Large pixel-count or frame-count AVIs can be converted frame-by-frame to PNG. One can then use Irfanview or other common image browser to flick back and forth between movie frames.

The conversion occurs using ImageMagick (which itself calls FFmpeg in this case).

convert -verbose CMOSvideoshorter_halfspeed.avi -type Grayscale CMOSvideo_%03d.png