when i built ffmpeg to push raspberry pi 4 camera stream to my sever,I get Unknown input format: 'h264' ERROR

Question

input:

raspivid -o - -t 0 -vf -hf -fps 10 -b 500000 | ffmpeg -re -ar 44100 -ac 2 -acodec pcm_s16le -f s16le -ac 2 -i /dev/zero -f h264 -i - -vcodec copy -aco