       --export_prof S
              Valid  values  for S are vcd, vcd-pal, vcd-ntsc, svcd, svcd-pal,
              svcd-ntsc, dvd, dvd-pal and dvd-ntsc.
                                                                                
     When one of the above is  used,  transcode  will  calculate  the
              needed  clipping and resizing values for you based on the import
              and export aspect ratio. This is especially handy if you want to
              encode a 16:9 DVD into a 4:3 SVCD for example.  Transcode inter-
              nally then sets --pre_clip to add the  black  bars  ("letterbox-
              ing").
          If  you  use "vcd" instead of "vcd-pal" or "vcd-ntsc", transcode
              will make an educated guess if PAL or NTSC vcd  is  wanted.  The
              same  is  true  for "svcd" and "dvd". When the input file has no
              aspect ratio information at all, transcode guesses it  based  on
              the  import  frame sizes. You can set the import aspect ratio by
              giving --import_asr CODE.

       --keep_asr
              try to keep aspect ratio (only with -Z) [off]
              The --keep_asr options changes the meaning of -Z.  It  tries  to
              fit  the  video  into a framesize specified by -Z by keeping the
              original aspect ratio.
