I am now trying to import some old tapes and have run into the same problem, but weirder. Of 15 MiniDV tapes, 7 have imported successfully with sound while the other 8 have picture, but no sound. I have adjusted and eliminated every possible variable I can think of.
- The tapes were all shot on (and are playing back from) the same Canon camcorder.
- I am using a new Firewire cable in to an Apple Thunderbolt adapter, straight into the Mac.
- I am using iMovie, which has no problem recognising and controling the camera for import (the camera is not on the 'supported' list, but, as I say, half of the tapes have imported fine.)
- I have used a head cleaning tape between each of the 15.
- The sound is fine on the tape if I just play back one of the 'problem' tapes on the camcorder.
- I have restarted the Mac, tried writing to internal and external drives, set up new libraries, set up as a different user etc.
- I have tried the 'good tapes' again, and they still import fine so nothing seems to have changed on the Mac (I was thinking corrupt preference file for example)
- Playing the imported files in Quicktime is the same, some just don't have sound. Similarly you can se in iMovie if an audio waveform is present or not.
A complete mystery! Does anyone have any other suggestions - or similar experience? Otherwise, I guess the next step is to send off all the tapes to a specialist transfer company.