Capturing Images Using System Buffers

The following code example asks the device driver to use system buffers and registers a callback which gets called on the arrival of each new frame:

Remarks:

To activate system buffers, set the buffer_type field of the video format to UNICAP_BUFFER_TYPE_SYSTEM.
Use unicap_register_callback to tell unicap which function to call on each new frame.
unicap_start_capture activates the video devices. The registered callback gets called when new frames arrive from now on.
The callback gets called in a different thread context: the capture thread context. Here we just wait until the given number of frames was seen by the callback.
unicap_stop_capture deactivates the video capture device.
The callback gets called in the capture thread context. The lowlevel drivers have an internal ring buffer of a size which depends on the video capture device. If a new frame arrives while the callback is still being executed, it is placed into the ring buffer. If the ring buffer is full, the new frames are dropped.