# ffmpeg -i input.mp4 -filter:v "scale=                                                                                              'if(gt(a,720/480),720,-1)':'if(gt(a,720/480),-1,480)',pad=w=720:h=480:x=(ow-iw)/                                                                                              2:y=(oh-ih)/2" -target ntsc-dvd out.mpg
ffmpeg version 1.0.8 Copyright (c) 2000-2013 the FFmpeg developers
  built on Sep 12 2013 11:54:40 with gcc 4.7 (Debian 4.7.2-5)
  configuration: --prefix=/usr --extra-cflags='-g -O2 -fstack-protector --param=                                                                                              ssp-buffer-size=4 -Wformat -Werror=format-security ' --extra-ldflags='-Wl,-z,rel                                                                                              ro' --cc='ccache cc' --enable-shared --enable-libmp3lame --enable-gpl --enable-n                                                                                              onfree --enable-libvorbis --enable-pthreads --enable-libfaac --enable-libxvid --                                                                                              enable-postproc --enable-x11grab --enable-libgsm --enable-libtheora --enable-lib                                                                                              opencore-amrnb --enable-libopencore-amrwb --enable-libx264 --enable-libspeex --e                                                                                              nable-nonfree --disable-stripping --enable-libvpx --enable-libschroedinger --dis                                                                                              able-encoder=libschroedinger --enable-version3 --enable-libopenjpeg --enable-lib                                                                                              rtmp --enable-avfilter --enable-libfreetype --enable-libvo-aacenc --disable-deco                                                                                              der=amrnb --enable-libvo-amrwbenc --enable-libaacplus --libdir=/usr/lib/i386-lin                                                                                              ux-gnu --disable-vda --enable-libbluray --enable-libcdio --enable-gnutls --enabl                                                                                              e-frei0r --enable-openssl --enable-libass --enable-libopus --enable-fontconfig -                                                                                              -enable-libfdk-aac --enable-libdc1394 --disable-altivec --disab  libavutil                                                                                                    51. 73.101 / 51. 73.101
  libavcodec     54. 59.100 / 54. 59.100
  libavformat    54. 29.104 / 54. 29.104
  libavdevice    54.  2.101 / 54.  2.101
  libavfilter     3. 17.100 /  3. 17.100
  libswscale      2.  1.101 /  2.  1.101
  libswresample   0. 15.100 /  0. 15.100
  libpostproc    52.  0.100 / 52.  0.100
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'input.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 1
    compatible_brands: isomavc1
    creation_time   : 2013-07-03 14:08:03
  Duration: 01:53:43.89, start: 0.000000, bitrate: 2079 kb/s
    Stream #0:0(und): Video: h264 (High) (avc1 / 0x31637661), yuv420p, 1920x816,                                                                                               1979 kb/s, 23.98 fps, 23.98 tbr, 24k tbn, 47.95 tbc
    Metadata:
      creation_time   : 2013-07-03 14:08:03
      handler_name    : video.264#trackID=1:fps=23.976 - Imported with GPAC 0.5.                                                                                              0-rev
    Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 48000 Hz, stereo, s16, 95                                                                                               kb/s
    Metadata:
      creation_time   : 2013-07-03 14:08:10
      handler_name    : GPAC ISO Audio Handler
File 'out.mpg' already exists. Overwrite ? [y/N] y
Error when evaluating the expression 'if(gt(a,720/480),-1,480)'.
Maybe the expression for out_w:'if(gt(a,720/480),720,-1)' or for out_h:'if(gt(a,                                                                                              720/480),-1,480)' is self-referencing.
[Parsed_scale_0 @ 0xa0c4780] Failed to configure output pad on Parsed_scale_0
Error opening filters!