1 /* 2 * Copyright (C) 2010 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); you may not 5 * use this file except in compliance with the License. You may obtain a copy of 6 * the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the 13 * License for the specific language governing permissions and limitations under 14 * the License. 15 */ 16 17 #ifndef COMPARE_SPECTRA_H 18 #define COMPARE_SPECTRA_H 19 20 /* Compare the average magnitude spectra of the signals in pcm and 21 refPcm, which are of length numSamples and nRefSamples, 22 respectively; both sampled at sample_rate. The maximum deviation 23 between average spectra, expressed in dB, is returned in 24 maxDeviation, and the rms of all dB variations is returned in 25 rmsDeviation. Note that a lower limit is set on the frequencies that 26 are compared so as to ignore irrelevant DC and rumble components. If 27 the measurement fails for some reason, return 0; else return 1, for 28 success. Causes for failure include the amplitude of one or both of 29 the signals being too low, or the duration of the signals being too 30 short. 31 32 Note that the expected signal collection scenario is that the phone 33 would be stimulated with a broadband signal as in a recognition 34 attempt, so that there will be some "silence" regions at the start and 35 end of the pcm signals. The preferred stimulus would be pink noise, 36 but any broadband signal should work. */ 37 38 int compareSpectra(short* pcm, int numSamples, short* refPcm, 39 int nRefSamples, float sampleRate, 40 float* maxDeviation, float* rmsDeviation); 41 42 #endif // COMPARE_SPECTRA_H 43