I see, I didn’t know ffplay could do some ffmpeg stuff by itself but it makes sense (ffplay is bundled with ffmpeg). I tried a very small example, you have to tweak it:
-vf drawtext=“fontsize=20:fontcolor=white:text=example line of text:y=h-line_h:x=mod(w+text_w-50*t,w)”
It makes the text scroll right to left, looping back to the start when it goes off screen. I adapted it slightly from the examples section of the manual: ffmpeg.org/ffmpeg-filters.html#Examples-71