Matt – according to page 89
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Matt – according to page 89 of the manual for the XA20 and XA25:
"When you are monitoring the audio, you can choose to synchronize the audio signal with the video signal or monitor the audio in real time. Use the [Monitor Delay] setting to select the method. Note that there will be a slight delay when you monitor in real time. Regardless of the setting, however, the audio and video signals recorded will be synchronized."
I have this same feature on my Panasonic GH3. It allows you to hear either what the camera is "hearing" (delayed) – or what the camera has already recorded (no delay).
This can be useful in determining whether the source of an audio issue is external or internal to the camera, but I never use it – it's too distracting.
What amazes me is that Canon Tech Support clearly hadn't read the manual! I hope you didn't have to pay for that call 🙂
Hope this is helpful,
Bill