How to concatenate videos with ffmpeg

2020-07

So, I was testing my Fredi security cam and during the tests, I realised it does not generate continuous videos, but instead, small 3 Megabytes videos.
While I understand the tech rationale behind this, I wish it could come in a single piece so, I can make 'context aware' analysis in the future (I already did a python script to check self similarity between video frames, but this is for another post).

So, in order to concatenate the video, I used the following steps with ffmpeg (assuming you are using linux):
netto@bella:~/Desktop/video/rec126$ ls -1 | awk '{print "file " $0}' > pieces.txt

In my case, this will generate the following output:
file pieces.txt
file rec011_20200318000210_01_0325_0031.mp4
file rec011_20200318000242_01_0783_0031.mp4

Now, we are ready to concatenate (this will concatenate all files that are listed inside pieces.txt removing duplicated frames):
netto@bella:~/Desktop/video/rec126$ ffmpeg -f concat -safe 0 -i pieces.txt test.mp4
ffmpeg version 3.4.6-0ubuntu0.18.04.1 Copyright (c) 2000-2019 the FFmpeg developers
built with gcc 7 (Ubuntu 7.3.0-16ubuntu3)
configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
WARNING: library configuration mismatch
avcodec configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared --enable-version3 --disable-doc --disable-programs --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libtesseract --enable-libvo_amrwbenc
avfilter configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared --enable-version3 --disable-doc --disable-programs --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libtesseract --enable-libvo_amrwbenc
libavutil 55. 78.100 / 55. 78.100
libavcodec 57.107.100 / 57.107.100
libavformat 57. 83.100 / 57. 83.100
libavdevice 57. 10.100 / 57. 10.100
libavfilter 6.107.100 / 6.107.100
libavresample 3. 7. 0 / 3. 7. 0
libswscale 4. 8.100 / 4. 8.100
libswresample 2. 9.100 / 2. 9.100
libpostproc 54. 7.100 / 54. 7.100
Input #0, concat, from 'pieces.txt':
Duration: N/A, start: 0.000000, bitrate: N/A
Stream #0:0: Video: ansi, pal8, 640x400, 25 fps, 25 tbr, 25 tbn, 25 tbc
Stream mapping:
Stream #0:0 - #0:0 (ansi (native) - h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0x55b570ebc860] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x55b570ebc860] profile High 4:4:4 Predictive, level 3.0, 4:4:4 8-bit
[libx264 @ 0x55b570ebc860] 264 - core 152 r2854 e9a5903 - H.264/MPEG-4 AVC codec - Copyleft 2003-2017 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x1:0x111 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=4 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'test.mp4':
Metadata:
encoder : Lavf57.83.100
Stream #0:0: Video: h264 (libx264) (avc1 / 0x31637661), yuv444p, 640x400, q=-1--1, 25 fps, 12800 tbn, 25 tbc
Metadata:
encoder : Lavc57.107.100 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x55b570eb60c0] Auto-inserting h264_mp4toannexb bitstream filter
More than 1000 frames duplicated
[concat @ 0x55b570eac460] New audio stream 0:1 at pos:86369 and DTS:0.04s
More than 10000 frames duplicated 512kB time=00:06:27.24 bitrate= 10.8kbits/s dup=9725 drop=0 speed=53.2x
[ansi @ 0x55b570ebac40] Unknown escape code is not implemented. Update your FFmpeg version to the newest one from Git. If the problem still occurs, it means that your file has a feature which has not been implemented.
[ansi @ 0x55b570ebac40] If you want to help, upload a sample of this file to ftp://upload.ffmpeg.org/incoming/ and contact the ffmpeg-devel mailing list. (ffmpeg-devel@ffmpeg.org)
More than 100000 frames duplicated 6912kB time=01:06:27.24 bitrate= 14.2kbits/s dup=99590 drop=0 speed=53.7x
[mov,mp4,m4a,3gp,3g2,mj2 @ 0x55b570eb60c0] Auto-inserting h264_mp4toannexb bitstream filter929 drop=0 speed= 53x
frame=641090 fps=1312 q=-1.0 Lsize= 52592kB time=07:07:23.48 bitrate= 16.8kbits/s dup=640129 drop=0 speed=52.5x
video:45089kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 16.641100%
[libx264 @ 0x55b570ebc860] frame I:2822 Avg QP: 7.63 size: 10871
[libx264 @ 0x55b570ebc860] frame P:161554 Avg QP:24.00 size: 36
[libx264 @ 0x55b570ebc860] frame B:476714 Avg QP:32.95 size: 20
[libx264 @ 0x55b570ebc860] consecutive B-frames: 0.8% 0.0% 0.1% 99.0%
[libx264 @ 0x55b570ebc860] mb I I16..4: 88.8% 0.0% 11.2%
[libx264 @ 0x55b570ebc860] mb P I16..4: 0.0% 0.0% 0.0% P16..4: 0.1% 0.0% 0.0% 0.0% 0.0% skip:99.9%
[libx264 @ 0x55b570ebc860] mb B I16..4: 0.0% 0.0% 0.0% B16..8: 0.2% 0.0% 0.0% direct: 0.0% skip:99.8% L0:55.5% L1:44.5% BI: 0.0%
[libx264 @ 0x55b570ebc860] coded y,u,v intra: 10.2% 0.0% 0.0% inter: 0.0% 0.0% 0.0%
[libx264 @ 0x55b570ebc860] i16 v,h,dc,p: 95% 3% 1% 0%
[libx264 @ 0x55b570ebc860] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 31% 26% 21% 3% 4% 4% 4% 4% 3%
[libx264 @ 0x55b570ebc860] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x55b570ebc860] ref P L0: 99.4% 0.2% 0.3% 0.1%
[libx264 @ 0x55b570ebc860] ref B L0: 54.2% 43.5% 2.3%
[libx264 @ 0x55b570ebc860] ref B L1: 98.1% 1.9%
[libx264 @ 0x55b570ebc860] kb/s:14.40

(OPTIONAL) Finally, the third step is to remove frames that are not significantly different.
netto@bella:~/Desktop/video/rec126$ ffmpeg -i test.mp4 -vf mpdecimate test-2.mp4
ffmpeg version 3.4.6-0ubuntu0.18.04.1 Copyright (c) 2000-2019 the FFmpeg developers
built with gcc 7 (Ubuntu 7.3.0-16ubuntu3)
configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
WARNING: library configuration mismatch
avcodec configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared --enable-version3 --disable-doc --disable-programs --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libtesseract --enable-libvo_amrwbenc
avfilter configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared --enable-version3 --disable-doc --disable-programs --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libtesseract --enable-libvo_amrwbenc
libavutil 55. 78.100 / 55. 78.100
libavcodec 57.107.100 / 57.107.100
libavformat 57. 83.100 / 57. 83.100
libavdevice 57. 10.100 / 57. 10.100
libavfilter 6.107.100 / 6.107.100
libavresample 3. 7. 0 / 3. 7. 0
libswscale 4. 8.100 / 4. 8.100
libswresample 2. 9.100 / 2. 9.100
libpostproc 54. 7.100 / 54. 7.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'test.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf57.83.100
Duration: 07:07:23.60, start: 0.000000, bitrate: 16 kb/s
Stream #0:0(und): Video: h264 (High 4:4:4 Predictive) (avc1 / 0x31637661), yuv444p, 640x400, 14 kb/s, 25 fps, 25 tbr, 12800 tbn, 50 tbc (default)
Metadata:
handler_name : VideoHandler
Stream mapping:
Stream #0:0 - #0:0 (h264 (native) - h264 (libx264))
Press [q] to stop, [?] for help
[libx264 @ 0x55860a800aa0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX FMA3 BMI2 AVX2
[libx264 @ 0x55860a800aa0] profile High 4:4:4 Predictive, level 3.0, 4:4:4 8-bit
[libx264 @ 0x55860a800aa0] 264 - core 152 r2854 e9a5903 - H.264/MPEG-4 AVC codec - Copyleft 2003-2017 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x1:0x111 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=4 threads=12 lookahead_threads=2 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=3 b_pyramid=2 b_adapt=1 b_bias=0 direct=1 weightb=1 open_gop=0 weightp=2 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
Output #0, mp4, to 'test-2.mp4':
Metadata:
major_brand : isom
minor_version : 512
compatible_brands: isomiso2avc1mp41
encoder : Lavf57.83.100
Stream #0:0(und): Video: h264 (libx264) (avc1 / 0x31637661), yuv444p, 640x400, q=-1--1, 25 fps, 12800 tbn, 25 tbc (default)
Metadata:
handler_name : VideoHandler
encoder : Lavc57.107.100 libx264
Side data:
cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
More than 1000 frames duplicated 0kB time=00:00:13.64 bitrate= 0.0kbits/s dup=398 drop=0 speed=27.3x
More than 10000 frames duplicated 512kB time=00:06:27.28 bitrate= 10.8kbits/s dup=9725 drop=0 speed=36.8x
More than 100000 frames duplicated 6656kB time=01:06:27.28 bitrate= 13.7kbits/s dup=99590 drop=0 speed= 35x
frame=641089 fps=907 q=-1.0 Lsize= 50808kB time=07:07:23.44 bitrate= 16.2kbits/s dup=640129 drop=0 speed=36.3x
video:43304kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 17.326782%
[libx264 @ 0x55860a800aa0] frame I:2822 Avg QP: 6.93 size: 10995
[libx264 @ 0x55860a800aa0] frame P:161554 Avg QP:24.03 size: 29
[libx264 @ 0x55860a800aa0] frame B:476713 Avg QP:33.02 size: 18
[libx264 @ 0x55860a800aa0] consecutive B-frames: 0.8% 0.0% 0.1% 99.0%
[libx264 @ 0x55860a800aa0] mb I I16..4: 88.7% 0.0% 11.3%
[libx264 @ 0x55860a800aa0] mb P I16..4: 0.0% 0.0% 0.0% P16..4: 0.0% 0.0% 0.0% 0.0% 0.0% skip:100.0%
[libx264 @ 0x55860a800aa0] mb B I16..4: 0.0% 0.0% 0.0% B16..8: 0.0% 0.0% 0.0% direct: 0.0% skip:100.0% L0:39.3% L1:60.7% BI: 0.0%
[libx264 @ 0x55860a800aa0] coded y,u,v intra: 10.3% 0.0% 0.0% inter: 0.0% 0.0% 0.0%
[libx264 @ 0x55860a800aa0] i16 v,h,dc,p: 95% 3% 1% 0%
[libx264 @ 0x55860a800aa0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 30% 26% 20% 3% 4% 4% 5% 4% 4%
[libx264 @ 0x55860a800aa0] Weighted P-Frames: Y:0.0% UV:0.0%
[libx264 @ 0x55860a800aa0] ref P L0: 98.7% 0.4% 0.8% 0.2%
[libx264 @ 0x55860a800aa0] ref B L0: 59.2% 39.3% 1.5%
[libx264 @ 0x55860a800aa0] ref B L1: 86.2% 13.8%
[libx264 @ 0x55860a800aa0] kb/s:13.83

Applying this optional step, you might save some more bytes, as you can see below:
netto@bella:~/Desktop/video/rec126$ ls -lah
total 141M
drwxr-xr-x 2 netto netto 4,0K Jul 19 02:26 .
drwxrwxr-x 46 netto netto 92K Jul 19 01:13 ..
...
-rw-rw-r-- 1 netto netto 50M Jul 19 02:38 test-2.mp4 (with the optional step)
-rw-rw-r-- 1 netto netto 52M Jul 19 01:53 test.mp4 (without the optional step)