How to downscale my source video files?

If your phone does not support the video resolution of your files, you might experience an error or black screen when exporting. This means you’ll need to downscale the files before you can use them with RaceChrono. Our choice for downscaling video files is a command line tool called FFmpeg:


ffmpeg -i SOURCE.MP4 -vf scale=1920:1080 -c:v libx264 -crf 14 -c:a copy DOWNSCALED.MP4

This will downscale your video to h.264 and 1080p. Edit the line for any other resolution you need. Replace the SOURCE.MP4 for which ever file you’re trying to downscale. The downscaled video will be saved to the DOWNSCALED.MP4 file.

So, if you need to downscale a file named GX010036.MP4 to h.265 and 4K, use the following command line:

ffmpeg -i GX010036.MP4 -vf scale=3840:2160 -c:v libx265 -crf 14 -c:a copy DOWNSCALED.MP4

The number after the “-crf” defines the compression level, where 0 is lossless, and the higher numbers are higher compression.