1 /*
2  * Copyright (C) 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 package com.android.tv.tuner.exoplayer.audio;
18 
19 import android.os.SystemClock;
20 import com.android.tv.common.SoftPreconditions;
21 
22 /**
23  * Copy of {@link com.google.android.exoplayer.MediaClock}.
24  *
25  * <p>A simple clock for tracking the progression of media time. The clock can be started, stopped
26  * and its time can be set and retrieved. When started, this clock is based on {@link
27  * SystemClock#elapsedRealtime()}.
28  */
29 /* package */ class AudioClock {
30     private boolean mStarted;
31 
32     /** The media time when the clock was last set or stopped. */
33     private long mPositionUs;
34 
35     /**
36      * The difference between {@link SystemClock#elapsedRealtime()} and {@link #mPositionUs} when
37      * the clock was last set or mStarted.
38      */
39     private long mDeltaUs;
40 
41     private float mPlaybackSpeed = 1.0f;
42     private long mDeltaUpdatedTimeUs;
43 
44     /** Starts the clock. Does nothing if the clock is already started. */
start()45     public void start() {
46         if (!mStarted) {
47             mStarted = true;
48             mDeltaUs = elapsedRealtimeMinus(mPositionUs);
49             mDeltaUpdatedTimeUs = SystemClock.elapsedRealtime() * 1000;
50         }
51     }
52 
53     /** Stops the clock. Does nothing if the clock is already stopped. */
stop()54     public void stop() {
55         if (mStarted) {
56             mPositionUs = elapsedRealtimeMinus(mDeltaUs);
57             mStarted = false;
58         }
59     }
60 
61     /** @param timeUs The position to set in microseconds. */
setPositionUs(long timeUs)62     public void setPositionUs(long timeUs) {
63         this.mPositionUs = timeUs;
64         mDeltaUs = elapsedRealtimeMinus(timeUs);
65         mDeltaUpdatedTimeUs = SystemClock.elapsedRealtime() * 1000;
66     }
67 
68     /** @return The current position in microseconds. */
getPositionUs()69     public long getPositionUs() {
70         if (!mStarted) {
71             return mPositionUs;
72         }
73         if (mPlaybackSpeed != 1.0f) {
74             long elapsedTimeFromPlaybackSpeedChanged =
75                     SystemClock.elapsedRealtime() * 1000 - mDeltaUpdatedTimeUs;
76             return elapsedRealtimeMinus(mDeltaUs)
77                     + (long) ((mPlaybackSpeed - 1.0f) * elapsedTimeFromPlaybackSpeedChanged);
78         } else {
79             return elapsedRealtimeMinus(mDeltaUs);
80         }
81     }
82 
83     /** Sets playback speed. {@code speed} should be positive. */
setPlaybackSpeed(float speed)84     public void setPlaybackSpeed(float speed) {
85         SoftPreconditions.checkState(speed > 0);
86         mDeltaUs = elapsedRealtimeMinus(getPositionUs());
87         mDeltaUpdatedTimeUs = SystemClock.elapsedRealtime() * 1000;
88         mPlaybackSpeed = speed;
89     }
90 
elapsedRealtimeMinus(long toSubtractUs)91     private long elapsedRealtimeMinus(long toSubtractUs) {
92         return SystemClock.elapsedRealtime() * 1000 - toSubtractUs;
93     }
94 }
95