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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      * An unknown media timestamp value
     41      */
     42     public static final MediaTimestamp TIMESTAMP_UNKNOWN = new MediaTimestamp(-1, -1, 0.0f);
     43 
     44     /**
     45      * Get the media time of the anchor in microseconds.
     46      */
     47     public long getAnchorMediaTimeUs() {
     48         return mediaTimeUs;
     49     }
     50 
     51     /**
     52      * Get the {@link java.lang.System#nanoTime system time} corresponding to the media time
     53      * in nanoseconds.
     54      */
     55     public long getAnchorSytemNanoTime() {
     56         return nanoTime;
     57     }
     58 
     59     /**
     60      * Get the rate of the media clock in relation to the system time.
     61      * <p>
     62      * It is 1.0 if media clock advances in sync with the system clock;
     63      * greater than 1.0 if media clock is faster than the system clock;
     64      * less than 1.0 if media clock is slower than the system clock.
     65      */
     66     public float getMediaClockRate() {
     67         return clockRate;
     68     }
     69 
     70     /** @hide - accessor shorthand */
     71     public final long mediaTimeUs;
     72     /** @hide - accessor shorthand */
     73     public final long nanoTime;
     74     /** @hide - accessor shorthand */
     75     public final float clockRate;
     76 
     77     /** @hide */
     78     MediaTimestamp(long mediaUs, long systemNs, float rate) {
     79         mediaTimeUs = mediaUs;
     80         nanoTime = systemNs;
     81         clockRate = rate;
     82     }
     83 
     84     /** @hide */
     85     MediaTimestamp() {
     86         mediaTimeUs = 0;
     87         nanoTime = 0;
     88         clockRate = 1.0f;
     89     }
     90 
     91     @Override
     92     public boolean equals(Object obj) {
     93         if (this == obj) return true;
     94         if (obj == null || getClass() != obj.getClass()) return false;
     95 
     96         final MediaTimestamp that = (MediaTimestamp) obj;
     97         return (this.mediaTimeUs == that.mediaTimeUs)
     98                 && (this.nanoTime == that.nanoTime)
     99                 && (this.clockRate == that.clockRate);
    100     }
    101 
    102     @Override
    103     public String toString() {
    104         return getClass().getName()
    105                 + "{AnchorMediaTimeUs=" + mediaTimeUs
    106                 + " AnchorSystemNanoTime=" + nanoTime
    107                 + " clockRate=" + clockRate
    108                 + "}";
    109     }
    110 }
    111