| /* |
| * Copyright 2017 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| #ifndef AAUDIO_LINEAR_RAMP_H |
| #define AAUDIO_LINEAR_RAMP_H |
| |
| #include <atomic> |
| #include <stdint.h> |
| |
| /** |
| * Generate segments along a linear ramp. |
| * The ramp target can be updated from another thread. |
| * When the target is updated, a new ramp is started from the current position. |
| * |
| * The first ramp starts at 0.0. |
| * |
| */ |
| class LinearRamp { |
| public: |
| LinearRamp() { |
| mTarget.store(1.0f); |
| } |
| |
| void setLengthInFrames(int32_t frames) { |
| mLengthInFrames = frames; |
| } |
| |
| int32_t getLengthInFrames() { |
| return mLengthInFrames; |
| } |
| |
| /** |
| * This may be called by another thread. |
| * @param target |
| */ |
| void setTarget(float target) { |
| mTarget.store(target); |
| } |
| |
| float getTarget() { |
| return mTarget.load(); |
| } |
| |
| /** |
| * Force the nextSegment to start from this level. |
| * |
| * WARNING: this can cause a discontinuity if called while the ramp is being used. |
| * Only call this when setting the initial ramp. |
| * |
| * @param level |
| */ |
| void forceCurrent(float level) { |
| mLevelFrom = level; |
| mLevelTo = level; // forces a ramp if it does not match target |
| } |
| |
| float getCurrent() { |
| return mLevelFrom; |
| } |
| |
| /** |
| * Get levels for next ramp segment. |
| * |
| * @param frames number of frames in the segment |
| * @param levelFrom pointer to starting amplitude |
| * @param levelTo pointer to ending amplitude |
| * @return true if ramp is still moving towards the target |
| */ |
| bool nextSegment(int32_t frames, float *levelFrom, float *levelTo); |
| |
| private: |
| |
| bool isRamping(); |
| |
| std::atomic<float> mTarget; |
| |
| int32_t mLengthInFrames = 48000 / 50; // 20 msec at 48000 Hz |
| int32_t mRemaining = 0; |
| float mLevelFrom = 0.0f; |
| float mLevelTo = 0.0f; |
| }; |
| |
| |
| #endif //AAUDIO_LINEAR_RAMP_H |