I'm using Eprime and Experiment Builder which requires files in AVI format (AVI-XVid). The files are quite small already (various 2 second clips under 1mb), but are still too large which crash the system, thus I am looking into reducing the file size by changing the bitrate, resolution, frame rate etc. I am not familiar with video editing, any help would be appreciated!
Premier Pro doesn't encode XViD, you'll need to rely on another solution such as FFmpeg. Using FFmpeg is a different question but the command will be something similar to:
ffmpeg.exe -y -i "in.xvid" -t 480.00 -vf scale=720:301,pad=720:576:0:137 -map 0:v:0 -map 0:1 -b:v 2500K -vcodec libxvid -aspect 1.25 -b:a:0 128K -ac:a:0 2 -ar:a:0 48000 -codec:a:0 libmp3lame "out.avi"
you'll need to tinker with these settings to get the exact quality you want