House video sync is a shared video timing reference distributed around a production or broadcast facility so that connected equipment works from the same reference. It is not timecode, and it does not carry the program’s picture or audio. The rest of this article explains how it works, how it differs from timecode, and where wiring mistakes usually occur.
What house video sync is
House video sync, often shortened to house sync and also called house video reference, is a video timing signal sent through a facility so compatible equipment can align to one common reference. A September 1985 Mix magazine article, archived by World Radio History, describes it in exactly these terms and names composite sync, black burst, and color bars as examples of the signal. Those examples are the same family of references you will still see named in equipment manuals, although newer formats and devices may expect a different reference type, so the manual for your gear is the final authority.
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Why a shared reference matters
Each device with its own internal timing can drift relative to the others. When machines are meant to run together, a common reference keeps their timing from diverging. A documented post-production workflow in the SMPTE Made Simple guide shows timecode generators and machines referenced to a common video signal for this reason. House sync is the reference that makes that alignment possible; it does not, by itself, solve every synchronization problem in a facility.
House sync versus timecode
The two signals are often discussed together, which is why people mix them up. Timecode identifies a position in a program, down to the frame. House sync is a timing reference that equipment locks to. The table below separates the two roles.
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| Question | House video sync | Timecode |
|---|---|---|
| Primary job | Gives connected equipment a shared video timing reference | Labels a position or frame in a program |
| Relationship to devices | Devices are referenced to it | Generators can be referenced to house sync so their output stays aligned with the machines |
| Carries program picture or audio | No; it is a reference, not program content | No; it is a position identifier |
| Typical question it answers | “Are these machines running on the same reference?” | “Which frame is this?” |
Common signal examples
The name covers several reference signals. When you describe a specific installation, state the actual type in use rather than the general term.
Composite sync
The 1985 Mix article lists composite sync as one of the house sync signals. It is a reference signal, not a picture feed, and the distribution rules in the next section apply to it.
Black burst
Black burst is named as a house sync example in the same article and appears in Avid’s installation guide as the reference fed to a synchronization unit. Its use in a given system depends on what the connected equipment accepts.
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Color bars are also listed as an example. Use the term carefully: a color bar signal is a test pattern, and the article presents it as one of the references the house sync name can cover, not as a general-purpose sync signal.
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Termination: the 75-ohm rule in analog routing
The 1985 Mix article is the clearest source for termination in analog house sync routing. It states: “To be used correctly, the video sync signal must terminate in a 75 ohm resistor at the last point on the line.” That guidance describes a legacy analog setup, but it still explains the logic behind most termination questions.
In practice, the signal runs through a chain of devices. Intermediate devices should pass the reference along rather than end it, and the final device, or an external 75-ohm BNC video terminator, provides the end termination. Whether a device passes the signal through depends on whether it has a loop-through output and whether it has a built-in termination switch. A 75-ohm terminator is only needed when the chain actually requires an external end termination; it is not a standard add-on for every setup.
Common routing faults
The Mix article identifies four routing problems that appear repeatedly in analog house sync systems:
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- Multiple termination: more than one device on the line terminates the signal, so the line is loaded at more than one point.
- Early termination: the line is terminated before the last device, so equipment further down the chain does not receive a properly ended reference.
- No termination: the line reaches its last point without the required 75-ohm termination.
- Poor routing: the reference is distributed in a way that does not match the chain’s layout, making termination and loop-through hard to manage.
When a system misbehaves after a change, check these four points before suspecting the equipment itself.
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A device-specific example
Avid’s guide shows one system’s connections: a black burst or house video reference feeds a synchronization unit, a VTR video input (the reference input, where the VTR has one), and an Avid peripheral. This is an example of one system’s wiring, not a universal diagram; another installation may require a different order or different inputs.
Rosendahl’s bonsaiDRIVE manual gives a different kind of example: how a device behaves when it is locked to an external house sync signal. Treat its behavior as specific to that device and do not assume the same lock behavior applies to other hardware.
Checklist before wiring a house sync reference
- Identify the reference type the connected equipment expects, such as composite sync or black burst.
- Confirm which inputs are dedicated reference inputs and which are ordinary video inputs.
- Check whether each device offers loop-through and whether its termination is switchable.
- Make sure exactly one device, at the end of the line, provides the required 75-ohm termination in analog chains.
- Keep the reference feed separate from program video so it is not mistaken for picture content.
Older guides such as the 1985 Mix article describe analog practice. For newer equipment, confirm the reference format, input type, and termination requirements in the current manual for each device.
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