ffmpeg stream sequence.

 ./ffmpeg201 -y -analyzeduration 50M -i /tmp/BE9BE28C97.mp4 -analyzeduration 50M -i C.mpg  -filter_complex '[0:0] [0:1] [1:0] [1:1] concat=n=2:v=1:a=1 [v] [a], [v] setsar=1/1, setdar=4/3 [v]' -map '[v]' -map '[a]' -s 640x480 -vcodec libx264 -b:v 15M -maxrate 20M -bufsize 5M -pix_fmt yuv420p -threads 0 -c:a libfaac -b:a 320k test5.mp4


ffmpeg version 2.0.1 Copyright (c) 2000-2013 the FFmpeg developers
  built on Sep  3 2013 11:54:23 with gcc 4.1.2 (GCC) 20080704 (Red Hat 4.1.2-52)
  libavutil      52. 38.100 / 52. 38.100
  libavcodec     55. 18.102 / 55. 18.102
  libavformat    55. 12.100 / 55. 12.100
  libavfilter     3. 79.101 /  3. 79.101
  libswscale      2.  3.100 /  2.  3.100
  libswresample   0. 17.102 /  0. 17.102
  libpostproc    52.  3.100 / 52.  3.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from '/tmp/BE9BE28C97.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2avc1mp41
    encoder         : Lavf55.12.100
  Duration: 00:00:12.01, start: 0.021333, bitrate: 40 kb/s
    Stream #0:0(eng): Video: h264 (High 4:4:4 Predictive) (avc1 / 0x31637661), yuv444p, 720x480 [SAR 8:9 DAR 4:3], 27 kb/s, 29.97 fps, 29.97 tbr, 30k tbn, 59.94 tbc
    Metadata:
      handler_name    : VideoHandler
    Stream #0:1(und): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 3 kb/s
    Metadata:
      handler_name    : SoundHandler
Input #1, mpeg, from 'C.mpg':
  Duration: 00:00:36.67, start: 0.261811, bitrate: 18121 kb/s
    Stream #1:0[0x80]: Audio: ac3, 48000 Hz, stereo, fltp, 384 kb/s
    Stream #1:1[0x1e0]: Video: mpeg2video (4:2:2), yuv422p, 720x480 [SAR 8:9 DAR 4:3], 29.97 fps, 29.97 tbr, 90k tbn, 59.94 tbc
Stream specifier ':0' in filtergraph description [0:0] [0:1] [1:0] [1:1] concat=n=2:v=1:a=1 [v] [a], [v] setsar=1/1, setdar=4/3 [v] matches no streams.