I just ran into this today after using iMovie (10.1.10 on macOS 10.4.3) to import 7 miniDV tapes on a Canon Elura 100 (same camera for recording and playback) via firewire 400 on a MacPro. After reviewing my fine work, I realized that only the recording from the first tape had audio imported. There's nothing wrong with the camera or any tapes as audio plays correctly through the camera's speakers and I'm sure no recording settings changed between tapes.
Here's where it gets strange. I checked one of the "bad" tapes with QuickTime Player (File > New Movie Recording) and started playback manually with the camera controls. I could see the audio monitor registering audio input in the monitor window, but no sound was output to my speakers. However, from the video monitor window (without recording started), if I click the triangle arrow next to the record button and switch "Quality" from "HIgh" to "Maximum" (or vice-versa if Maximum is already selected), all of a sudden audio starts being played through my computer speakers. Any recordings I do after this starts work capture audio correctly.
So there seems to be a legitimate, OS-level bug with firewire audio capture. Maybe something isn't initialized properly until the quality setting is toggled. Nevertheless, it seems if audio isn't captured correctly from the start, the resulting files are useless. Now I just have to figure out how to get iMovie working consistently.
Here's where it gets strange. I checked one of the "bad" tapes with QuickTime Player (File > New Movie Recording) and started playback manually with the camera controls. I could see the audio monitor registering audio input in the monitor window, but no sound was output to my speakers. However, from the video monitor window (without recording started), if I click the triangle arrow next to the record button and switch "Quality" from "HIgh" to "Maximum" (or vice-versa if Maximum is already selected), all of a sudden audio starts being played through my computer speakers. Any recordings I do after this starts work capture audio correctly.
So there seems to be a legitimate, OS-level bug with firewire audio capture. Maybe something isn't initialized properly until the quality setting is toggled. Nevertheless, it seems if audio isn't captured correctly from the start, the resulting files are useless. Now I just have to figure out how to get iMovie working consistently.