AudioResampler.h revision e53b9ead781c36e96d6b6f012ddffc93a3d80f0d 
1/*
2 * Copyright (C) 2007 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of 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,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef ANDROID_AUDIO_RESAMPLER_H
18#define ANDROID_AUDIO_RESAMPLER_H
19
20#include <stdint.h>
21#include <sys/types.h>
22
23#include "AudioBufferProvider.h"
24
25namespace android {
26// ----------------------------------------------------------------------------
27
28class AudioResampler {
29public:
30    // Determines quality of SRC.
31    //  LOW_QUALITY: linear interpolator (1st order)
32    //  MED_QUALITY: cubic interpolator (3rd order)
33    //  HIGH_QUALITY: fixed multi-tap FIR (e.g. 48KHz->44.1KHz)
34    // NOTE: high quality SRC will only be supported for
35    // certain fixed rate conversions. Sample rate cannot be
36    // changed dynamically.
37    enum src_quality {
38        DEFAULT=0,
39        LOW_QUALITY=1,
40        MED_QUALITY=2,
41        HIGH_QUALITY=3
42    };
43
44    static AudioResampler* create(int bitDepth, int inChannelCount,
45            int32_t sampleRate, int quality=DEFAULT);
46
47    virtual ~AudioResampler();
48
49    virtual void init() = 0;
50    virtual void setSampleRate(int32_t inSampleRate);
51    virtual void setVolume(int16_t left, int16_t right);
52    virtual void setLocalTimeFreq(uint64_t freq);
53
54    // set the PTS of the next buffer output by the resampler
55    virtual void setPTS(int64_t pts);
56
57    virtual void resample(int32_t* out, size_t outFrameCount,
58            AudioBufferProvider* provider) = 0;
59
60    virtual void reset();
61    virtual size_t getUnreleasedFrames() const { return mInputIndex; }
62
63protected:
64    // number of bits for phase fraction - 30 bits allows nearly 2x downsampling
65    static const int kNumPhaseBits = 30;
66
67    // phase mask for fraction
68    static const uint32_t kPhaseMask = (1LU<<kNumPhaseBits)-1;
69
70    // multiplier to calculate fixed point phase increment
71    static const double kPhaseMultiplier = 1L << kNumPhaseBits;
72
73    AudioResampler(int bitDepth, int inChannelCount, int32_t sampleRate);
74
75    // prevent copying
76    AudioResampler(const AudioResampler&);
77    AudioResampler& operator=(const AudioResampler&);
78
79    int64_t calculateOutputPTS(int outputFrameIndex);
80
81    const int32_t mBitDepth;
82    const int32_t mChannelCount;
83    const int32_t mSampleRate;
84    int32_t mInSampleRate;
85    AudioBufferProvider::Buffer mBuffer;
86    union {
87        int16_t mVolume[2];
88        uint32_t mVolumeRL;
89    };
90    int16_t mTargetVolume[2];
91    size_t mInputIndex;
92    int32_t mPhaseIncrement;
93    uint32_t mPhaseFraction;
94    uint64_t mLocalTimeFreq;
95    int64_t mPTS;
96};
97
98// ----------------------------------------------------------------------------
99}
100; // namespace android
101
102#endif // ANDROID_AUDIO_RESAMPLER_H
103