Many cards have four or even more inputs. Anyway a single bt chip (a
single device) can handle up to four inputs with a multiplexer.
When an input is selected, you can gain a framerate of 25 fps (PAL).
I must acquire images from multiple cameras (at least two) continuosly.
Does anybody know hot to get the best framerate per input (ideally 25/4
fps less switch time) grabbing sequentially from all the avaiable
channels?
With the following mode I can achieve only 4 fps per camera (with 2
cameras):
while (1) {
switchInput(0)
read();
... (process image)
switchInput(1)
read()
... (process image)
}
With the following mode (memory mapped buffers) I can achieve 12 fps per
camera, but the images are corrupted (contains informations from more
than a single camera) when using more than 1 buffer, and using 1 buffer
the result is tipically the same as reading with read():
while (1) {
dqbuf();
... (process image)
switchInput(1)
qbuf();
dqbuf();
... (process image)
switchInput(0)
qbuf();
}
I've tried inserting some usleep(), from 10 to 80 msec, in different
places, in order to synchronize, but there are corrupted images anyway.
I repeat, many cards have four inputs, so I suppose that will exist a
method to grab from multiple cameras and gain a real-time framerate.
Thanks,
Fabrizio Cornelli and Sandro Bosio
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