How to speed up the footage under a voiceover without speeding up the voice
Give Vizard Agent the timecodes to speed up and say the voiceover must stay natural. It speeds up only the picture, finds a pause in the narration near that section that is long enough to absorb the time saved, removes exactly that much silence, and checks the total frame count so everything after the change stays in sync.
What do you type into Vizard Agent?
Give the stretch as timecodes and say what must not change. "Speed up 1:57 to 2:00" is enough for the picture, but the voice decision is yours to state: a sped-up narrator sounds rushed, and without that instruction the obvious edit speeds up everything in the range.
Speed up from 1:57 to 2:00 but keep everything else the same.
What does Vizard Agent actually do?
It treats the change as time accounting. A three-second section played at double speed lasts a second and a half, and that missing second and a half has to come from somewhere in the soundtrack, or every line after it lands early. In the session behind this article it:
- Pulled frames across the section to see what would play faster, and ran silence detection on the narration track.
- Found a two-second gap with no speech right where the change sits.
- Rendered the section at double speed into an exact number of frames.
- Removed exactly the time saved from that gap, in both the narration and the full mix, with a short crossfade on the music.
- Checked the rebuilt video still totalled the same number of frames as planned, and had the window around the change reviewed for clipped words or overlaps.
Later, when the sped-up section moved to a new spot, it re-cut only the picture and confirmed by hashing that the audio had not changed at all.
When does this not work well?
When the narration has no pause near the section. If the voice talks straight through, the only places to take time from are the gaps further away, and then the words drift away from the pictures they describe for a stretch. Speeding the voice slightly is sometimes the lesser evil there.
Common questions
Why does my voiceover get ahead after a speed-up? The picture got shorter. Vizard Agent takes the time from a pause.
Will the narrator sound faster? No. Vizard Agent leaves the voice at its natural pace.
What if I move the fast section later? Vizard Agent re-cuts the picture and leaves the audio untouched.