Hi, I've got around 100 movies. Part of them are AVI: [avi @ 0x561e6733c640] non-interleaved AVI Input #0, avi, from 'V-0018.AVI':   Duration: 00:00:11.04, start: 0.000000, bitrate: 4571 kb/s     Stream #0:0: Video: mjpeg (MJPG / 0x47504A4D), yuvj422p(pc, bt470bg/unknown/unknown), 640x480, 4515 kb/s, 28.18 fps, 28.18 tbr, 28.18 tbn, 28.18 tbc     Stream #0:1: Audio: pcm_u8 ([1][0][0][0] / 0x0001), 8000 Hz, 1 channels, u8, 64 kb/s rest are MP4: Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'MAH00607.MP4':   Metadata:     major_brand     : MSNV     minor_version   : 22675568     compatible_brands: MSNVmp42isom     creation_time   : 2017-06-14T20:20:24.000000Z   Duration: 00:00:12.48, start: 0.000000, bitrate: 2795 kb/s     Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv, bt709/bt709/iec61966-2-4), 1280x720 [SAR 1:1 DAR 16:9], 2664 kb/s, 25 fps, 25 tbr, 25k tbn, 50 tbc (default)     Metadata:       creation_time   : 2017-06-14T20:20:24.000000Z       handler_name    : Video Media Handler       encoder         : AVC Coding     Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 127 kb/s (default)     Metadata:       creation_time   : 2017-06-14T20:20:24.000000Z       handler_name    : Sound Media Handler I'm using this script to convert movies (insert timestamp) -> https://gist.github.com/T4ng10r/4f57212465a32172e4a4bb7a654fcd0e As you see - timebase for both movies are different. When I concat converted movies time duration of movie is distorted, after few first AVI videos movie freeze. And in console I see lots of "Non-monotonous DTS in output stream 0:0; previous: 131753981, current: 3274138; changing to 131753982. This may result in incorrect timestamps in the output file." I've tried with adding  -r 25 to convert function for avi, with no result. The same with https://stackoverflow.com/a/41744007/603044 Mulvya - converting AVI takes ages. How should I treat AVI (which are far more less then MP4) so the final movie be correct?