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      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      */
     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      */
     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      */
     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 */
     73     MediaTimestamp(long mediaUs, long systemNs, float rate) {
     74         mediaTimeUs = mediaUs;
     75         nanoTime = systemNs;
     76         clockRate = rate;
     77     }
     78 
     79     /** @hide */
     80     MediaTimestamp() {
     81         mediaTimeUs = 0;
     82         nanoTime = 0;
     83         clockRate = 1.0f;
     84     }
     85 }
     86