Command
ffprobe rtsp://localhost/myvideo -codec:v libx264 -show_frames -of csv
Output
Failed to set value 'libx264' for option 'codec:v': Option not found
But libx264 seems to be installed -
sudo apt install libx264-dev:
Reading package lists... Done
Building dependency tree
Reading state information... Done
libx264-dev is already the newest version (2:0.152.2854+gite9a5903-2).
libx264 is an encoder. ffprobe only probes and prints information about existing media inputs - there's no scope for an encoder to be specified. Remove -codec:v libx264.