Make slow-motion

[David_UK]

Hi

I work in medical imaging and teach techniques using .avi files created by our medical software. I have recently discovered ffmpeg and can now crop and zoom the appropriate bits.

Is there a way to also slow down the video display so the students can see more detail?

I'd appreciate any suggestions. Thanks.

[Baldrick]

See http://lists.mplayerhq.hu/pipermail/ffmpeg-user/2007-April/008125.html

[David_UK]

Baldrick
Thanks for the quick reply. I've tried using the '-r' but the resulting video still has the same length when played in WMP or VLC. GSpot reports that the output file is still 15fps (same as input) even though I used '-r 5' before the input.

[Midzuki]

http://avisynth.org.ru/docs/english-traffic-exceeded/corefilters/fps.htm

http://avisynth.org.ru/docs/english-traffic-exceeded/corefilters/resampleaudio.htm

Hope this helps.

***********

[David_UK]

Er, thanks Midzuki

Most of this is over my head. Couldn't get a file to play at all....

Anyway, I'm not sure this is what I'm after. I want to re-encode the video so I can import it into Powerpoint on different PC's.

[jagabo]

If you want slow motion that's more than simply playing back the existing frames at a slower speed, or just repeating frames, you can check out the AviSynth function SmoothFPS():

https://forum.videohelp.com/topic303037.html
https://forum.videohelp.com/topic327121.html

SmoothFPS() creates in-between frames by analyzing motion within the video. It isn't perfect but can work pretty well with some material.

The original file is no longer available but you can see a half speed version produced by a simple Bob() and a 1/10 speed version from SmoothFPS():

https://forum.videohelp.com/topic303037.html#1534640

[Baldrick]

Yep, you must use avisynth or another advanced editor if you want smooth slow down. If avisynth looks too complex you can use windows movie maker to slow down it to half and export to avi or wmv.

[Alex_ander]

If you decide to use SmoothFPS() function, don't forget to load MVTools.dll plugin (the script examples from that thread don't include 'load plugin' line), that function uses one of the standard operations of MVTools.

[jagabo]

If you put MVTools.dll in AviSynth's plugins folder you don't need to explicitly load it. The downside of doing this is that starting up AviSynth is slower, and it's memory footprint is larger, as all the plugins are loaded, even if they won't be used.

[pepegot1]

Easy to do. Use Videostudio 11 and select slow motion-you can set it to your desired speed. Then save as a new file.

[David_UK]

Thanks everyone for yourhelp. AviSynth is a bit beyond me at the mo, so I'll settle for 1/2 speed in movie maker.
Thanks again.

[David_UK]

Update:
Tried RAD Video Tools (Bink) which allowed me to force the frame rate. I've not used this app much, but the quality remains fine to my eye.

[jagabo]

With AVI files you can easily change the frame rate with AviFrate. It just changes the value in the header that tells a player how long to display each frame. Of course, audio will no longer be synchronized.

[David_UK]

Hi jagabo

Thanks. Following the link, the .exe fails with an error when starting up. Searching different video websites tho' I found AVIFrate101 which is also a small, standalone app that just changes framerate - perfect - thanks!

[jagabo]

You're welcome.

[Babysittah]

Aint them players got their slowmotion features?