IsochronousClockModel.h revision e4d7bb418df0fdc4c708c334ba3601f5ed8d89b3 
1/*
2 * Copyright (C) 2016 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 AAUDIO_ISOCHRONOUS_CLOCK_MODEL_H
18#define AAUDIO_ISOCHRONOUS_CLOCK_MODEL_H
19
20#include <stdint.h>
21
22namespace aaudio {
23
24/**
25 * Model an isochronous data stream using occasional timestamps as input.
26 * This can be used to predict the position of the stream at a given time.
27 *
28 * This class is not thread safe and should only be called from one thread.
29 */
30class IsochronousClockModel {
31
32public:
33    IsochronousClockModel();
34    virtual ~IsochronousClockModel();
35
36    void start(int64_t nanoTime);
37    void stop(int64_t nanoTime);
38
39    void processTimestamp(int64_t framePosition, int64_t nanoTime);
40
41    /**
42     * @param sampleRate rate of the stream in frames per second
43     */
44    void setSampleRate(int32_t sampleRate);
45
46    int32_t getSampleRate() const {
47        return mSampleRate;
48    }
49
50    /**
51     * This must be set accurately in order to track the isochronous stream.
52     *
53     * @param framesPerBurst number of frames that stream advance at one time.
54     */
55    void setFramesPerBurst(int32_t framesPerBurst);
56
57    int32_t getFramesPerBurst() const {
58        return mFramesPerBurst;
59    }
60
61    /**
62     * Calculate an estimated time when the stream will be at that position.
63     *
64     * @param framePosition position of the stream in frames
65     * @return time in nanoseconds
66     */
67    int64_t convertPositionToTime(int64_t framePosition) const;
68
69    /**
70     * Calculate an estimated position where the stream will be at the specified time.
71     *
72     * @param nanoTime time of interest
73     * @return position in frames
74     */
75    int64_t convertTimeToPosition(int64_t nanoTime) const;
76
77    /**
78     * @param framesDelta difference in frames
79     * @return duration in nanoseconds
80     */
81    int64_t convertDeltaPositionToTime(int64_t framesDelta) const;
82
83    /**
84     * @param nanosDelta duration in nanoseconds
85     * @return frames that stream will advance in that time
86     */
87    int64_t convertDeltaTimeToPosition(int64_t nanosDelta) const;
88
89private:
90    enum clock_model_state_t {
91        STATE_STOPPED,
92        STATE_STARTING,
93        STATE_SYNCING,
94        STATE_RUNNING
95    };
96
97    int64_t             mMarkerFramePosition;
98    int64_t             mMarkerNanoTime;
99    int32_t             mSampleRate;
100    int32_t             mFramesPerBurst;
101    int32_t             mMaxLatenessInNanos;
102    clock_model_state_t mState;
103
104    void update();
105};
106
107} /* namespace aaudio */
108
109#endif //AAUDIO_ISOCHRONOUS_CLOCK_MODEL_H
110