Download MakeMKV and rip the DVD to an MKV by selecting the main title and audio track that you want to keep. This will keep the original video and audio, but put them in a container that is easier to work with in JRiver.
- Import the mkv into JRiver.
- Use the instructions on JRiver's wiki for creating Particles for individual songs (see below for alternate method). The wiki uses a Blu-ray as an example, but it will also work for an MKV. It won't work for the original DVD structure which is why I had you rip to an MKV.
- Select all the Particles you created, right click, select Library Tools > Convert Format
- In the Convert Format action windows, check "Convert video to audio"
- Select the encoder you want to use such as FLAC
- Click Option in the Convert Format action window
- Set your file location, click "Leave original file; add destination file . . .", set "Number of files to convert . . ." to 1
- Click OK and then Convert
JRiver will now make an audio file for each Particle. After conversion your files should be already imported and ready to view in the Audio views.
I just went through the entire process including downloading MakeMKV and it took about 15 minutes. I only created one Particle, though. Instead of creating multiple Particles, you can just change the playback range tag for the imported video and keep selecting Convert Format after updating the playback range. I think this method can be faster if you don't want the Particles also imported into your library.