Video duration, transitions and speed
The length of the video and the transitions at the start and end are set by the "Duration and transitions" page of the FRAME section. Two settings on the same topic are in other sections. Motion speed belongs to the template, the keyframe interval to file output. All five are collected below. Ranges work the same way as everywhere: see the article how uniquification works.
Five duration and speed settings
| Label | What it does | Range and units | Default |
|---|---|---|---|
| "Change video duration" | Stretches or compresses the whole video. The sound stretches together with the picture | percent, from -50% to +50% | on, from -10 to 10 |
| "Add fade in" | The picture fades in from black at the start | seconds, from 1 sec. to 30 sec. | off, from 1 to 3 |
| "Add fade out" | The picture fades to black at the end | seconds, from 1 sec. to 30 sec. | off, from 1 to 3 |
| "Change motion speed" | Speeds up or slows down the animation between template checkpoints | percent, from -50% to +50% | off |
| "Keyframe interval" | Rebuilds the structure of keyframes inside the file. Does not touch the picture at all | frames, from 1 frame to 500 frames | off, from 30 to 250 |
One more setting of this page, "Frame blending", is described in the article texture and detail.
What depends on what
Three of the five settings are not always shown.
- "Audio fade in" is a switch inside the "Add fade in" card. It is visible only when that card is on.
- "Audio fade out" is the same kind of switch inside the fade out card.
- "Change motion speed" is on the "Template" page of the OVERLAYS section and is shown together with the rest of the page when "Use template" is on. It works only when there is more than one checkpoint.
- "Keyframe interval" is on the "Performance" page of the OUTPUT section. It is visible only when "Choose codec and container" is on. With the switch off, the card is hidden together with the whole codec group, and you will not be able to find the setting.
- "Change video duration" and both transitions are always shown.
Sound does not fade by itself during transitions
By default "Add fade in" and "Add fade out" act only on the picture. The volume stays the same. Sound has separate nested switches. Please turn on "Audio fade in" and "Audio fade out" if the sound should rise and fade together with the image.
The moment the fade out starts is counted from the final duration of the copy. So the fade out works correctly together with the duration change. If the fade time is longer than the video itself, it is cut to the length of the video.
What happens to the sound when the duration changes
- The main sound track always stretches together with the picture. Only the tempo changes; the pitch of the voice stays the same.
- Additional audio stretches only when the "Change speed when video duration changes" switch is on. It is on the "Additional audio" page.
- The sound settings are covered in the article audio: volume, pitch and two equalizers.
Cost in time
None of the five settings redraws the frame. So all of them are cheap.
| How much it slows things down | Settings |
|---|---|
| Almost no slowdown | "Change video duration", "Add fade in", "Add fade out", "Change motion speed" |
| No work of its own at all | "Keyframe interval". It changes only the file structure |
Next to the keyframe interval on the "Performance" page is the frame rate change. That one slows video creation down noticeably: of the settings that change the frame, it is the most expensive. Only "File compression" set to "Maximum" and the AV1 codec are more expensive. These are two different settings with similar names.
What you see at the edges of the range
| Setting | What you see at the edge |
|---|---|
| "Change video duration" | -50%: the copy is half as long and twice as fast. +50%: one and a half times longer and slower |
| "Add fade in" | 1 sec.: a normal soft start. 30 sec.: on a short video the picture brightens almost until the end |
| "Add fade out" | 30 sec.: on a short video the darkening starts almost right away |
| "Change motion speed" | ±50%: the motion along the template is visibly jerky |
| "Keyframe interval" | The viewer will not see a difference at any value. Only the inner structure of the file changes |
Frequently asked questions
The finished copies are shorter than the original. Is this normal?
Yes, if "Change video duration" is on. By default this setting is on with the range from -10 to 10. That means some copies are up to 10% shorter than the original and some are longer. Please turn this setting off if the length of the copies must stay the same.
Why does the sound not fade at the end while the picture darkens?
The "Audio fade out" switch is off. It is inside the "Add fade out" card and is turned on separately.
I cannot find "Keyframe interval". Where is it?
It is hidden inside the "Choose codec and container" card on the "Performance" page. Please turn on this switch, and the card with the interval opens.
Which keyframe interval value did a copy draw?
It is not shown anywhere. Unlike almost all the others, this setting has no column of its own in the results table. The drawn value stays inside the file.
"Change motion speed" is on, but the speed is the same. Why?
The setting works only inside a template and only when more than one checkpoint was set when it was created. With one checkpoint there is nothing to change. The template is set up in the OVERLAYS section on the "Template" page.