CHDK firmware hack discussion (19)

Started Oct 18, 2007 | Discussions thread
mx32 New Member • Posts: 22
Motion Detection code investigation

main purpose of investigation : decrease time between detection and shot

investigation results:

1) there are 3 frames(buffers) with live "video" data which are prepared for display on LCD ( one of them is used for MD/Zebra/Histogram)
2) each of them is updated every 100 msecs.
3) they are sequentially updated periodically every
so first 30 msecs OS updates first frame(buffer)
next 30msecs - second buffer
next 30 msecs - third buffer
and so on again

so summary it gives 30 frames per second - seems ok for LCD display.


1) any build which uses last code of MD uses only one of three buffers so it leads to minimal detection time: ~ 100 msecs

2) at first stage of MD code improving it is possible to decrease detection time from 100 msecs to 30 msecs.
i have already done it to my a630.
it is required to analyze FW for other camera models to make such adjustments.

3) no frames acquired from sensor when LCD is switched off.

  • it is possible to acquire frames from sensor while LCD is off (needs allot of investigation)

4) also using of ubasic command "shot" takes about 80 msecs (at minimum) to actually make a shot ( camera executes some algorithms to adjust to scene ).
using of [click "shot_full"] can reduce these 80+ msecs to 20-30 msecs.

it is possible to decrease this time to zero using some native "MakeShot" function (again it needs allot of investigation of FW [for every camera!])

I hope I will be able soon publish more detailed investigation results on wiki for owners of other camera models to find out what changes must be applied to code

It seems there are not much people who would be interested in decreasing of motion detection time so I am not going to rush and not sure there is a need for any improvements....

waiting for comments....

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