ffmpeg -i first.mp4 -i second.mp4 -filter_complex
        "[0:v]trim=start=0:end=2,setpts=PTS-STARTPTS[0_clip_1];
        [0:v]trim=start=2:end=3,setpts=PTS-STARTPTS[fadeoutsrc_0];
        [fadeoutsrc_0]format=pix_fmts=yuva420p,fade=t=out:st=0:d=1:alpha=1[fadeout_0];
        [fadeout_0]fifo[fadeoutfifo_0];[1:v]trim=start=1,setpts=PTS-STARTPTS[1_clip_2];
        [1:v]trim=start=0:end=1,setpts=PTS-STARTPTS[fadeinsrc_1];
        [fadeinsrc_1]format=pix_fmts=yuva420p,fade=t=in:st=0:d=1:alpha=1[fadein_1];
        [fadein_1]fifo[fadeinfifo_1];
        [fadeoutfifo_0][fadeinfifo_1]overlay[crossfade_1];
        [0_clip_1][crossfade_1][1_clip_2]concat=n=3[output];[0:a][1:a] acrossfade=d=1 [audio]"
    -map "[output]" -map "[audio]" videoWithCrossfade.mp4


ffmpeg -i videoWithCrossfade.mp4 -filter_complex
        "/Windows/fonts/arial.ttf':text='hello world!':fontcolor=white:fontsize=40:box=1:boxcolor=red
        @0.5:boxborderw=10:x=500:y=500"
        output.mp4