Isochronous mode is unrelated to whether you use a hard drive. Isochronous versus block mode depends on your camera’s USB design. If the camera states it wants to use block mode, then it behaves similar to a hard drive with stop/start.
If you run “lsusb -t”, you will see some lines end with one of these: “1.5M”, “12M”, “480M”, or “5000M”. Those are speeds devices are running at in units of Mbit/sec. At least in the case of one root HUB, you should see “5000M”…if not you probably didn’t update the kernel parameter to allow it to operate at 5000Mbit/sec. Any device plugged into that HUB would also be limited by root HUB speed, and if it doesn’t run at 5000M, the next speed lower is 480M. This is the basic USB setting for its speed.
A device has its own speed and operating mode. If you simply run “lsusb”, with no options, you should see an entry which is your camera. There is an “ID” listed for that particular device which can be used to select just that device under lsusb. The “-d” parameter of lsusb accepts that ID to pick just that device. For example, I have a mouse which shows up as ID “1b1c:1b05”, so I could list just the mouse as:
lsusb -d '1b1c:1b05'
The reason for using the ID is because you wouldn’t want to use verbose lsusb output of all devices at once. Assuming your ID is edited to something other than my mouse, you could list all USB attributes in verbose mode via:
lsusb -d '1b1c:1b05' -v
# or...for paging...
lsusb -d '1b1c:1b05' -v | less
# or...for logging to a file...
lsusb -d '1b1c:1b05' -v | tee usb_log.txt
Typically you would search that verbose lsusb for “Transfer Type” and see either “Isochronous” or “Bulk” on your camera (keep in mind there are multiple components to a USB device…not all have to be in the same mode, but at least the camera must be isochronous to be guaranteed no stop/start behavior).
Does your camera show isochronous mode or bulk mode? Does your lsusb -t show 5000M for your camera?