change GetFrameNumber into GetBlockID
stream data from 3 cameras into ssd.
i'm not sure if the ssd is too slow

 2151 be/4 martin      0.00 B/s  218.20 M/s  0.00 %  0.00 % sbcl --dynamic-space-size 16000
slow acquisition down a little bit
 4042 be/4 martin      0.00 B/s  112.72 M/s  0.00 %  0.00 % sbcl --dynamic-space-size 16000
add some results from the discussion with Hauke