ffmpeg two videos muxing side by side

$ ffmpeg -report -i presenter.mp4 -i screen.mp4 -filter_complex \
> "[1:v]pad=iw*2:ih[bg];[bg][0:v]overlay=W/2+((W/2-w)/2):(H-h)/2" \
> -qscale:v 2 final-video-sbs.mp4
ffmpeg started on 2014-09-21 at 23:57:42
Report written to "ffmpeg-20140921-235742.log"
ffmpeg version 2.4 Copyright (c) 2000-2014 the FFmpeg developers
  built on Sep 15 2014 01:02:34 with gcc 4.8 (Ubuntu 4.8.2-19ubuntu1)
  configuration: --extra-libs=-ldl --prefix=/opt/ffmpeg --enable-avresample --disable-debug --enable-nonfree --enable-gpl --enable-version3 --enable-x11grab --enable-libpulse --enable-libopencore-amrnb --enable-libopencore-amrwb --disa$
  libavutil      54.  7.100 / 54.  7.100
  libavcodec     56.  1.100 / 56.  1.100
  libavformat    56.  4.101 / 56.  4.101
  libavdevice    56.  0.100 / 56.  0.100
  libavfilter     5.  1.100 /  5.  1.100
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  0.100 /  3.  0.100
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  0.100 / 53.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'presenter.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf56.4.101
  Duration: 00:36:16.22, start: 0.000000, bitrate: 3002 kb/s
    Stream #0:0(und): Video: h264 (Constrained Baseline) (avc1 / 0x31637661), yuvj420p(pc), 1920x1080 [SAR 1:1 DAR 16:9], 3001 kb/s, 15.54 fps, 30 tbr, 15360 tbn, 60 tbc (default)
    Metadata:
      handler_name    : VideoHandler
Input #1, mov,mp4,m4a,3gp,3g2,mj2, from 'screen.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf56.4.101
  Duration: 00:34:22.27, start: 0.000000, bitrate: 143 kb/s
    Stream #1:0(und): Video: h264 (High 4:4:4 Predictive) (avc1 / 0x31637661), yuv444p, 1920x1080, 140 kb/s, 30 fps, 30 tbr, 15360 tbn, 60 tbc (default)
    Metadata:
      handler_name    : VideoHandler
[swscaler @ 0x1dd4a60] deprecated pixel format used, make sure you did set range correctly
[libx264 @ 0x1976220] -qscale is ignored, -crf is recommended.
[libx264 @ 0x1976220] using cpu capabilities: MMX2 SSE2Fast LZCNT
[libx264 @ 0x1976220] profile High, level 5.0
[libx264 @ 0x1976220] 264 - core 142 r2431 ac76440 - H.264/MPEG-4 AVC codec - Copyleft 2003-2014 - http://www.videolan.org/x264.html - options: cabac=1 ref=3 deblock=1:0:0 analyse=0x3:0x113 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_r$
Output #0, mp4, to 'final-video-sbs.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf56.4.101
    Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 3840x1080, q=-1--1, 30 fps, 15360 tbn, 30 tbc (default)
    Metadata:
      encoder         : Lavc56.1.100 libx264