VirtualBoyFilters

Filters to beautify videos or screenshots of monochrome Virtual Boy games

Virtual Boy videos look better with colors! In the following I describe how to convert a video of a Virtual Boy game using the command line tools FFmpeg and ImageMagick.

Requirements

• FFmpeg for converting the video into pictures of single frames and converting the modified frames back to a video.
• ImageMagick for applying a filter to every video frame. A file colors.png (sample in this repository), which contains the colors that will be used for translating grayscale values to colors.

Steps

• Install FFmpeg and ImageMagick and add both to PATH.
• Download colors.png to the same folder as the video (referred to as video.mp4 in commands) and open a command line in that folder.

Depending on your command line interpreter, you will have to escape parentheses with a backslash. If necessary shorten the video's duration (here the cut begins after 1 minute 30 seconds and runs for 10 seconds.

ffmpeg -ss 0:1:30 -i video.mp4 -t 0:0:10 short.mp4

Extract the video's sound.

ffmpeg -i short.mp4 -f mp3 sound.mp3

Extract the video's frames.

mkdir frames/
ffmpeg -i short.mp4 frames/%04d.png
mkdir out/

Apply filter to frames. (Alternative 1 for short videos or PCs with much free RAM. Modify 1280x720 to match the image dimensions).

convert frames/*.png null: ( -clone 0--1 -blur 12x12 -append colors.png -clut -crop 1280x720 +repage ) -compose multiply -layers composite +adjoin out/%04d.png

Apply filter to frames. (Alternative 2 if Alternative 1 is too slow; for Windows Command Line).

for %f in (frames/*.png) do convert %f ( +clone -blur 12x12 colors.png -clut ) -compose multiply -composite out/%f

Convert the modified frames back to a video with sound.

ffmpeg -i out/%04d.png -i sound.mp3 -o out.mp4

Caveats

Applying the filter can be slow. Ways to speed it up:

• Leave out the "-blur 12x12" part or use smaller blur parameters.
• Only have a few frame images in the frames/ folder at a time. I tried it with 300 frames without issues.

Conversion needs much disk space, because pictures of every video frame need to be written to the hard drive first.

References

colors.png created using a technique by Fred Weinhaus