Lip-Sync and Timecode Mistakes That Keep Coming Back, and How to Avoid Them

Why sync problems are rarely one fault

When a presenter's lips drift away from their voice, the first instinct is to blame the microphone or the mixer. In most studios I visit the cause is a chain of small delays that nobody measured, each harmless on its own. A digital mixer adds a few milliseconds, a frame synchroniser adds a frame, a graphics system adds another, and the monitor in the gallery adds its own lag on top.

The mistake is treating the symptom at the end of the chain. Someone nudges a delay setting on the playout feed until it looks right on one monitor, and the problem seems solved. It returns the next time a source changes, because the correction was tuned to a single path rather than to the whole signal flow.

Before touching any setting, write down every device the sound and picture each pass through, in order. It is dull work, but it usually shows within minutes where the two paths part company.

• Draw the audio and video paths side by side
• Note every converter, mixer and processor on each path
• Mark which devices add a fixed delay and which vary

Judging sync by eye on a single monitor

Checking lip-sync by watching a face on one screen is the habit I would most like to retire. Monitors differ in how long they take to draw a picture, particularly those with motion smoothing or heavy image processing switched on. A screen that lags by two or three frames will make perfectly aligned material look early in the audio.

Ears and eyes also adapt. After twenty minutes in a gallery you stop noticing a small offset, while a viewer who has just tuned in notices it at once. Relying on whoever happens to be in the room is therefore an unreliable test, however experienced they are.

Use a proper reference instead: a clapper or a flash-and-beep test signal sent through the real chain, then measured on a waveform and picture display that you trust. Switch off processing on the monitor you use for judging, or check its stated latency. A measured number can be written down and compared next month; a feeling cannot.

Ignoring timecode until something has to be edited

Timecode is often set up once, years ago, and then trusted without question. The common mistake is running different devices on free-running clocks that were set by hand. They agree on the day of installation and part company slowly, so a recording from the camera and one from the audio recorder no longer line up when they reach the edit.

A second error is mixing frame rates without noting it. Drop-frame and non-drop-frame counts look nearly identical on a display, yet over a long recording they diverge by a measurable amount. The problem is found late, when a programme runs a few seconds longer than the schedule allows.

Choose one master clock for the studio and feed it to everything that needs it. Agree the frame rate and counting method in writing, and put the setting on a label near the equipment. When a visiting crew brings its own gear, jam-sync it to your master at the start of the day and check it again after lunch.

• One master clock, distributed to every recorder
• Frame rate and drop-frame setting recorded on paper
• Re-check visiting equipment during the day

Fixing delay by adding more delay

A frequent shortcut is to hold the audio back by whatever amount makes the picture and sound agree, then move on. It works for the moment, but the delay becomes part of the studio folklore: nobody remembers why a mixer output is set to forty milliseconds, and the next engineer either removes it or copies it somewhere it does not belong.

The harm shows when the studio feeds more than one destination. Studio speakers, a stream, a recording and a remote contributor all sit at different points in the chain, and a delay tuned for one of them spoils another. Talkback and foldback are hit hardest, because performers hear themselves late and start to rush or hesitate.

Treat compensating delay as a documented setting, not a quick repair. Record where it sits, how large it is, which signal it applies to and why it was needed. Where possible, remove the cause, for example a needless conversion, rather than covering it. Then each output gets the correction that suits it.

Changing the setup without testing it again

Studios are rarely static. A new camera arrives, a mixer firmware update is installed, a playout machine is replaced, or a guest joins by a remote link. Each change can move the timing of one path against another, and the common mistake is assuming that because the previous test passed, the system is still aligned.

Remote contributors deserve special care. Their sound arrives with the network delay of the moment, and the return feed they hear is delayed again. Expecting them to speak naturally while hearing themselves a quarter of a second late is unrealistic. A clean-feed return, or a mix-minus arrangement agreed beforehand, saves a good deal of frustration on air.

Build a short alignment check into every change, and into the start of each production day. It takes ten minutes with a test signal and a note pad. Keep the results in a log, dated and initialled, so that a drift of a frame or two is spotted as a trend, not discovered during a live programme.

• Test after any firmware update or equipment swap
• Agree a mix-minus return for remote guests
• Keep a dated alignment log beside the desk

Leaving the knowledge with one person

In many small studios one engineer understands the timing of the whole building. They know which mixer channel needs a nudge and which monitor lies. It works until they are on leave, and then a minor fault becomes a long afternoon of guesswork on live air.

The mistake is not the reliance on a skilled person, but the absence of anything written down. A single page showing the signal path, the master clock, the measured delays and the test procedure lets a colleague take over calmly. It also makes it far easier for an outside adviser to see the system quickly, which shortens any review.

Ask the whole crew to run the alignment check at least once, so that it stops being a private ritual. People notice faults sooner when they know what correct looks like. Keep the page short, update it when equipment changes, and store a printed copy where the control room staff can reach it.