1 /*
2 * Copyright (C) 2014 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_PUBLIC_H
18 #define ANDROID_AUDIO_RESAMPLER_PUBLIC_H
19
20 #include <stdint.h>
21 #include <math.h>
22 #include <system/audio.h>
23
24 namespace android {
25
26 // AUDIO_RESAMPLER_DOWN_RATIO_MAX is the maximum ratio between the original
27 // audio sample rate and the target rate when downsampling,
28 // as permitted in the audio framework, e.g. AudioTrack and AudioFlinger.
29 // In practice, it is not recommended to downsample more than 6:1
30 // for best audio quality, even though the audio framework permits a larger
31 // downsampling ratio.
32 // TODO: replace with an API
33 #define AUDIO_RESAMPLER_DOWN_RATIO_MAX 256
34
35 // AUDIO_RESAMPLER_UP_RATIO_MAX is the maximum suggested ratio between the original
36 // audio sample rate and the target rate when upsampling. It is loosely enforced by
37 // the system. One issue with large upsampling ratios is the approximation by
38 // an int32_t of the phase increments, making the resulting sample rate inexact.
39 #define AUDIO_RESAMPLER_UP_RATIO_MAX 65536
40
41 //Determines the current algorithm used for stretching
42 using AudioTimestretchStretchMode = ::audio_timestretch_stretch_mode_t;
43
44 //Determines behavior of Timestretch if current algorithm can't perform
45 //with current parameters.
46 using AudioTimestretchFallbackMode = ::audio_timestretch_fallback_mode_t;
47
48 using AudioPlaybackRate = ::audio_playback_rate_t;
49
50 static const AudioPlaybackRate AUDIO_PLAYBACK_RATE_DEFAULT = ::AUDIO_PLAYBACK_RATE_INITIALIZER;
51
isAudioPlaybackRateEqual(const AudioPlaybackRate & pr1,const AudioPlaybackRate & pr2)52 static inline bool isAudioPlaybackRateEqual(const AudioPlaybackRate &pr1,
53 const AudioPlaybackRate &pr2) {
54 return fabs(pr1.mSpeed - pr2.mSpeed) < AUDIO_TIMESTRETCH_SPEED_MIN_DELTA &&
55 fabs(pr1.mPitch - pr2.mPitch) < AUDIO_TIMESTRETCH_PITCH_MIN_DELTA &&
56 pr1.mStretchMode == pr2.mStretchMode &&
57 pr1.mFallbackMode == pr2.mFallbackMode;
58 }
59
isAudioPlaybackRateValid(const AudioPlaybackRate & playbackRate)60 static inline bool isAudioPlaybackRateValid(const AudioPlaybackRate &playbackRate) {
61 if (playbackRate.mFallbackMode == AUDIO_TIMESTRETCH_FALLBACK_FAIL &&
62 (playbackRate.mStretchMode == AUDIO_TIMESTRETCH_STRETCH_VOICE ||
63 playbackRate.mStretchMode == AUDIO_TIMESTRETCH_STRETCH_DEFAULT)) {
64 //test sonic specific constraints
65 return playbackRate.mSpeed >= TIMESTRETCH_SONIC_SPEED_MIN &&
66 playbackRate.mSpeed <= TIMESTRETCH_SONIC_SPEED_MAX &&
67 playbackRate.mPitch >= AUDIO_TIMESTRETCH_PITCH_MIN &&
68 playbackRate.mPitch <= AUDIO_TIMESTRETCH_PITCH_MAX;
69 } else {
70 return playbackRate.mSpeed >= AUDIO_TIMESTRETCH_SPEED_MIN &&
71 playbackRate.mSpeed <= AUDIO_TIMESTRETCH_SPEED_MAX &&
72 playbackRate.mPitch >= AUDIO_TIMESTRETCH_PITCH_MIN &&
73 playbackRate.mPitch <= AUDIO_TIMESTRETCH_PITCH_MAX;
74 }
75 }
76
77 // TODO: Consider putting these inlines into a class scope
78
79 // Returns the source frames needed to resample to destination frames. This is not a precise
80 // value and depends on the resampler (and possibly how it handles rounding internally).
81 // Nevertheless, this should be an upper bound on the requirements of the resampler.
82 // If srcSampleRate and dstSampleRate are equal, then it returns destination frames, which
83 // may not be true if the resampler is asynchronous.
sourceFramesNeeded(uint32_t srcSampleRate,size_t dstFramesRequired,uint32_t dstSampleRate)84 static inline size_t sourceFramesNeeded(
85 uint32_t srcSampleRate, size_t dstFramesRequired, uint32_t dstSampleRate) {
86 // +1 for rounding - always do this even if matched ratio (resampler may use phases not ratio)
87 // +1 for additional sample needed for interpolation
88 return srcSampleRate == dstSampleRate ? dstFramesRequired :
89 size_t((uint64_t)dstFramesRequired * srcSampleRate / dstSampleRate + 1 + 1);
90 }
91
92 // An upper bound for the number of destination frames possible from srcFrames
93 // after sample rate conversion. This may be used for buffer sizing.
destinationFramesPossible(size_t srcFrames,uint32_t srcSampleRate,uint32_t dstSampleRate)94 static inline size_t destinationFramesPossible(size_t srcFrames, uint32_t srcSampleRate,
95 uint32_t dstSampleRate) {
96 if (srcSampleRate == dstSampleRate) {
97 return srcFrames;
98 }
99 uint64_t dstFrames = (uint64_t)srcFrames * dstSampleRate / srcSampleRate;
100 return dstFrames > 2 ? dstFrames - 2 : 0;
101 }
102
sourceFramesNeededWithTimestretch(uint32_t srcSampleRate,size_t dstFramesRequired,uint32_t dstSampleRate,float speed)103 static inline size_t sourceFramesNeededWithTimestretch(
104 uint32_t srcSampleRate, size_t dstFramesRequired, uint32_t dstSampleRate,
105 float speed) {
106 // required is the number of input frames the resampler needs
107 size_t required = sourceFramesNeeded(srcSampleRate, dstFramesRequired, dstSampleRate);
108 // to deliver this, the time stretcher requires:
109 return required * (double)speed + 1 + 1; // accounting for rounding dependencies
110 }
111
112 // Identifies sample rates that we associate with music
113 // and thus eligible for better resampling and fast capture.
114 // This is somewhat less than 44100 to allow for pitch correction
115 // involving resampling as well as asynchronous resampling.
116 #define AUDIO_PROCESSING_MUSIC_RATE 40000
117
isMusicRate(uint32_t sampleRate)118 static inline bool isMusicRate(uint32_t sampleRate) {
119 return sampleRate >= AUDIO_PROCESSING_MUSIC_RATE;
120 }
121
122 } // namespace android
123
124 // ---------------------------------------------------------------------------
125
126 #endif // ANDROID_AUDIO_RESAMPLER_PUBLIC_H
127