hopper@hopper-xubuntu:~$ ffmpeg -f v4l2 -video_size 640x480 -framerate 30 -vcodec mjpeg -i /dev/video0 -video_size 640x480 -framerate 30 -vcodec mjpeg -i /dev/video1 -framerate 30 -filter_complex hstack -threads 0 -c:v libx264 -preset veryfast outputsplit.ts
ffmpeg version 2.8.11-0ubuntu0.16.04.1 Copyright (c) 2000-2017 the FFmpeg developers
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
  configuration: --prefix=/usr --extra-version=0ubuntu0.16.04.1 --build-suffix=-ffmpeg --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --cc=cc --cxx=g++ --enable-gpl --enable-shared --disable-stripping --disable-decoder=libopenjpeg --disable-decoder=libschroedinger --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-libmodplug --enable-libmp3lame --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --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-libxvid --enable-libzvbi --enable-openal --enable-opengl --enable-x11grab --enable-libdc1394 --enable-libiec61883 --enable-libzmq --enable-frei0r --enable-libx264 --enable-libopencv
  libavutil      54. 31.100 / 54. 31.100
  libavcodec     56. 60.100 / 56. 60.100
  libavformat    56. 40.101 / 56. 40.101
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 40.101 /  5. 40.101
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  2.101 /  1.  2.101
  libpostproc    53.  3.100 / 53.  3.100
[video4linux2,v4l2 @ 0x1bcc740] The driver changed the time per frame from 1/30 to 513/61612
[mjpeg @ 0x1bcd460] Changeing bps to 8
Input #0, video4linux2,v4l2, from '/dev/video0':
  Duration: N/A, start: 114.753946, bitrate: N/A
    Stream #0:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 640x480, -21 kb/s, 120.10 fps, 120.10 tbr, 1000k tbn, 1000k tbc
[mjpeg @ 0x1bcfb20] Changeing bps to 8
Input #1, video4linux2,v4l2, from '/dev/video1':
  Duration: N/A, start: 115.166332, bitrate: N/A
    Stream #1:0: Video: mjpeg, yuvj422p(pc, bt470bg/unknown/unknown), 640x480, -5 kb/s, 30 fps, 30 tbr, 1000k tbn, 1000k tbc
File 'outputsplit.ts' already exists. Overwrite ? [y/N] y
No pixel format specified, yuvj422p for H.264 encoding chosen.
Use -pix_fmt yuv420p for compatibility with outdated media players.
[libx264 @ 0x1bd36a0] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2
[libx264 @ 0x1bd36a0] profile High 4:2:2, level 4.2, 4:2:2 8-bit
Output #0, mpegts, to 'outputsplit.ts':
  Metadata:
    encoder         : Lavf56.40.101
    Stream #0:0: Video: h264 (libx264), yuvj422p(pc), 1280x480, q=-1--1, 120.10 fps, 90k tbn, 120.10 tbc (default)
    Metadata:
      encoder         : Lavc56.60.100 libx264
Stream mapping:
  Stream #0:0 (mjpeg) -> hstack:input0
  Stream #1:0 (mjpeg) -> hstack:input1
  hstack -> Stream #0:0 (libx264)
Press [q] to stop, [?] for help
[video4linux2,v4l2 @ 0x1bcc740] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
[video4linux2,v4l2 @ 0x1bcf040] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
Past duration 0.930107 too large
Past duration 0.969048 too large     191kB time=00:00:00.18 bitrate=8563.6kbits/s
Past duration 0.654655 too large
Past duration 0.623222 too large
Past duration 0.640312 too large
Past duration 0.680473 too large
Past duration 0.773613 too large
Past duration 0.826408 too large
Past duration 0.864067 too large
Past duration 0.923637 too large
Past duration 0.898125 too large     356kB time=00:00:00.60 bitrate=4800.4kbits/s
frame=  117 fps= 58 q=-1.0 Lsize=     599kB time=00:00:02.61 bitrate=1875.4kbits/s
video:541kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 10.549138%
[libx264 @ 0x1bd36a0] frame I:1     Avg QP:22.76  size: 57135
[libx264 @ 0x1bd36a0] frame P:42    Avg QP:27.32  size: 11124
[libx264 @ 0x1bd36a0] frame B:74    Avg QP:27.87  size:   406
[libx264 @ 0x1bd36a0] consecutive B-frames: 11.1%  8.5% 15.4% 65.0%
[libx264 @ 0x1bd36a0] mb I  I16..4: 33.9% 25.0% 41.2%
[libx264 @ 0x1bd36a0] mb P  I16..4:  1.5%  5.1%  1.5%  P16..4: 31.5%  5.8%  3.0%  0.0%  0.0%    skip:51.5%
[libx264 @ 0x1bd36a0] mb B  I16..4:  0.1%  0.1%  0.0%  B16..8:  2.1%  0.3%  0.0%  direct: 3.4%  skip:94.0%  L0:42.4% L1:50.9% BI: 6.7%
[libx264 @ 0x1bd36a0] 8x8 transform intra:54.0% inter:63.5%
[libx264 @ 0x1bd36a0] coded y,uvDC,uvAC intra: 59.3% 72.0% 29.1% inter: 5.9% 12.4% 1.1%
[libx264 @ 0x1bd36a0] i16 v,h,dc,p: 60% 27%  7%  7%
[libx264 @ 0x1bd36a0] i8 v,h,dc,ddl,ddr,vr,hd,vl,hu: 16% 37% 26%  3%  3%  3%  5%  3%  5%
[libx264 @ 0x1bd36a0] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 23% 30% 12%  4%  5%  7%  7%  5%  7%
[libx264 @ 0x1bd36a0] i8c dc,h,v,p: 49% 24% 21%  5%
[libx264 @ 0x1bd36a0] Weighted P-Frames: Y:4.8% UV:2.4%
[libx264 @ 0x1bd36a0] kb/s:1664.59
Exiting normally, received signal 2.