ffmpeg -i The.Last.Boy.Scout.1991.1080p.mkv -vf scale=320:-1 -codec:v prores_ks -profile:v 1 -pix_fmt yuv422p10le -qscale:v 11 -codec:a pcm_s16le -ac 2 -ar 48000 newprores.mov

ffmpeg version 2.5.4 Copyright (c) 2000-2015 the FFmpeg developers
  built on Feb 13 2015 17:05:44 with gcc 4.9.2 (GCC) 20150204 (prerelease)
  configuration: --prefix=/usr --disable-debug --disable-static --disable-stripping --enable-avisynth --enable-avresample --enable-fontconfig --enable-gnutls --enable-gpl --enable-libass --enable-libbluray --enable-libfreetype --enable-libfribidi --enable-libgsm --enable-libmodplug --enable-libmp3lame --enable-libopencore_amrnb --enable-libopencore_amrwb --enable-libopenjpeg --enable-libopus --enable-libpulse --enable-librtmp --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libv4l2 --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libx265 --enable-libxvid --enable-runtime-cpudetect --enable-shared --enable-swresample --enable-vdpau --enable-version3 --enable-x11grab
  libavutil      54. 15.100 / 54. 15.100
  libavcodec     56. 13.100 / 56. 13.100
  libavformat    56. 15.102 / 56. 15.102
  libavdevice    56.  3.100 / 56.  3.100
  libavfilter     5.  2.103 /  5.  2.103
  libavresample   2.  1.  0 /  2.  1.  0
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
Input #0, matroska,webm, from 'The.Last.Boy.Scout.1991.1080p.mkv':
  Metadata:
    encoder         : libebml v1.2.3 + libmatroska v1.3.0
    creation_time   : 2013-03-16 12:35:32
  Duration: 01:45:25.95, start: 0.000000, bitrate: 11348 kb/s
    Stream #0:0(eng): Video: h264 (Main), yuv420p(tv, bt709), 1920x800, SAR 1:1 DAR 12:5, 23.98 fps, 23.98 tbr, 1k tbn, 180k tbc (default)
    Stream #0:1(eng): Audio: dts (DTS), 48000 Hz, 5.1(side), fltp, 1536 kb/s (default)
Output #0, mov, to 'newprores.mov':
  Metadata:
    encoder         : Lavf56.15.102
    Stream #0:0(eng): Video: prores (prores_ks) (apcs / 0x73637061), yuv422p10le, 320x133 [SAR 399:400 DAR 12:5], q=2-31, 200 kb/s, 23.98 fps, 24k tbn, 23.98 tbc (default)
    Metadata:
      encoder         : Lavc56.13.100 prores_ks
    Stream #0:1(eng): Audio: pcm_s16le (sowt / 0x74776F73), 48000 Hz, stereo, s16, 1536 kb/s (default)
    Metadata:
      encoder         : Lavc56.13.100 pcm_s16le
Stream mapping:
  Stream #0:0 -> #0:0 (h264 (native) -> prores (prores_ks))
  Stream #0:1 -> #0:1 (dts (dca) -> pcm_s16le (native))
Press [q] to stop, [?] for help
frame=151648 fps=243 q=11.0 Lsize= 2331806kB time=01:45:25.95 bitrate=3019.6kbits/s
video:1143592kB audio:1186116kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.090042%