How to put a new voice track on a video and keep it in step
Upload the video and the new audio. Vizard Agent transcribes both tracks to compare what they say and when, maps every text card and shot change in the picture, then re-times the video so each card still arrives on the words that belong with it.
What do you type into Vizard Agent?
Say explicitly what has to stay aligned once the audio changes. Vizard Agent will otherwise simply attach the new track and hand it back, which is technically exactly what you asked for and leaves every text card arriving at the wrong moment. Say whether the new script is a rewrite, because that changes how much re-timing is needed.
Prompt
What does Vizard Agent actually do?
Swapping one audio file for another takes seconds. Keeping the picture in step is the actual job, because every card and cut was timed against a narration that no longer exists, so most of the work happens before the swap itself, here on a slide-based video. In the session behind this article it:
- Checked the duration and format of both the video and the new audio, and transcribed both tracks to compare their content and their timing.
- Extracted a frame per second to analyse the video's slide structure, mapped the shot and slide changes, and built thumbnails of every shot.
- Analysed the text and the duration of every text card, alongside the word-by-word transcript.
- Checked the new audio's exact duration and its ending, and measured its loudness.
- Combined the video with the new audio, trimmed it to that length, and built a montage of the closing frames to review the ending.
- Uploaded the result and analysed the finished video end to end.
When does this not work well?
Re-timing a picture around a new voice track has real limits, and almost all of them come from how far the new script has drifted from the old one. A complete rewrite may leave nothing to align to, much longer audio outruns the picture, much shorter audio cuts cards before they can be read, and burnt-in captions still show the old words.
Common questions
Can it just attach the audio? Yes, if that is all you want. Vizard Agent will say when the cards will end up misaligned.
What if my new script is different? It compares both transcripts. Vizard Agent tells you how far apart they are.
What if the new audio is longer? Something has to give. Vizard Agent can hold shots longer or extend the last one.