Stack images with "hstack"-filter from video or image sequence in ffmpeg
You're better off using the tile filter for this:

ffmpeg -i INPUT.mov -vf fps=1,scale=192:108,tile=54x1 output.jpg


The tile argument is the size of a rectangle. So for a 54 second video, 54x1 produces a horizontal stack of 54 frames. Use 1x54 for a vertical stack.