Set framerate (change video speed)

Kagami / boram

:film_strip: Cross-platform graphical WebM converter

https://github.com/Kagami/boram/releases

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Set framerate (change video speed) #40

Open sturmen opened 5 years ago

sturmen commented 5 years ago

Hi! I have a habit of watching a lot of YouTube videos on 2x speed, and I've built myself a pipeline using youtube-dl & ffmpeg to download offline copies of videos, and re-encode them to save file size AND turn 24fps content into 48 fps content by playing it back twice as fast. Here's the filter chain I use:

-filter_complex "[0:v]subtitles='subtitles.vtt':force_style='FontName=Roboto',setpts=0.5*PTS[v];[0:a]atempo=2.0[a]" -map "[v]" -map "[a]"

Would it be possible to add a slider (or even a checkbox) to add the setpts & atempo filters to my filter change in boram? Thank you!

Kagami commented 4 years ago

Seems like a lot of users request this feature.

As a workaround, if FPS of your video is 24:

To speedup 2 times: -vf "setpts=PTS/2" -r 48
To slowdown 2 times: -vf "minterpolate=48,setpts=PTS*2"
To slowdown 2 times without interpolation: -vf "setpts=PTS*2" -r 12

If you're cutting some fragment you need to specify the duration with -t option as well (two times lower for speedup or bigger for slowdown respectfully).