AudioPeakingFilter.cpp revision 2c8e5cab3faa6d360e222b7a6c40a80083d021ac 
1/* //device/include/server/AudioFlinger/AudioPeakingFilter.cpp
2 **
3 ** Copyright 2007, The Android Open Source Project
4 **
5 ** Licensed under the Apache License, Version 2.0 (the "License");
6 ** you may not use this file except in compliance with the License.
7 ** You may obtain a copy of the License at
8 **
9 **     http://www.apache.org/licenses/LICENSE-2.0
10 **
11 ** Unless required by applicable law or agreed to in writing, software
12 ** distributed under the License is distributed on an "AS IS" BASIS,
13 ** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14 ** See the License for the specific language governing permissions and
15 ** limitations under the License.
16 */
17
18#include "AudioPeakingFilter.h"
19#include "AudioCommon.h"
20#include "EffectsMath.h"
21
22#include <new>
23#include <assert.h>
24
25#define LIKELY( exp )       (__builtin_expect( (exp) != 0, true  ))
26#define UNLIKELY( exp )     (__builtin_expect( (exp) != 0, false ))
27
28namespace android {
29// Format of the coefficient table:
30// kCoefTable[freq][gain][bw][coef]
31// freq - peak frequency, in octaves below Nyquist,from -9 to -1.
32// gain - gain, in millibel, starting at -9600, jumps of 1024, to 4736 millibel.
33// bw   - bandwidth, starting at 1 cent, jumps of 1024, to 3073 cents.
34// coef - 0: b0
35//        1: b1
36//        2: b2
37//        3: -a1
38//        4: -a2
39static const size_t kInDims[3] = {9, 15, 4};
40static const audio_coef_t kCoefTable[9*15*4*5] = {
41#include "AudioPeakingFilterCoef.inl"
42};
43
44AudioCoefInterpolator AudioPeakingFilter::mCoefInterp(3, kInDims, 5, (const audio_coef_t*) kCoefTable);
45
46AudioPeakingFilter::AudioPeakingFilter(int nChannels, int sampleRate)
47        : mBiquad(nChannels, sampleRate) {
48    configure(nChannels, sampleRate);
49    reset();
50}
51
52void AudioPeakingFilter::configure(int nChannels, int sampleRate) {
53    mNiquistFreq = sampleRate * 500;
54    mFrequencyFactor = ((1ull) << 42) / mNiquistFreq;
55    mBiquad.configure(nChannels, sampleRate);
56    setFrequency(mNominalFrequency);
57    commit(true);
58}
59
60void AudioPeakingFilter::reset() {
61    setGain(0);
62    setFrequency(0);
63    setBandwidth(2400);
64    commit(true);
65}
66
67void AudioPeakingFilter::setFrequency(uint32_t millihertz) {
68    mNominalFrequency = millihertz;
69    if (UNLIKELY(millihertz > mNiquistFreq / 2)) {
70        millihertz = mNiquistFreq / 2;
71    }
72    uint32_t normFreq = static_cast<uint32_t>(
73            (static_cast<uint64_t>(millihertz) * mFrequencyFactor) >> 10);
74    if (LIKELY(normFreq > (1 << 23))) {
75        mFrequency = (Effects_log2(normFreq) - ((32-9) << 15)) << (FREQ_PRECISION_BITS - 15);
76    } else {
77        mFrequency = 0;
78    }
79}
80
81void AudioPeakingFilter::setGain(int32_t millibel) {
82    mGain = millibel + 9600;
83}
84
85void AudioPeakingFilter::setBandwidth(uint32_t cents) {
86    mBandwidth = cents - 1;
87}
88
89void AudioPeakingFilter::commit(bool immediate) {
90    audio_coef_t coefs[5];
91    int intCoord[3] = {
92        mFrequency >> FREQ_PRECISION_BITS,
93        mGain >> GAIN_PRECISION_BITS,
94        mBandwidth >> BANDWIDTH_PRECISION_BITS
95    };
96    uint32_t fracCoord[3] = {
97        mFrequency << (32 - FREQ_PRECISION_BITS),
98        static_cast<uint32_t>(mGain) << (32 - GAIN_PRECISION_BITS),
99        mBandwidth << (32 - BANDWIDTH_PRECISION_BITS)
100    };
101    mCoefInterp.getCoef(intCoord, fracCoord, coefs);
102    mBiquad.setCoefs(coefs, immediate);
103}
104
105void AudioPeakingFilter::getBandRange(uint32_t & low, uint32_t & high) const {
106    // Half bandwidth, in octaves, 15-bit precision
107    int32_t halfBW = (((mBandwidth + 1) / 2) << 15) / 1200;
108
109    low = static_cast<uint32_t>((static_cast<uint64_t>(mNominalFrequency) * Effects_exp2(-halfBW + (16 << 15))) >> 16);
110    if (UNLIKELY(halfBW >= (16 << 15))) {
111        high = mNiquistFreq;
112    } else {
113        high = static_cast<uint32_t>((static_cast<uint64_t>(mNominalFrequency) * Effects_exp2(halfBW + (16 << 15))) >> 16);
114        if (UNLIKELY(high > mNiquistFreq)) {
115            high = mNiquistFreq;
116        }
117    }
118}
119
120}
121
122