I suspect the audio is Dolby…Premiere wont import that format, nor will Audition. A DVD ripping app like IamToo can rip both audio and video from a DVD into a different format that can be edited, but there will be 2 additional generational losses in quality.
Playing the DVD in Windows Media Player and recording the audio in Audition will result in a quality audio file without generation losses to the video.
Best bet is to capture both audio and video from the camera via an analog/digital converter as digital video…spend the $ on hardware solution, not software…like the ADS Pyro A/V link or Canopus ADVC 100.