera's Video Format

Two security cameras can use the same coax cable, the same BNC connector, and look almost identical on the outside — and still send completely different video signals.

That's because most coax-based security cameras today use one of four video formats: HD-TVI, AHD, HD-CVI, or CVBS. If the camera's format doesn't match what the DVR or monitor can read, you won't get a proper picture, even though every cable is connected correctly.

Here's what each format is, how to tell which one your camera uses, and how to avoid format problems on your next install.

The Four Formats at a Glance

Format What It Is Resolution
CVBS Traditional analog composite video, used by older CCTV cameras (often listed as 700TVL, 800TVL, 1000TVL or 960H) Standard definition
HD-TVI HD-over-coax format developed by Techpoint 720p and up; newer versions support 4K
AHD HD-over-coax format developed by Nextchip 720p and up; newer versions support 4K
HD-CVI HD-over-coax format developed by Dahua 720p and up; newer versions support 4K

All four travel over the same type of coax cable with BNC connectors. That's what makes HD-over-coax so useful for upgrading an older analog system: in many buildings, the existing cable can stay in place.

But the signals themselves are encoded differently. A recorder or monitor that only understands one format will not correctly decode the others.

What a Format Mismatch Looks Like

When a camera's format doesn't match the device it's connected to, you'll typically see one of these symptoms:

  • No video at all, or a "No Signal" message
  • A black-and-white image that rolls or scrolls vertically
  • Distorted colors or a picture split into repeating strips
  • A picture that appears, but at a much lower resolution than expected

These symptoms are easy to mistake for a bad cable, a failed camera, or a power problem. Before replacing anything, check the video format first.

How to Identify Your Camera's Format

1. Check the label or model number

Many cameras list the format on the label, the box, or in the model name. Terms like "TVI," "AHD," "CVI," or "4-in-1" are usually printed somewhere on the product or its spec sheet.

2. Look at the resolution rating

If a camera is rated in TV lines (TVL) rather than megapixels or 1080p, it's almost certainly a CVBS analog camera.

3. Check whether the camera is 4-in-1

Many modern coax cameras are 4-in-1, meaning they can output TVI, AHD, CVI, or CVBS. Only one format is active at a time. Depending on the model, the output is usually switched by:

  • A small joystick or button on the camera's cable pigtail
  • A DIP switch inside the camera housing
  • The camera's on-screen (OSD) menu
  • Coax control commands sent from a compatible DVR

Always check the camera's manual for its default format and the exact switching method. A 4-in-1 camera that shows a rolling black-and-white image is often simply set to a different format than the recorder expects.

4. Test it directly

On a job site, the fastest way to confirm a camera's format is to connect it to a CCTV tester or a multi-format BNC monitor. Many testers display the detected format and resolution on screen, which removes the guesswork before the camera goes up on the wall.

Mixed-Format Systems: Where Most Problems Start

Few real-world systems are built all at once. A typical building might have a few older analog cameras, some 1080p cameras added a few years later, and new 5MP cameras from a different brand.

That's where format compatibility on the recorder and monitor side matters most.

Quick Format Checklist Before You Install

  1. Camera format: TVI, AHD, CVI, CVBS, or switchable 4-in-1?
  2. Camera resolution: 1080p, 5MP, 4K, or TVL-rated analog?
  3. Recorder support: Does the DVR accept that format at that resolution?
  4. Monitor support: If connecting directly, does the monitor's BNC input support the same format and resolution?
  5. Mixed system: Will you need a hybrid DVR or multi-format monitor to handle more than one format?

The Bottom Line

The coax cable and BNC connector tell you how the video travels. They don't tell you what format the video is in.

Checking the format first — on the camera, the recorder, and the monitor — can turn a frustrating "no picture" troubleshooting session into a two-minute fix.

Working with a mixed or upgraded coax system? Browse SecurityVideoDirect's 4-in-1 security cameras, hybrid DVRs, and multi-format monitors built for HD-over-coax installations.

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