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.

• 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.

• 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

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.

colors.png created using a technique by Fred Weinhaus