1 # Copyright 2014 The Android Open Source Project 2 # 3 # Licensed under the Apache License, Version 2.0 (the "License"); 4 # you may not use this file except in compliance with the License. 5 # You may obtain a copy of the License at 6 # 7 # http://www.apache.org/licenses/LICENSE-2.0 8 # 9 # Unless required by applicable law or agreed to in writing, software 10 # distributed under the License is distributed on an "AS IS" BASIS, 11 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 # See the License for the specific language governing permissions and 13 # limitations under the License. 14 15 import os.path 16 17 import its.caps 18 import its.device 19 import its.image 20 import its.objects 21 22 import matplotlib 23 from matplotlib import pylab 24 25 # PASS/FAIL thresholds 26 MIN_AVG_FRAME_DELTA = 30 # at least 30ms delta between frames 27 MAX_VAR_FRAME_DELTA = 0.01 # variance of frame deltas 28 MAX_FRAME_DELTA_JITTER = 0.3 # max ms gap from the average frame delta 29 30 NAME = os.path.basename(__file__).split('.')[0] 31 32 33 def main(): 34 """Measure jitter in camera timestamps.""" 35 36 with its.device.ItsSession() as cam: 37 props = cam.get_camera_properties() 38 its.caps.skip_unless(its.caps.manual_sensor(props) and 39 its.caps.sensor_fusion(props)) 40 41 req, fmt = its.objects.get_fastest_manual_capture_settings(props) 42 caps = cam.do_capture([req]*50, [fmt]) 43 44 # Print out the millisecond delta between the start of each exposure 45 tstamps = [c['metadata']['android.sensor.timestamp'] for c in caps] 46 deltas = [tstamps[i]-tstamps[i-1] for i in range(1, len(tstamps))] 47 deltas_ms = [d/1000000.0 for d in deltas] 48 avg = sum(deltas_ms) / len(deltas_ms) 49 var = sum([d*d for d in deltas_ms]) / len(deltas_ms) - avg * avg 50 range0 = min(deltas_ms) - avg 51 range1 = max(deltas_ms) - avg 52 print 'Average:', avg 53 print 'Variance:', var 54 print 'Jitter range:', range0, 'to', range1 55 56 # Draw a plot. 57 pylab.plot(range(len(deltas_ms)), deltas_ms) 58 pylab.title(NAME) 59 pylab.xlabel('frame number') 60 pylab.ylabel('jitter (ms)') 61 matplotlib.pyplot.savefig('%s_deltas.png' % (NAME)) 62 63 # Test for pass/fail. 64 emsg = 'avg: %.4fms, TOL: %.fms' % (avg, MIN_AVG_FRAME_DELTA) 65 assert avg > MIN_AVG_FRAME_DELTA, emsg 66 emsg = 'var: %.4fms, TOL: %.2fms' % (var, MAX_VAR_FRAME_DELTA) 67 assert var < MAX_VAR_FRAME_DELTA, emsg 68 emsg = 'range0: %.4fms, range1: %.4fms, TOL: %.2fms' % ( 69 range0, range1, MAX_FRAME_DELTA_JITTER) 70 assert abs(range0) < MAX_FRAME_DELTA_JITTER, emsg 71 assert abs(range1) < MAX_FRAME_DELTA_JITTER, emsg 72 73 if __name__ == '__main__': 74 main() 75 76
