Use of FFmpeg movie and amovie

movie

• movie can be used to load a video input, same as -i command

amovie

• amovie is used to load an audio input

the difference

• movie is a filter that can be written in filter_complex. The advantage of this is that it can be used at any time and input at any time, and there is no need to remember the id of the input source. The disadvantage is that many Main options parameters cannot be used, such as itsoffset delayed playback
• -i is Main options, the input and processing are separated, and the input source is obtained through [id:v]. The disadvantage is that when there are too many input sources, the id of each input source needs to be marked

usage

• movie

movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [over];
[in] setpts=PTS-STARTPTS [main];
[main][over] overlay=16:16 [out]

• -i

ffmpeg -i input1.mp4 -i input2.mp4 [0:v][1:v]overlay -y out.mp4