I have hundreds of clips that I need to slow motion 0.5x and nothing else. All clips are 1080x1920 60fps and are exactly the same format. Here is what I do now:
have an empty ShotCut project with settings I need.
drag a clip in to “Playlist” (say Clip001.mp4)
drag the clip from “Playlist” to “Timeline”
in “Timeline”, select the clip and open up the “Properties” tab, change speed to 0.5x, press “Apply”
click “Export”, choose “From Timeline”, then click “ExportFile”
In the popped up save window, manually type in the name of the export file and hit save. I use the original clip’s name with a suffix, for example: Clip001SlowMotion.mp4
Just that I need to repeat steps 2 to 6 couple hundred times (ie Clip001.mp4 - Clip999.mp4 to export Clip001SlowMotion.mp4 - Clip999SlowMotion.mp4). Is there a more efficient way to do it?
It is not much faster but saves you a few clicks and drags. You could put all of the clips in one timeline with easy to identify gaps. Export the one movie. Import that movie slow it down export a second complete slow movie. Import the second, slow movie, split that movie on the gaps and then using the Export Sub Clip option in the Properties tab under the 3 lines(hamburger) button for each segment.
A more fundamental question… How will these hundreds of clips be used?
Slowing down video in Shotcut is done by doubling frames. Frame 1 of input gets copied to the output as Frame 1 and Frame 2, if doing a half-speed slowdown. The motion will not appear smoother than the original since the frames are not interpolated.
Hence the question… what downstream process benefits from having videos slowed down in advance? The actual frame data is the same, just played slower. Would it be easier to set the media player to half playback speed instead of converting all the clips?
If conversion is necessary, there are dedicated transcoding tools like FFmpeg and others that can do this process much more efficiently than an editor like Shotcut. We can look into that more here if you want.