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 package android.media;
18 
19 /**
20  * An immutable object that represents the linear correlation between the media time
21  * and the system time. It contains the media clock rate, together with the media timestamp
22  * of an anchor frame and the system time when that frame was presented or is committed
23  * to be presented.
24  * <p>
25  * The phrase "present" means that audio/video produced on device is detectable by an external
26  * observer off device.
27  * The time is based on the implementation's best effort, using whatever knowledge
28  * is available to the system, but cannot account for any delay unknown to the implementation.
29  * The anchor frame could be any frame, including a just-rendered frame, or even a theoretical
30  * or in-between frame, based on the source of the MediaTimestamp.
31  * When the anchor frame is a just-rendered one, the media time stands for
32  * current position of the playback or recording.
33  *
34  * @see MediaSync#getTimestamp
35  * @see MediaPlayer#getTimestamp
36  */
37 public final class MediaTimestamp
38 {
39     /**
40      * Get the media time of the anchor in microseconds.
41      */
getAnchorMediaTimeUs()42     public long getAnchorMediaTimeUs() {
43         return mediaTimeUs;
44     }
45 
46     /**
47      * Get the {@link java.lang.System#nanoTime system time} corresponding to the media time
48      * in nanoseconds.
49      */
getAnchorSytemNanoTime()50     public long getAnchorSytemNanoTime() {
51         return nanoTime;
52     }
53 
54     /**
55      * Get the rate of the media clock in relation to the system time.
56      * <p>
57      * It is 1.0 if media clock advances in sync with the system clock;
58      * greater than 1.0 if media clock is faster than the system clock;
59      * less than 1.0 if media clock is slower than the system clock.
60      */
getMediaClockRate()61     public float getMediaClockRate() {
62         return clockRate;
63     }
64 
65     /** @hide - accessor shorthand */
66     public final long mediaTimeUs;
67     /** @hide - accessor shorthand */
68     public final long nanoTime;
69     /** @hide - accessor shorthand */
70     public final float clockRate;
71 
72     /** @hide */
MediaTimestamp(long mediaUs, long systemNs, float rate)73     MediaTimestamp(long mediaUs, long systemNs, float rate) {
74         mediaTimeUs = mediaUs;
75         nanoTime = systemNs;
76         clockRate = rate;
77     }
78 
79     /** @hide */
MediaTimestamp()80     MediaTimestamp() {
81         mediaTimeUs = 0;
82         nanoTime = 0;
83         clockRate = 1.0f;
84     }
85 }
86