Video audio syncing can be relatively straightforward, but it quickly becomes problematic when the correct workflow is not followed from the start. As a BBC-trained video editor with over 15 years of experience, I have developed the skills to resolve even the most challenging syncing problems. In this article, I share a difficult real-world video-audio syncing case study and follow it with practical best-practice guidance.
How video audio syncing works
In most cases, some form of sync sound records alongside the video during filming. If a production uses an external audio recorder to improve flexibility or recording quality, an editor must then sync that external audio to the camera’s guide sound. Getting this right depends heavily on the quality of the original recordings and the file management decisions made on set.
A problematic video audio syncing case study
A recent short film project presented a serious video audio syncing challenge. The camera’s built-in microphone had recorded almost no audible sound. The only useful audio from the camera was the clapperboard strike. The separately recorded audio, captured on a Zoom recorder, had not had headphone monitoring during recording. As a result, the quality was very poor throughout.
Furthermore, the audio files sat inside a series of nested folders with no consistent naming conventions and no useful metadata. Consequently, automated syncing software could not handle most of the recordings. Almost everything needed manual intervention to sync correctly.
How I resolved the video audio syncing problems
To tackle these issues, I first moved all audio files into a single main folder. Once I had done that, I organised the sound files into groups based on their creation dates. This revealed that four distinct creation dates in the audio matched four distinct creation dates in the camera footage.
I then edited each separate day’s recordings together and ran four separate PluralEyes syncs, one for each filming day. This allowed me to identify clearly which portions of audio still needed manual syncing. For those remaining sections, I watched the footage and synced the sound by ear, comparing the audio waveforms to the visuals frame by frame.
Managing poor quality audio recordings
Because of the poor recording quality and weak file management, working out how to sync the sound to the picture took a considerable amount of time. Additionally, once the syncing completed, I discovered that some of the supplied audio had no connection to the film at all. This complicated the process further.
Although this was a short film with only five hours of footage, it took a disproportionately long time to edit as a result. The edit also needed significant adaptation to work around the sound rather than the performances. A detailed sound mix was then necessary to reduce background noise and smooth together the different recording qualities throughout.
What I learned
This project reinforced for me the critical importance of good working practices when recording and delivering sound for video editing and audio mixing. It also made clear that I need to carry out a thorough technical assessment of any future project I have not filmed or recorded myself. Doing so allows me to estimate the editing time more accurately before committing to a delivery schedule.
Video audio syncing: good working practices on set
To avoid the problems described above, follow these best practices when recording audio on camera or a separate device:
- Use a clapperboard, or a loud in-vision clap, at the start of every take. This creates an audio peak alongside a clear visual reference for syncing.
- Start the audio recording before the camera rolls and let it continue after the take ends. Consider keeping the recorder running between takes.
- Always monitor audio with well-sealed headphones throughout recording.
- Use a professional sound recordist wherever possible to ensure a reliable recording.
- Record usable sync sound on the camera at a good level, even when using an external recorder. Consider feeding a mixer output directly to the camera input.
- Set matching timecodes on all recording devices. Free run time-of-day timecode on both camera and audio recorder helps the editor enormously, even if the devices cannot lock timecode precisely.
Different methods for video audio syncing
If you encounter video audio syncing problems in post-production, the following methods may help:
Assess your audio first. Make a copy of all master recordings and explore what information they contain. Understanding the differences between recording types helps you choose the right syncing approach from the outset.
Check the metadata. Bringing all file data together lets you compare metadata headings across files. These differences can reveal useful information about how and when each file was recorded.
Sync one day at a time. For complex projects, working through each filming day separately makes automated software more effective and manual syncing more manageable.
Sync manually by ear. Problem audio can always be synced by listening carefully and comparing the sound to the picture. This is time-consuming but reliable.
Use clapperboard sync points. A clapperboard provides both a visual and an audio cue point simultaneously. Any sharp, hard sound works if no clapperboard is available. Make sure the board or clap appears clearly in frame.
Match waveform peaks to visual actions. Identifying peaks in the audio waveform and matching them to visible on-screen actions is an effective manual syncing technique.
Calculate timecode offsets. If the audio recorder timecodes do not match the camera timecodes, calculate the offset for each clip and apply it consistently throughout the sync process.
Use automated syncing software. Search for some software that is compatible with your computer hardware and software. Your editing software might help with your sync problems. Autosync is available on Avid Media Composer.
Summary: resolving video audio syncing problems
To summarise the key points from this article:
- Good on-set practices prevent most video audio syncing problems before they reach post-production.
- Always monitor audio recordings with headphones and use a clapperboard on every take.
- Organise audio files clearly with consistent naming conventions and good metadata.
- For complex syncing projects, sync one filming day at a time.
- Use automated software as a first pass, then check and fix remaining issues manually.
- Assess any unfamiliar project technically before committing to a delivery estimate.
I consider myself highly skilled in resolving challenging video and audio syncing problems and would be happy to help or advise should you need any assistance. If you would like any help with your video editing and post-production, please get in touch. Check out my video production online portfolio to view more examples of my work.
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