Before You Commission an Audio Sync Audit: A Checklist
Priya Patel
7 min read
A practical list of what to gather, check and decide before asking for an audit of lip-sync, latency and clocking across your audio and video chain.
Start with what the viewer actually sees
Most audit requests begin with a complaint: a presenter whose mouth seems to arrive before or after the voice, or a remote guest who always sounds slightly behind. Before anything else, write down where and when the problem appears. Does it show on the programme output, on one monitor in the gallery, on a recording only, or on the stream? Does it come and go, or sit at a steady offset?
A steady offset usually points to a fixed delay somewhere in the chain, such as a frame synchroniser, a scaler or a processing stage that adds video latency without a matching audio delay. A drifting or intermittent fault is more often a clocking problem, where two devices run on slightly different references.
Note down which sources are affected. If only the studio camera feeds are wrong but the playout server is fine, that narrows the search considerably. If everything is wrong, look at the final stages of the chain first. A short written description saves a good deal of time later.
- Where is the fault visible: programme, monitor, recording or stream
- Steady offset or drifting over time
- Which sources are affected and which are fine
- Whether it appeared after a recent change
Draw the signal chain on one sheet
An audit can only be as good as the picture you give of the chain. Before deciding to commission one, try drawing your signal path from microphone and camera through to the final output on a single page. Include every box that touches the signal, even those you think are transparent: embedders, de-embedders, routers, converters, multiviewers, encoders.
The exercise is revealing in itself. Teams often find a device nobody remembered adding, or a path where audio travels separately from video for part of its journey. Mark each point where audio and video are separated and where they rejoin, because those are the places where timing usually goes wrong.
The drawing does not need to be neat. A photographed whiteboard or a hand sketch is enough for a first review. What matters is that it is honest about the real arrangement rather than the one in the original design document, which may be several revisions out of date.
- List every device the signal passes through
- Mark where audio and video separate and rejoin
- Note the format at each stage, for example HD or UHD
- Include remote contribution and return feeds
Check how your equipment is clocked
Clocking is the part of audio sync that people tend to leave until last, and it is often where the real cause lies. Find out whether your studio runs from a central reference generator, and whether every piece of equipment is actually locked to it rather than free-running on its own internal clock.
Digital audio devices that are not locked together will, sooner or later, drop or repeat samples. The result may be a faint click, a slow drift against the picture, or nothing audible at all until a long recording reveals the offset. Look at the status screens of your mixers, converters and recorders and note what each one reports as its sync source.
If you cannot answer this question quickly, that is itself useful information. It tells you the audit should include a clocking survey, and it tells whoever carries it out where to look first. Write down any device where the reference setting is unclear or set to automatic.
- Is there a single master reference for the studio
- What sync source does each device report
- Any device set to internal or automatic clocking
- Any link between different sample rates
Gather measurements you already have
You may hold more evidence than you realise. Check whether anyone has recorded a clapperboard, a countdown with a visible flash and audible beep, or a lip-sync test pattern through the chain. Even a phone recording of a monitor next to a loudspeaker can give a rough indication of the size of the offset.
Collect any equipment documentation that states processing delay. Manufacturers usually publish video latency figures in lines or milliseconds, and knowing these lets a reviewer check your sums rather than start from nothing. Keep note of firmware versions too, since a software update can change the delay a device introduces.
Do not worry if the figures are incomplete. A good audit expects gaps and fills them by measurement. What you are aiming for is a starting file: a description of the fault, a drawing, a list of settings and whatever test material exists. With that in hand, the review is spent on analysis rather than on collecting basics.
- Any recorded clap, flash and beep or test pattern
- Manufacturer delay figures for each device
- Firmware versions and dates of recent updates
- Past complaints from viewers or production staff
Decide what you want the audit to deliver
Be clear about the outcome before you ask. Some teams want a diagnosis of one stubborn fault. Others want an assessment of the whole chain ahead of a studio refit or a move to a new format. These are different jobs, and the second takes longer and covers more ground.
Decide also who will act on the findings. A report that recommends adding fixed audio delay is easy to apply. One that recommends changing the clocking arrangement may need an engineer on site and a window off air. Knowing your constraints, such as limited rehearsal time or equipment you cannot take out of service, lets the recommendations be realistic.
Finally, think about how you want the findings presented. A written report with prioritised fixes suits most gallery and engineering teams, with the quick corrections listed apart from the larger changes. If a manager needs to approve the work, ask for a short summary that can be read without the technical detail.
- One fault diagnosed or the whole chain reviewed
- Who will carry out the recommended changes
- Windows available for testing off air
- Format of the report your team needs
Questions to settle before you get in touch
When you enquire about an audit, a few practical points help the quotation to be accurate. State the type of production, whether live, recorded or both, and roughly how many sources and outputs the chain has. Mention if outside broadcast or remote contribution is involved, since network links add their own delay and variation.
Say whether the work can be done from documents and recorded material alone, or whether you expect measurements on your own equipment. Remote assessment suits clearly described faults, while a complex studio may justify more detailed investigation. Either way, a written quotation sets out what is covered before any invoice is raised.
Allow some time between the first conversation and the report. Good sync analysis needs careful reading of the evidence, and rushing it tends to produce a vague answer. If your fault is affecting live output now, say so, and explain what a temporary workaround might need to look like.
- Type of production and number of sources and outputs
- Any outside broadcast or remote feeds involved
- Remote review or measurement on your equipment
- How urgent the fault is for live output
A sync audit works best when you arrive with a clear description of the fault, an honest drawing of the chain, a note of how everything is clocked and a view of what you want back. None of this needs specialist tools, only an afternoon of careful looking. If you work through the list and still cannot explain the problem, that is a sound reason to ask for help, and the paperwork you have gathered will make the first conversation far more productive.