If you want to get myth2ipod working on Ubuntu (assuming you have both MythTV and Ubuntu installed) there aren’t any instructions to my knowledge. I found the currently posted set of instructions to be outdated (last update 3/5/06). The following, updated instructions are actually much simpler (everything is in apt).

I did as follows (Myth .20, Ubuntu 7.04):

1. Get the appropriate version of ffmpeg (with xvid support). To do that, add this line to your /etc/apt/sources.list file:
   deb http://packages.medibuntu.org/ feisty free non-free
   and then run
   wget -q http://packages.medibuntu.org/medibuntu-key.gpg -O- | sudo apt-key add - && sudo apt-get update
   Then install your brand new version of ffmpeg:
   sudo apt-get install ffmpeg
   (found that tip linked from here)
2. To test what you did in step 1, run ffmpeg -version and make sure you see ‘enable-xvid’ and ‘enable-faac’ in the output.
3. Install the codec library, which is required to make sure you can encode aac audio.
   sudo apt-get install libavcodec0d
   To test that you can, run ffmpeg -formats and make sure you see DEA aac listed under “Codecs”.
4. Install mp4box, which is available in apt under ‘gpac’ sudo apt-get install gpac
5. Grab nuvexport:
   cd /tmp
   wget http://forevermore.net/files/nuvexport-latest.tar.bz2
   tar -xjvf nuvexport-latest.tar.bz2
   sudo mv nuvexport-0.4 /usr/local/share/nuvexport

6. Copy down the scripts and put them in the right places:
cd /tmp
wget http://myth2ipod.com/myth2ipod.txt
wget http://myth2ipod.com/iPod.pm
sudo mv myth2ipod.txt /usr/local/bin/myth2ipod
sudo chmod +x /usr/local/bin/myth2ipod
sudo mv iPod.pm /usr/local/share/nuvexport/export/ffmpeg/iPod.pm
sudo ln -s /usr/local/share/nuvexport/nuvexport /usr/local/bin/nuvexport

7. At this point you can follow the rest of the instructions at the site for editing /usr/local/bin/myth2ipod , etc. The rest of it is not distribution-specific. The slight change I had to make was the path to MP4Box which is hard-coded in the script to point to /usr/local/bin but on Ubuntu it gets put into /usr/bin.