How to trim video by multiple frame numbers then concatenate using FFMPEG

问题

Using following code, I'm able to trim video by time:

ffmpeg -i input.mp4 -filter_complex \
"[0:v]trim=60:65,setpts=PTS-STARTPTS[v0]; \
 [0:a]atrim=60:65,asetpts=PTS-STARTPTS[a0]; \
 [0:v]trim=120:125,setpts=PTS-STARTPTS[v1];
 [0:a]atrim=120:125,asetpts=PTS-STARTPTS[a1]; \
 [v0][a0][v1][a1]concat=n=2:v=1:a=1[out]" \
-map "[out]" output.mp4

Above code trim video from 60-65 sec & 120-125sec then concatenate in output.mp4 file.

Need to know how to trim video by using frame number and concatenate.

---

Is it possible to get the time by using Frame Number and fps?

frame_1_start = 100 #Frame Number
frame_1_end   = 200 #Frame Number
frame_2_start = 450 #Frame Number
frame_3_end   = 700 #Frame Number
fps = 20 # Frame per second

time_x_1 = frame_1_start/fps
time_x_2 = frame_1_end/fps
time_y_1 = frame_2_start/fps
time_y_2 = frame_2_end/fps

ffmpeg -i input.mp4 -filter_complex \
"[0:v]trim=#{time_x_1}:#{time_x_2},setpts=PTS-STARTPTS[v0]; \
 [0:a]atrim=#{time_x_1}:#{time_x_2},asetpts=PTS-STARTPTS[a0]; \
 [0:v]trim=#{time_y_1}:#{time_y_2},setpts=PTS-STARTPTS[v1];
 [0:a]atrim=#{time_y_1}:#{time_y_2},asetpts=PTS-STARTPTS[a1]; \
 [v0][a0][v1][a1]concat=n=2:v=1:a=1[out]" \
-map "[out]" output.mp4

回答1:

As shown in the trim filter documentation use the start_frame and end_frame options.

Video only

ffmpeg -i input.mp4 -filter_complex \
"[0:v]trim=start_frame=25:end_frame=100,setpts=PTS-STARTPTS[v0]; \
 [0:v]trim=start_frame=200:end_frame=300,setpts=PTS-STARTPTS[v1];
 [v0][v1]concat=n=2:v=1:a=0[v]" \
-map "[v]" output.mp4

Video & audio

ffmpeg -i input.mp4 -filter_complex \
"[0:v]trim=start_frame=25:end_frame=100,setpts=PTS-STARTPTS[v0]; \
 [0:a]atrim=1:4,asetpts=PTS-STARTPTS[a0]; \
 [0:v]trim=start_frame=200:end_frame=300,setpts=PTS-STARTPTS[v1];
 [0:a]atrim=8:12,asetpts=PTS-STARTPTS[a1]; \
 [v0][a0][v1][a1]concat=n=2:v=1:a=1[v][a]" \
-map "[v]" -map "[a]" output.mp4

For atrim you can use timestamps as in your original command, or use start_sample and end_sample if you prefer to use audio samples instead. atrim does not have start_frame and end_frame.

For example, if frame rate is 25, and you want trim to include frames 25-100, then atrim would use atrim=1:4.

You can use ffprobe to get frame rate and to check if an input has audio.

来源：https://stackoverflow.com/questions/63656881/how-to-trim-video-by-multiple-frame-numbers-then-concatenate-using-ffmpeg