From this, the minimum prefocus period was 680ms, the maximum 770ms and the subsequent period until the hook_shoot was ready was constant at 140ms on all 8 cameras.
Quote from: reyalp on 22 / September / 2017, 17:31:16and there's some hand-off time between the usb code and the script seeing it (~10s of ms).Is there another way of saying the same thing - I can't quite picture the context.
and there's some hand-off time between the usb code and the script seeing it (~10s of ms).
I'm curious if there might be a way to reduce the time by breaking down a large number of cameras in smaller groups. Of course one would have to work out a method to sync the groups so perhaps its not possible ... ?
The hand-off time I referred to is the time the message spends sitting in the queue.
I meant if the sync time becomes too great with a large number of cameras, would it be possible to parallel process with smaller groups simultaneously, so a higher process would determine when all the groups were sync'd?
In theory, yeah. If you had multiple, separate systems running multicam which you could command simultaneously, then the amount of time required to send commands to or receive responses from them would reduced proportional to the number of cameras connected to a single system. I suspect implementation would be complicated though.
FWIW, the USB remote code includes a function called kbd_calibrate_synch_delay( ). That function must be used during CHDK development to calibrate an internal constant named synch_delay_tick . The default value if no calibration is done is just a wild guess of an appropriate starting value, and the actual delay that occurs will change with ARM CPU model and clock speed.AFAIK, the calibration function has never been used and every camera defaults to the same calibration value. In fact, as built today, the value is in part of the CHDK source code that is common to every camera. There is no way to set it up on a per camera basis. So you options are to enable the function in source and calibrate yourself for your personal build. Or, just experiment with the Synch Delay [ ] value. Set it to 5000 and measure the delay created from shutter release. Adjust the value until you get five seconds. Calculate the multiplier necessary to calibrate the value. Then multiply your 420 value by that factor. Done.
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