66 lines
2.3 KiB
Python
66 lines
2.3 KiB
Python
# Copyright 2014 The Android Open Source Project
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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import its.image
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import its.caps
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import its.device
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import its.objects
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import os.path
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import pylab
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import matplotlib
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import matplotlib.pyplot
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def main():
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"""Measure jitter in camera timestamps.
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"""
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NAME = os.path.basename(__file__).split(".")[0]
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# Pass/fail thresholds
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MIN_AVG_FRAME_DELTA = 30 # at least 30ms delta between frames
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MAX_VAR_FRAME_DELTA = 0.01 # variance of frame deltas
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MAX_FRAME_DELTA_JITTER = 0.3 # max ms gap from the average frame delta
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with its.device.ItsSession() as cam:
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props = cam.get_camera_properties()
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its.caps.skip_unless(its.caps.manual_sensor(props) and
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its.caps.sensor_fusion(props))
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req, fmt = its.objects.get_fastest_manual_capture_settings(props)
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caps = cam.do_capture([req]*50, [fmt])
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# Print out the millisecond delta between the start of each exposure
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tstamps = [c['metadata']['android.sensor.timestamp'] for c in caps]
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deltas = [tstamps[i]-tstamps[i-1] for i in range(1,len(tstamps))]
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deltas_ms = [d/1000000.0 for d in deltas]
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avg = sum(deltas_ms) / len(deltas_ms)
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var = sum([d*d for d in deltas_ms]) / len(deltas_ms) - avg * avg
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range0 = min(deltas_ms) - avg
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range1 = max(deltas_ms) - avg
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print "Average:", avg
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print "Variance:", var
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print "Jitter range:", range0, "to", range1
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# Draw a plot.
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pylab.plot(range(len(deltas_ms)), deltas_ms)
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matplotlib.pyplot.savefig("%s_deltas.png" % (NAME))
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# Test for pass/fail.
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assert(avg > MIN_AVG_FRAME_DELTA)
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assert(var < MAX_VAR_FRAME_DELTA)
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assert(abs(range0) < MAX_FRAME_DELTA_JITTER)
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assert(abs(range1) < MAX_FRAME_DELTA_JITTER)
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if __name__ == '__main__':
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main()
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