How to move an (overlayed) image across a video in ffmpeg?

Question

moving crop works for video, but I could not make it work for a (jpg) image. How to move an image in the video using ffmpeg?

Here is my try that does not work ($TST is a .jpg):

ffmpeg -ss 30 -i main.mkv -i $TST -filter_complex \
    "color=c=${CG}:size=1380x1080,[0]overlay,\
    chromakey=${CG}:.031:0.025,despill[a];[1]crop=w=1920:h=1080:x='t*in_w/3':y='t*in_h/3'[b];[b][a]overlay" \
    -c:v ffv1 -map 0:a -c:a copy -t 1s tstres.mkv

Answer 1

An image is treated by ffmpeg as video stream with one frame. For a crop animation to be effected, you need a stream of frames.

Add loop before the image input: -loop 1 -i $TST. Normally, you would be advised to limit the duration by also adding -t, but since you limit duration on the output, it is not necessary here.