API for stream output

[adamkglaser]

@aliddell @nclack It would be useful to be able to track dropped frames via the eGrabber SDK, and perhaps more generally the entire video stream. Other camera SDKs may not offer functions for this, but with eGrabber /GenICam it is relatively straightforward. A code snippet in Python for how we are doing this now below, would be nice if we could do the same in ACQUIRE?

def signal_acquisition_state(self):
"""return a dict with the state of the acquisition buffers"""
# Detailed description of constants here:
# https://documentation.euresys.com/Products/Coaxlink/Coaxlink/en-us/Content/IOdoc/egrabber-reference/
# namespace_gen_t_l.html#a6b498d9a4c08dea2c44566722699706e
state = {}
state['Frame Index'] = self.grabber.stream.get_info(STREAM_INFO_NUM_DELIVERED, INFO_DATATYPE_SIZET)
state['Input Buffer Size'] = self.grabber.stream.get_info(STREAM_INFO_NUM_QUEUED,
                                                     INFO_DATATYPE_SIZET)
state['Output Buffer Size'] = self.grabber.stream.get_info(STREAM_INFO_NUM_AWAIT_DELIVERY,
                                                        INFO_DATATYPE_SIZET)
# number of underrun, i.e. dropped frames
state['Dropped Frames'] = self.grabber.stream.get_info(STREAM_INFO_NUM_UNDERRUN,
                                                     INFO_DATATYPE_SIZET)
state['Data Rate [MB/s]'] = self.grabber.stream.get('StatisticsDataRate')
state['Frame Rate [fps]'] = self.grabber.stream.get('StatisticsFrameRate')
self.log.info(f"id: {self.id}, "
             f"frame: {state['Frame Index']}, "
             f"input: {state['Input Buffer Size']}, "
             f"output: {state['Output Buffer Size']}, "
             f"dropped: {state['Dropped Frames']}, "
             f"data rate: {state['Data Rate [MB/s]']:.2f} [MB/s], "
             f"frame rate: {state['Frame Rate [fps]']:.2f} [fps].")
return state