dropped frames

[JamesF]

A little test I've just done with my Logitech 4000 (dayight and I've tried to standardise the brightness of what it was pointing at).

Left the sharpcap settings the same (640x480, RGB24, 1/100th second exposures, 20 second video runs); run at 5, 10, 15, 20, 25, 30 fps, each one three times. Taken the average (not scientific I know) of each these, and the number of dropped frames each time. The percentage of dropped frames seems similar (if anything less at 30fps (which was a highly reproducible feature)), and the file size divided by the number of frames in each video was similar, which surprised me, as I'd expected to see a fall in this as compression kicked in. So, I'm not a lot wiser after my experiment, but hopefully one of the clever guys will expalin it or pull my scientific method to shreads

There are probably quite a few other variables here.  I'm not entirely sure where to start in terms of explaining all of it.  However, RGB24 is the format of the data in the output file, not (necessarily) the format of the data as transferred from the camera so if all the files are written in the same format then I'd expect the ratio of the number of frames to file size to be broadly similar in all respects.

James

[allcart]

good explanation James. I'm glad some folks understand the inner workings of cameras, coz I sure don't.

[pipsquip]

Looking at all your replies has made me wonder the cable I got with the imager was to short so I have got a 5 meter cable could part of the problem be the cable

[JamesF]

5m is within the USB spec as far as I recall, but right at the limit.  If something is a bit marginal then a shorter cable may help.

James

[pipsquip]

I dropped the frame rate to 10fps and my dropped frames have gone from 70% to less than 10% . The 5 meter cable I have got is only a very cheap one I might invest in a better cable and see what happens