Author Topic: Extreme slow video player  (Read 1929 times)

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Offline PinheadBETopic starter

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Extreme slow video player
« on: December 23, 2023, 03:59:02 pm »
Hi,

I have a bunch of old Android Tablets laying around that I would put to good use.
Some of them have already become a weather connected weather station, and it works very well.

I would like to use one as an extremely slow video player.    Tha kind that plays a second of movie over the course of one minute, for example.

The idea came from various projects I saw online, but almost all of these involve an hardware reader (Raspberry, for one) and a screen.

I would like to do that only with an Android app reading a common mp4, avi, mkv or whatever video file, at a very slow speed (down to 1/100)

All the apps I've seen so far go not slower than 0.25 x the speed.

Does anyone know an app that could do the trick, and functionning on older versions of Android ?   Or an extension for VLC (strangely, even VLC for Android does not go under 0.25 x either....)

Any suggestion welcome.

Thanks
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Online macboy

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Re: Extreme slow video player
« Reply #1 on: December 24, 2023, 03:14:56 pm »
If you don't mind having to create a special slow motion version of each video, you can use a tool like ffmpeg to space the frames out to 1 frame per second (or whatever you like) then re encode. Then you can play back on any video player since it is technically playing full speed.

If you wanted to get really clever you could set up an avisynth filter (Windoze) which could frame interpolate to 100x the original frame rate, before slowing down. Then you would be able to see objects in the video smoothly moving very very slowly, rather than jumping forward once per second or two.
 
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Offline PinheadBETopic starter

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Re: Extreme slow video player
« Reply #2 on: December 24, 2023, 11:46:37 pm »
Thanks for your answer.

How could I go even slower than 1 fps ?   
Ideally, I'd like to have 1 frame per minute

EDIT: I used the following command line to slow down by 100x, but the file get enormous..... (from 16 MB to 616 MB for a simple short test file)
ffmpeg -i  d:\input.mp4 -filter:v "setpts=100.0*PTS" d:\output.mp4

Is there anyway to avoid this inflation ?

I would also like to suppress all audio streams from the output file.  How can this be done .
« Last Edit: December 25, 2023, 12:04:26 am by PinheadBE »
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Online wraper

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Re: Extreme slow video player
« Reply #3 on: December 24, 2023, 11:59:50 pm »
Ideally, I'd like to have 1 frame per minute
It's called a slide show at this point, not video.
 

Offline PinheadBETopic starter

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Re: Extreme slow video player
« Reply #4 on: December 25, 2023, 12:05:22 am »
It's called a slide show at this point, not video.

Yes, that's the whole point: having a movie running on several days as if it was a photoframe displaying a slide show
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Offline Halcyon

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Re: Extreme slow video player
« Reply #5 on: December 25, 2023, 01:21:42 am »
Could you use the scripting function within VLC to essentially just progress the video one frame at a time while the video itself is paused?
 

Offline PinheadBETopic starter

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Re: Extreme slow video player
« Reply #6 on: December 25, 2023, 03:57:35 pm »
I found how to re-encode it with a different fps rate, including values less than 1
(Here is the doc: https://trac.ffmpeg.org/wiki/How%20to%20speed%20up%20/%20slow%20down%20a%20video )


Code: [Select]
ffmpeg.exe -i input.mp4 -map 0:v -c:v copy -bsf:v h264_mp4toannexb raw.h264
ffmpeg.exe -fflags +genpts -r 0.1 -i raw.h264 -c:v copy output.mp4

The first command line extracts the video stream as raw data in the temporary file raw.h264, and the second line re-encodes that raw data with the new framerate in the output file

In the second line, the fps value is after the -r option (here, 0.1 means 1 frame every ten seconds)
Input and output files may be of any format supported by ffmpeg and installed libraries

Easy to put in a .bat file, replacing the file names and framerate with parameters.
raw.h264 can have any name and may be deleted after use.

I didn't try (yet) to smooth the result by interpolating frames (See in the page linked above) because I fear this will inflate the filesize too much

Hope this could be of use to someone.....

Let me know what you think, or if you see ways of improvement

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