transcode to dvd using ffmpeg dvdauthor and growisofs

* transcode

  ffmpeg -i input.asf -target pal-dvd output.mpg
                                                                                                                                     
* Now you can use this file to make a DVD:

  export VIDEO_FORMAT=NTSC # NTSC or PAL
  dvdauthor -t -o youroutputdirectory -f output.mpg
  dvdauthor -o youroutputdirectory                                      
  mkisofs -dvd-video -o dvdimage.iso youroutputdirectory
  growisofs -speed=4 -dvd-compat -Z /dev/dvd=dvdimage.iso
                                                                                                             
* Verify by comparing MD5SUM

  md5sum dvdimage.iso 
  ISOSIZE=$(( $(ls -l dvdimage.iso | awk '{ print $5 }') / 2048 ))
  dd if=/dev/dvd bs=2048 count=${ISOSIZE} | md5sum

from http://ubuntuforums.org/showthread.php?t=1123447