User PHP đang chạy:
thuyenvi

PATH:
/usr/local/bin:/bin:/usr/bin

which ffmpeg:
which: no ffmpeg in (/usr/local/bin:/bin:/usr/bin)

whereis ffmpeg:
ffmpeg:

Thử /usr/bin/ffmpeg:
sh: /usr/bin/ffmpeg: No such file or directory

Thử /usr/local/bin/ffmpeg:
sh: /usr/local/bin/ffmpeg: No such file or directory