Synchronise a clear event near the start and compare another near the end before editing a long recording. I would distinguish a constant start offset from clock or rate drift. Matching the nominal sample-rate labels does not prove that two independent recorders ran for exactly the same duration.
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I would measure a long take before detailed editing and fix a demonstrated rate relationship once. Keep a short sync record so later collaborators understand any intentional retiming.
Measure a stable relationship
Use a clap, slate or other identifiable event present in both recordings. Check the beginning, middle and end of a continuous section. If the discrepancy changes abruptly, investigate a pause, dropped section or edit rather than assuming a smooth clock difference.
Record the video frame-rate interpretation and audio sample-rate interpretation. A wrong interpretation can change duration, while independent device clocks can also differ slightly. Keep those possibilities separate and preserve the originals before any retiming.
Correct the source relationship
For a constant offset, move the audio appropriately and verify several points. For a consistent gradual difference, use the editor’s supported duration or time-stretch workflow on a copy, with pitch and quality review as required. Do not correct a long continuous take by repeatedly chopping it into unexplained tiny shifts.
Listen after the correction and inspect lip sync or visible impacts. Check both beginning and end again in the rendered output. A waveform alignment at one point is not a complete sync test, especially after an export or frame-rate conversion.
An illustrative duration comparison
Two recordings align at the opening event, but one reaches a final event two seconds later after an hour. The relative difference is about 2 ÷ 3600, or 0.0556%. That suggests a small rate relationship to investigate; it does not prove which device or interpretation caused it. Preserve the source and test a controlled correction.
Before you act
- Compare at least three positions.
- Distinguish smooth drift from missing sections.
- Recheck lip sync in the rendered output.
Use the Frame-rate duration converter to apply the guide to your own setup.
Keep exploring
- Variable frame rate and audio sync
- Conform or convert frame rate? Decide whether duration should change
Method note: this is an original planning procedure with illustrative inputs. It does not report a physical product test. Check the exact product, edition and official instructions before acting.
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