content: /*
   * Copyright (C) 2020 The Android Open Source Project
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *      http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.google.android.exoplayer2.video;
  
  import static com.google.android.exoplayer2.video.FixedFrameRateEstimator.CONSECUTIVE_MATCHING_FRAME_DURATIONS_FOR_SYNC;
  import static com.google.android.exoplayer2.video.FixedFrameRateEstimator.MAX_MATCHING_FRAME_DIFFERENCE_NS;
  import static com.google.common.truth.Truth.assertThat;
  
  import androidx.test.ext.junit.runners.AndroidJUnit4;
  import com.google.android.exoplayer2.C;
  import org.junit.Test;
  import org.junit.runner.RunWith;
  
  /** Unit test for {@link FixedFrameRateEstimator}. */
  @RunWith(AndroidJUnit4.class)
  public final class FixedFrameRateEstimatorTest {
  
    @Test
    public void fixedFrameRate_withSingleOutlier_syncsAndResyncs() {
      long frameDurationNs = 33_333_333;
      FixedFrameRateEstimator estimator = new FixedFrameRateEstimator();
  
      // Initial frame.
      long framePresentationTimestampNs = 0;
      estimator.onNextFrame(framePresentationTimestampNs);
  
      assertThat(estimator.isSynced()).isFalse();
      assertThat(estimator.getFrameDurationNs()).isEqualTo(C.TIME_UNSET);
  
      // Frames with consistent durations, working toward establishing sync.
      for (int i = 0; i < CONSECUTIVE_MATCHING_FRAME_DURATIONS_FOR_SYNC - 1; i++) {
        framePresentationTimestampNs += frameDurationNs;
        estimator.onNextFrame(framePresentationTimestampNs);
  
        assertThat(estimator.isSynced()).isFalse();
        assertThat(estimator.getFrameDurationNs()).isEqualTo(C.TIME_UNSET);
      }
  
      // This frame should establish sync.
      framePresentationTimestampNs += frameDurationNs;
      estimator.onNextFrame(framePresentationTimestampNs);
  
      assertThat(estimator.isSynced()).isTrue();
      assertThat(estimator.getFrameDurationNs()).isEqualTo(frameDurationNs);
  
      framePresentationTimestampNs += frameDurationNs;
      // Make the frame duration just shorter enough to lose sync.
      framePresentationTimestampNs -= MAX_MATCHING_FRAME_DIFFERENCE_NS + 1;
      estimator.onNextFrame(framePresentationTimestampNs);
  
      assertThat(estimator.isSynced()).isFalse();
      assertThat(estimator.getFrameDurationNs()).isEqualTo(C.TIME_UNSET);
  
      // Frames with consistent durations, working toward re-establishing sync.
      for (int i = 0; i < CONSECUTIVE_MATCHING_FRAME_DURATIONS_FOR_SYNC - 1; i++) {
        framePresentationTimestampNs += frameDurationNs;
        estimator.onNextFrame(framePresentationTimestampNs);
  
        assertThat(estimator.isSynced()).isFalse();
        assertThat(estimator.getFrameDurationNs()).isEqualTo(C.TIME_UNSET);
      }
  
      // This frame should re-establish sync.
      framePresentationTimestampNs += frameDurationNs;
      estimator.onNextFrame(framePresentationTimestampNs);
  
      assertThat(estimator.isSynced()).isTrue();
      assertThat(estimator.getFrameDurationNs()).isEqualTo(frameDurationNs);
    }
  
    @Test
    public void fixedFrameRate_withOutlierFirstFrameDuration_syncs() {
      long frameDurationNs = 33_333_333;
      FixedFrameRateEstimator estimator = new FixedFrameRateEstimator();
  
      // Initial frame with double duration.
      long framePresentationTimestampNs = 0;
      estimator.onNextFrame(framePresentationTimestampNs);
  
      framePresentationTimestampNs += frameDurationNs * 2;
      estimator.onNextFrame(framePresentationTimestampNs);
  
      assertThat(estimator.isSynced()).isFalse();
      assertThat(estimator.getFrameDurationNs()).isEqualTo(C.TIME_UNSET);
  
      // Frames with consistent durations, working toward establishing sync.
      for (int i = 0; i < CONSECUTIVE_MATCHING_FRAME_DURATIONS_FOR_SYNC - 1; i++) {
        framePresentationTimestampNs += frameDurationNs;
        estimator.onNextFrame(framePresentationTimestampNs);
  
        assertThat(estimator.isSynced()).isFalse();
        assertThat(estimator.getFrameDurationNs()).isEqualTo(C.TIME_UNSET);
      }
  
      // This frame should establish sync.
      framePresentationTimestampNs += frameDurationNs;
      estimator.onNextFrame(framePresentationTimestampNs);
    }
  
    @Test
    public void newFixedFrameRate_resyncs() {
      long frameDurationNs = 33_333_333;
      FixedFrameRateEstimator estimator = new FixedFrameRateEstimator();
  
      long framePresentationTimestampNs = 0;
      estimator.onNextFrame(framePresentationTimestampNs);
      for (int i = 0; i < CONSECUTIVE_MATCHING_FRAME_DURATIONS_FOR_SYNC; i++) {
        framePresentationTimestampNs += frameDurationNs;
        estimator.onNextFrame(framePresentationTimestampNs);
      }
  
      assertThat(estimator.isSynced()).isTrue();
      assertThat(estimator.getFrameDurationNs()).isEqualTo(frameDurationNs);
  
      // Frames durations are halved from this point.
      long halfFrameRateDuration = frameDurationNs / 2;
  
      // Frames with consistent durations, working toward establishing new sync.
      for (int i = 0; i < CONSECUTIVE_MATCHING_FRAME_DURATIONS_FOR_SYNC - 1; i++) {
        framePresentationTimestampNs += halfFrameRateDuration;
        estimator.onNextFrame(framePresentationTimestampNs);
  
        assertThat(estimator.isSynced()).isFalse();
        assertThat(estimator.getFrameDurationNs()).isEqualTo(C.TIME_UNSET);
      }
  
      // This frame should establish sync.
      framePresentationTimestampNs += halfFrameRateDuration;
      estimator.onNextFrame(framePresentationTimestampNs);
  
      assertThat(estimator.isSynced()).isTrue();
      assertThat(estimator.getFrameDurationNs()).isEqualTo(halfFrameRateDuration);
    }
  
    @Test
    public void fixedFrameRate_withMillisecondPrecision_syncs() {
      long frameDurationNs = 33_333_333;
      FixedFrameRateEstimator estimator = new FixedFrameRateEstimator();
  
      // Initial frame.
      long framePresentationTimestampNs = 0;
      estimator.onNextFrame(getNsWithMsPrecision(framePresentationTimestampNs));
  
      assertThat(estimator.isSynced()).isFalse();
      assertThat(estimator.getFrameDurationNs()).isEqualTo(C.TIME_UNSET);
  
      // Frames with consistent durations, working toward establishing sync.
      for (int i = 0; i < CONSECUTIVE_MATCHING_FRAME_DURATIONS_FOR_SYNC - 1; i++) {
        framePresentationTimestampNs += frameDurationNs;
        estimator.onNextFrame(getNsWithMsPrecision(framePresentationTimestampNs));
  
        assertThat(estimator.isSynced()).isFalse();
        assertThat(estimator.getFrameDurationNs()).isEqualTo(C.TIME_UNSET);
      }
  
      // This frame should establish sync.
      framePresentationTimestampNs += frameDurationNs;
      estimator.onNextFrame(getNsWithMsPrecision(framePresentationTimestampNs));
  
      assertThat(estimator.isSynced()).isTrue();
      // The estimated frame duration should be strictly better than millisecond precision.
      long estimatedFrameDurationNs = estimator.getFrameDurationNs();
      long estimatedFrameDurationErrorNs = Math.abs(estimatedFrameDurationNs - frameDurationNs);
      assertThat(estimatedFrameDurationErrorNs).isLessThan(1000000);
    }
  
    @Test
    public void variableFrameRate_doesNotSync() {
      long frameDurationNs = 33_333_333;
      FixedFrameRateEstimator estimator = new FixedFrameRateEstimator();
  
      // Initial frame.
      long framePresentationTimestampNs = 0;
      estimator.onNextFrame(framePresentationTimestampNs);
  
      assertThat(estimator.isSynced()).isFalse();
      assertThat(estimator.getFrameDurationNs()).isEqualTo(C.TIME_UNSET);
  
      for (int i = 0; i < CONSECUTIVE_MATCHING_FRAME_DURATIONS_FOR_SYNC * 10; i++) {
        framePresentationTimestampNs += frameDurationNs;
        // Adjust a frame that's just different enough, just often enough to prevent sync.
        if ((i % CONSECUTIVE_MATCHING_FRAME_DURATIONS_FOR_SYNC) == 0) {
          framePresentationTimestampNs += MAX_MATCHING_FRAME_DIFFERENCE_NS + 1;
        }
        estimator.onNextFrame(framePresentationTimestampNs);
  
        assertThat(estimator.isSynced()).isFalse();
        assertThat(estimator.getFrameDurationNs()).isEqualTo(C.TIME_UNSET);
      }
    }
  
    private static final long getNsWithMsPrecision(long presentationTimeNs) {
      return (presentationTimeNs / 1000000) * 1000000;
    }
  }
  