To output a file to DVD from MythTV.

Bring up a command prompt by pressing Ctrl+Alt+Enter.
Type in:

cd /media/dvd

nuvexport-dvd –nice=4

This will prompt you as to which recordings you want outputted.  Select a recording by typing in the relevant number beside its name.  If you wish to do more than one program, press ‘n’ to take you back to the program select screen.  When you’ve selected all the programs you want it to prepare, press c to continue.  I’d suggest just going with the default options, except for denoise.  Make sure you say no to denoise as its unnecessary on a digital signal and will just make the process a lot slower.  To go with the default options (shown in square brackets) just press enter.  
This process will take time depending on the amount of work to do, so set it up and leave it running.  A fair estimate is that it takes about 25 minutes to process 30 minutes of a recorded program.
What you should now find is that nuvexport has created a series of mpg files.  To see what files have been created type in:

ls

This should list one mpg per program you’ve just processed.
Once it has finished type in the following command, replacing “movie.mpg” with a relevant file name from the list you’ve just seen¹.

dvdauthor -o dvdout/ -t movie.mpg

Repeat the last command, substituting the relevant file names for each clip you want to have on the DVD, the type in the following command to finish preparing the content:

dvdauthor -o dvdout/ -T

To burn the files to a DVD, type in the following command, replacing “<volumelabel>” with an appropriate name:

growisofs -Z /dev/cdrom -dvd-video -V <volumelabel> dvdout/

If you are finished and don’t wish to make another copy of the DVD, and type in the final command:

rm –R dvdout/*


¹ Handy Hint:  Linux likes to help you with file names.  When you’ve typed in “-t ” (including the space afterwards) of the dvdauthor command, press the tab key twice.  A list of all the files in your current directory will appear.  You can also use tab to autocomplete the filename, just type in the first few characters and press tab. If that doesn’t complete it all (including the .mpg at the end) you’ve probably got two similarly named files.  Press tab twice to show those files, then complete the filename manually.
NB: Linux is case sensitive with filenames.