Mini DV DVAVI files are streamed ( that is why it is a real time process) . This involves transferring huge amounts of data fairly quickly and anything that interrupts the process will result in dropped frames.
The usb transfer of mpeg2 files from HDD camcorder is rather a different matter and not directly comparable.
Dropped frames could be anything from a faulty firewire cable, to a poorly performing capture HDD ( or system)
It is often recommended that video capture be to another hard drive, or anther partition different from the System partition.
Whichever the capture drive, being fragmented is a major culprit, as are disc errors. Defragment your capture HDD if applicable)
Sometimes, if there are too many programs running in the background, ( anti virus, anti spyware ect) or you chose to start multitasking during capture, dropped frames may happen.
In the past, small amount of ram was easily the culprit but most systems lately have enough
Very occasionally , the capture program may be corrupt: try capturing with Nero ( if you have it, or
WINDV)
HTH
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