1 /*
2  * Copyright 2015 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 FLOWGRAPH_RAMP_LINEAR_H
18 #define FLOWGRAPH_RAMP_LINEAR_H
19 
20 #include <atomic>
21 #include <unistd.h>
22 #include <sys/types.h>
23 
24 #include "FlowGraphNode.h"
25 
26 namespace FLOWGRAPH_OUTER_NAMESPACE {
27 namespace flowgraph {
28 
29 /**
30  * When the target is modified then the output will ramp smoothly
31  * between the original and the new target value.
32  * This can be used to smooth out control values and reduce pops.
33  *
34  * The target may be updated while a ramp is in progress, which will trigger
35  * a new ramp from the current value.
36  */
37 class RampLinear : public FlowGraphFilter {
38 public:
39     explicit RampLinear(int32_t channelCount);
40 
41     virtual ~RampLinear() = default;
42 
43     int32_t onProcess(int32_t numFrames) override;
44 
45     /**
46      * This is used for the next ramp.
47      * Calling this does not affect a ramp that is in progress.
48      */
49     void setLengthInFrames(int32_t frames);
50 
getLengthInFrames()51     int32_t getLengthInFrames() const {
52         return mLengthInFrames;
53     }
54 
55     /**
56      * This may be safely called by another thread.
57      * @param target
58      */
59     void setTarget(float target);
60 
getTarget()61     float getTarget() const {
62         return mTarget.load();
63     }
64 
65     /**
66      * Force the nextSegment to start from this level.
67      *
68      * WARNING: this can cause a discontinuity if called while the ramp is being used.
69      * Only call this when setting the initial ramp.
70      *
71      * @param level
72      */
forceCurrent(float level)73     void forceCurrent(float level) {
74         mLevelFrom = level;
75         mLevelTo = level;
76     }
77 
getName()78     const char *getName() override {
79         return "RampLinear";
80     }
81 
82 private:
83 
84     float interpolateCurrent();
85 
86     std::atomic<float>  mTarget;
87 
88     int32_t             mLengthInFrames  = 48000.0f / 100.0f ; // 10 msec at 48000 Hz;
89     int32_t             mRemaining       = 0;
90     float               mScaler          = 0.0f;
91     float               mLevelFrom       = 0.0f;
92     float               mLevelTo         = 0.0f;
93 };
94 
95 } /* namespace flowgraph */
96 } /* namespace FLOWGRAPH_OUTER_NAMESPACE */
97 
98 #endif //FLOWGRAPH_RAMP_LINEAR_H
99