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I am concatenating two mp4 videos. The problem is that first video (intro.mp4) lasts 5 seconds, second video (output.mp4) lasts 2 seconds and video created by concatenating them lasts 9 seconds (and should last 5+2 = 7 seconds). In final.mp4 video the last frame from first video (intro.mp4) i shown for additional 2 seconds before second video (output.mp4) is played. It looks like a lag when watching video. What I am doing wrong?

list.txt:

file 'data/intro.mp4' file 'output.mp4'

command:

./bin/ffmpeg -f concat -i list.txt -c copy final.mp4

output:

ffmpeg version 2.7.2 Copyright (c) 2000-2015 the FFmpeg developers built with llvm-gcc 4.2.1 (LLVM build 2336.11.00) configuration: --prefix=/Volumes/Ramdisk/sw --enable-gpl --enable-pthreads --enable-version3 --enable-libspeex --enable-libvpx --disable-decoder=libvpx --enable-libmp3lame --enable-libtheora --enable-libvorbis --enable-libx264 --enable-avfilter --enable-libopencore_amrwb --enable-libopencore_amrnb --enable-filters --enable-libgsm --enable-libvidstab --enable-libx265 --disable-doc --arch=x86_64 --enable-runtime-cpudetect libavutil 54. 27.100 / 54. 27.100 libavcodec 56. 41.100 / 56. 41.100 libavformat 56. 36.100 / 56. 36.100 libavdevice 56. 4.100 / 56. 4.100 libavfilter 5. 16.101 / 5. 16.101 libswscale 3. 1.101 / 3. 1.101 libswresample 1. 2.100 / 1. 2.100 libpostproc 53. 3.100 / 53. 3.100 [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f8a6a80e600] Auto-inserting h264_mp4toannexb bitstream filter Input #0, concat, from 'list.txt': Duration: N/A, start: 0.000000, bitrate: 1296 kb/s Stream #0:0: Video: h264 (High) (avc1 / 0x31637661), yuv420p, 960x540, 1163 kb/s, 23.98 fps, 23.98 tbr, 11988 tbn, 47.95 tbc Stream #0:1: Audio: aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 133 kb/s [mp4 @ 0x7f8a6c006a00] Codec for stream 0 does not use global headers but container format requires global headers [mp4 @ 0x7f8a6c006a00] Codec for stream 1 does not use global headers but container format requires global headers Output #0, mp4, to 'final.mp4': Metadata: encoder : Lavf56.36.100 Stream #0:0: Video: h264 ([33][0][0][0] / 0x0021), yuv420p, 960x540, q=2-31, 1163 kb/s, 23.98 fps, 23.98 tbr, 11988 tbn, 11988 tbc Stream #0:1: Audio: aac ([64][0][0][0] / 0x0040), 48000 Hz, stereo, 133 kb/s Stream mapping: Stream #0:0 -> #0:0 (copy) Stream #0:1 -> #0:1 (copy) Press [q] to stop, [?] for help [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f8a6a80e600] Auto-inserting h264_mp4toannexb bitstream filter frame= 258 fps=0.0 q=-1.0 Lsize= 997kB time=00:00:09.84 bitrate= 829.5kbits/s video:897kB audio:93kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.634306%
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  • Are the videos definitely encoded the same way - same video and audio codecs within the mp4 files? ffmpeg mp4 concat the way you are using it only works properly if this is the case, I think. Commented Sep 24, 2015 at 9:46
  • I'm seeing this problem as well. Files are two successive mpg's from the same camera, seconds apart. I'm quite sure they're both the same codecs and format. Commented May 10, 2016 at 16:52

2 Answers 2

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I was having the same problem with 2 mpg files. I was using this command:

ffmpeg -i "concat:foo.mpg|bar.mpg|" -c copy out.mpg

I found this link:

https://ffmpeg.org/pipermail/ffmpeg-user/2013-March/013933.html

which suggested setting the duration explicitly with the duration directive in an input file, i.e. a file looking like this:

file foo.mpg duration 6 file bar.mpg duration 4.5

where the numbers are in seconds.

Oddly, when I switched to using an input list from a file, the problem went away even without setting the duration. Very odd. I double checked and consistently got the pause with the command line list and none with the file list in a text file.. Obviously that's not working for you, as you've already got an input list file, but the duration trick might be worth a try.

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For me this happened when my video files lenght was not just in seconds but in milliseconds as well. The little pause is to stretch the last frame till it fill out that second.

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