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