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
15import os.path
16
17import its.caps
18import its.device
19import its.image
20import its.objects
21
22import matplotlib
23from matplotlib import pylab
24
25# PASS/FAIL thresholds
26TEST_FPS = 30
27MIN_AVG_FRAME_DELTA = 30  # at least 30ms delta between frames
28MAX_VAR_FRAME_DELTA = 0.01  # variance of frame deltas
29MAX_FRAME_DELTA_JITTER = 0.3  # max ms gap from the average frame delta
30
31NAME = os.path.basename(__file__).split('.')[0]
32
33
34def main():
35    """Measure jitter in camera timestamps."""
36
37    with its.device.ItsSession() as cam:
38        props = cam.get_camera_properties()
39        its.caps.skip_unless(its.caps.manual_sensor(props) and
40                             its.caps.sensor_fusion(props))
41
42        req, fmt = its.objects.get_fastest_manual_capture_settings(props)
43        req["android.control.aeTargetFpsRange"] = [TEST_FPS, TEST_FPS]
44        caps = cam.do_capture([req]*50, [fmt])
45
46        # Print out the millisecond delta between the start of each exposure
47        tstamps = [c['metadata']['android.sensor.timestamp'] for c in caps]
48        deltas = [tstamps[i]-tstamps[i-1] for i in range(1, len(tstamps))]
49        deltas_ms = [d/1000000.0 for d in deltas]
50        avg = sum(deltas_ms) / len(deltas_ms)
51        var = sum([d*d for d in deltas_ms]) / len(deltas_ms) - avg * avg
52        range0 = min(deltas_ms) - avg
53        range1 = max(deltas_ms) - avg
54        print 'Average:', avg
55        print 'Variance:', var
56        print 'Jitter range:', range0, 'to', range1
57
58        # Draw a plot.
59        pylab.plot(range(len(deltas_ms)), deltas_ms)
60        pylab.title(NAME)
61        pylab.xlabel('frame number')
62        pylab.ylabel('jitter (ms)')
63        matplotlib.pyplot.savefig('%s_deltas.png' % (NAME))
64
65        # Test for pass/fail.
66        emsg = 'avg: %.4fms, TOL: %.fms' % (avg, MIN_AVG_FRAME_DELTA)
67        assert avg > MIN_AVG_FRAME_DELTA, emsg
68        emsg = 'var: %.4fms, TOL: %.2fms' % (var, MAX_VAR_FRAME_DELTA)
69        assert var < MAX_VAR_FRAME_DELTA, emsg
70        emsg = 'range0: %.4fms, range1: %.4fms, TOL: %.2fms' % (
71                range0, range1, MAX_FRAME_DELTA_JITTER)
72        assert abs(range0) < MAX_FRAME_DELTA_JITTER, emsg
73        assert abs(range1) < MAX_FRAME_DELTA_JITTER, emsg
74
75if __name__ == '__main__':
76    main()
77
78