I have 15 video files which I want to merge with ffmpeg. I want to save time by merge all of the video files in a single command line, not cut it one by one and merge it. Thanks.
Use the concat demuxer.
First, create a text file with the filenames.
file '1.mp4' file '2.mp4' file '3.mp4' ... file '13.mp4' file '14.mp4' file '15.mp4'
Then, run the concat command.
ffmpeg -f concat -i textfile -c copy -fflags +genpts merged.mp4
For this to work, all videos should have same properties such as codec, resolution, framerate, sample rate, etc.
If they are not, you can encode the concat.
ffmpeg -f concat -i textfile -fflags +genpts merged.mp4
Also see FFmpeg Wiki: Concatenate.
Gyan's suggestion did not work for me. The output video from the suggested commands had the same duration as the first input, and so video 2 and 3 content was missing, and my media player crashed trying to play the output.
I did however find my answer in the reference he provided: http://trac.ffmpeg.org/wiki/Concatenate#filter
ffmpeg -i v1.mp4 -i v2.mp4 -i v3.mp4 -filter_complex "[0:v:0][0:a:0][1:v:0][1:a:0][2:v:0][2:a:0]concat=n=3:v=1:a=1[outv][outa]" -map "[outv]" -map "[outa]" v_out.mp4
This command worked for videos all having both video and audio streams. For one video not having audio, I modify the command slightly like so:
ffmpeg -i v1_NoAudio.mp4 -i v2.mp4 -i v3.mp4 -filter_complex "[0:v:0][1:v:0][2:v:0]concat=n=3:v=1[outv]" -map "[outv]" v_out_NoAudio.mp4
Effectively, I just removed any portions of the command about audio. This discards the audio from the second and third videos, as a rule of using this filter is that the channels remain the same in all videos.