One thing RPiLooper is picky about is the format of the video it is fed. Here’s a method of converting your video into a usable format.

1. Download and install Avidemux: http://fixounet.free.fr/avidemux/download.html
2. Open your video file with Avidemux.
3. Set Video Output to Mpeg4 AVC (x264)
4. Configure Video Output - under the General tab, change the Encoding Mode to Constant Quantiser (Single Pass), and shift the Quantizer slider down to a value of 5. (You can play around with values here, as the lower the value is the larger the file will be - 5 works for me). Don’t change anything else.
5. Set Output Format to Video Only. No configuration changes are necessary here.
6. Save your file.
7. Profit.