We don't know yet how the US wants to transfer the men, whether on one flight - which would have enormous symbolic value to British ministers - or separately and with no fanfare.
Transcoding occurs at 1:1 speed, meaning an hour of footage will take an hour of processing, but you do have the option of converting your videos immediately after they're recorded, so they're prepped before you need to run out the door to catch a flight (the actual wireless transfer takes between five and eight minutes for each hour-long show).