Add unit tests for buffer-based ABR.

PiperOrigin-RevId: 237803831

library/core/src/main/java/com/google/android/exoplayer2/trackselection/BufferSizeAdaptationBuilder.java

@@ -114,7 +114,7 @@ public final class BufferSizeAdaptationBuilder {
   private int startUpMinBufferForQualityIncreaseMs;
   @Nullable private PriorityTaskManager priorityTaskManager;
   private DynamicFormatFilter dynamicFormatFilter;
-  boolean buildCalled;
+  private boolean buildCalled;
 
   /** Creates builder with default values. */
   public BufferSizeAdaptationBuilder() {
@@ -434,7 +434,7 @@ public final class BufferSizeAdaptationBuilder {
       int lowestBitrateNonBlacklistedIndex = 0;
       for (int i = 0; i < formatBitrates.length; i++) {
         if (formatBitrates[i] != BITRATE_BLACKLISTED) {
-          if (getTargetBufferForBitrateUs(formatBitrates[i]) < bufferUs
+          if (getTargetBufferForBitrateUs(formatBitrates[i]) <= bufferUs
               && dynamicFormatFilter.isFormatAllowed(
                   getFormat(i), formatBitrates[i], /* isInitialSelection= */ false)) {
             return i;

library/core/src/test/java/com/google/android/exoplayer2/trackselection/BufferSizeAdaptiveTrackSelectionTest.java

@@ -0,0 +1,248 @@
+/*
+ * Copyright (C) 2019 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.trackselection;
+
+import static com.google.common.truth.Truth.assertThat;
+import static org.mockito.Mockito.when;
+import static org.mockito.MockitoAnnotations.initMocks;
+
+import android.util.Pair;
+import com.google.android.exoplayer2.C;
+import com.google.android.exoplayer2.Format;
+import com.google.android.exoplayer2.LoadControl;
+import com.google.android.exoplayer2.source.TrackGroup;
+import com.google.android.exoplayer2.source.chunk.MediaChunkIterator;
+import com.google.android.exoplayer2.upstream.BandwidthMeter;
+import com.google.android.exoplayer2.util.MimeTypes;
+import java.util.Collections;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.robolectric.RobolectricTestRunner;
+
+/** Unit test for the track selection created by {@link BufferSizeAdaptationBuilder}. */
+@RunWith(RobolectricTestRunner.class)
+public final class BufferSizeAdaptiveTrackSelectionTest {
+
+  private static final int MIN_BUFFER_MS = 15_000;
+  private static final int MAX_BUFFER_MS = 50_000;
+  private static final int HYSTERESIS_BUFFER_MS = 10_000;
+  private static final float BANDWIDTH_FRACTION = 0.5f;
+  private static final int MIN_BUFFER_FOR_QUALITY_INCREASE_MS = 10_000;
+
+  /**
+   * Factor between bitrates is always the same (=2.2). That means buffer levels should be linearly
+   * distributed between MIN_BUFFER=15s and MAX_BUFFER-HYSTERESIS=50s-10s=40s.
+   */
+  private static final Format format1 =
+      createVideoFormat(/* bitrate= */ 500, /* width= */ 320, /* height= */ 240);
+
+  private static final Format format2 =
+      createVideoFormat(/* bitrate= */ 1100, /* width= */ 640, /* height= */ 480);
+  private static final Format format3 =
+      createVideoFormat(/* bitrate= */ 2420, /* width= */ 960, /* height= */ 720);
+  private static final int BUFFER_LEVEL_FORMAT_2 =
+      (MIN_BUFFER_MS + MAX_BUFFER_MS - HYSTERESIS_BUFFER_MS) / 2;
+  private static final int BUFFER_LEVEL_FORMAT_3 = MAX_BUFFER_MS - HYSTERESIS_BUFFER_MS;
+
+  @Mock private BandwidthMeter mockBandwidthMeter;
+  private TrackSelection trackSelection;
+
+  @Before
+  public void setUp() {
+    initMocks(this);
+    Pair<TrackSelection.Factory, LoadControl> trackSelectionFactoryAndLoadControl =
+        new BufferSizeAdaptationBuilder()
+            .setBufferDurationsMs(
+                MIN_BUFFER_MS,
+                MAX_BUFFER_MS,
+                /* bufferForPlaybackMs= */ 1000,
+                /* bufferForPlaybackAfterRebufferMs= */ 1000)
+            .setHysteresisBufferMs(HYSTERESIS_BUFFER_MS)
+            .setStartUpTrackSelectionParameters(
+                BANDWIDTH_FRACTION, MIN_BUFFER_FOR_QUALITY_INCREASE_MS)
+            .buildPlayerComponents();
+    trackSelection =
+        trackSelectionFactoryAndLoadControl
+            .first
+            .createTrackSelections(
+                new TrackSelection.Definition[] {
+                  new TrackSelection.Definition(
+                      new TrackGroup(format1, format2, format3), /* tracks= */ 0, 1, 2)
+                },
+                mockBandwidthMeter)[0];
+    trackSelection.enable();
+  }
+
+  @Test
+  public void updateSelectedTrack_usesBandwidthEstimateForInitialSelection() {
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format2));
+
+    updateSelectedTrack(/* bufferedDurationMs= */ 0);
+
+    assertThat(trackSelection.getSelectedFormat()).isEqualTo(format2);
+    assertThat(trackSelection.getSelectionReason()).isEqualTo(C.SELECTION_REASON_INITIAL);
+  }
+
+  @Test
+  public void updateSelectedTrack_withLowerBandwidthEstimateDuringStartUp_switchesDown() {
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format2));
+    updateSelectedTrack(/* bufferedDurationMs= */ 0);
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(0L);
+
+    updateSelectedTrack(/* bufferedDurationMs= */ 0);
+
+    assertThat(trackSelection.getSelectedFormat()).isEqualTo(format1);
+    assertThat(trackSelection.getSelectionReason()).isEqualTo(C.SELECTION_REASON_ADAPTIVE);
+  }
+
+  @Test
+  public void
+      updateSelectedTrack_withHigherBandwidthEstimateDuringStartUp_andLowBuffer_keepsSelection() {
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format2));
+    updateSelectedTrack(/* bufferedDurationMs= */ 0);
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format3));
+
+    updateSelectedTrack(/* bufferedDurationMs= */ MIN_BUFFER_FOR_QUALITY_INCREASE_MS - 1);
+
+    assertThat(trackSelection.getSelectedFormat()).isEqualTo(format2);
+    assertThat(trackSelection.getSelectionReason()).isEqualTo(C.SELECTION_REASON_INITIAL);
+  }
+
+  @Test
+  public void
+      updateSelectedTrack_withHigherBandwidthEstimateDuringStartUp_andHighBuffer_switchesUp() {
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format2));
+    updateSelectedTrack(/* bufferedDurationMs= */ 0);
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format3));
+
+    updateSelectedTrack(/* bufferedDurationMs= */ MIN_BUFFER_FOR_QUALITY_INCREASE_MS);
+
+    assertThat(trackSelection.getSelectedFormat()).isEqualTo(format3);
+    assertThat(trackSelection.getSelectionReason()).isEqualTo(C.SELECTION_REASON_ADAPTIVE);
+  }
+
+  @Test
+  public void
+      updateSelectedTrack_withIncreasedBandwidthEstimate_onceSteadyStateBufferIsReached_keepsSelection() {
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format2));
+    updateSelectedTrack(/* bufferedDurationMs= */ 0);
+    updateSelectedTrack(/* bufferedDurationMs= */ BUFFER_LEVEL_FORMAT_2);
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format3));
+
+    updateSelectedTrack(/* bufferedDurationMs= */ BUFFER_LEVEL_FORMAT_2);
+
+    assertThat(trackSelection.getSelectedFormat()).isEqualTo(format2);
+    assertThat(trackSelection.getSelectionReason()).isEqualTo(C.SELECTION_REASON_INITIAL);
+  }
+
+  @Test
+  public void
+      updateSelectedTrack_withDecreasedBandwidthEstimate_onceSteadyStateBufferIsReached_keepsSelection() {
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format2));
+    updateSelectedTrack(/* bufferedDurationMs= */ 0);
+    updateSelectedTrack(/* bufferedDurationMs= */ BUFFER_LEVEL_FORMAT_2);
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(0L);
+
+    updateSelectedTrack(/* bufferedDurationMs= */ BUFFER_LEVEL_FORMAT_2);
+
+    assertThat(trackSelection.getSelectedFormat()).isEqualTo(format2);
+    assertThat(trackSelection.getSelectionReason()).isEqualTo(C.SELECTION_REASON_INITIAL);
+  }
+
+  @Test
+  public void updateSelectedTrack_withIncreasedBufferInSteadyState_switchesUp() {
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format2));
+    updateSelectedTrack(/* bufferedDurationMs= */ 0);
+    updateSelectedTrack(/* bufferedDurationMs= */ BUFFER_LEVEL_FORMAT_2);
+
+    updateSelectedTrack(/* bufferedDurationMs= */ BUFFER_LEVEL_FORMAT_3);
+
+    assertThat(trackSelection.getSelectedFormat()).isEqualTo(format3);
+    assertThat(trackSelection.getSelectionReason()).isEqualTo(C.SELECTION_REASON_ADAPTIVE);
+  }
+
+  @Test
+  public void updateSelectedTrack_withDecreasedBufferInSteadyState_switchesDown() {
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format2));
+    updateSelectedTrack(/* bufferedDurationMs= */ 0);
+    updateSelectedTrack(/* bufferedDurationMs= */ BUFFER_LEVEL_FORMAT_2);
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(0L);
+
+    updateSelectedTrack(/* bufferedDurationMs= */ BUFFER_LEVEL_FORMAT_2 - HYSTERESIS_BUFFER_MS - 1);
+
+    assertThat(trackSelection.getSelectedFormat()).isEqualTo(format1);
+    assertThat(trackSelection.getSelectionReason()).isEqualTo(C.SELECTION_REASON_ADAPTIVE);
+  }
+
+  @Test
+  public void
+      updateSelectedTrack_withDecreasedBufferInSteadyState_withinHysteresis_keepsSelection() {
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format2));
+    updateSelectedTrack(/* bufferedDurationMs= */ 0);
+    updateSelectedTrack(/* bufferedDurationMs= */ BUFFER_LEVEL_FORMAT_2);
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(0L);
+
+    updateSelectedTrack(/* bufferedDurationMs= */ BUFFER_LEVEL_FORMAT_2 - HYSTERESIS_BUFFER_MS);
+
+    assertThat(trackSelection.getSelectedFormat()).isEqualTo(format2);
+    assertThat(trackSelection.getSelectionReason()).isEqualTo(C.SELECTION_REASON_INITIAL);
+  }
+
+  @Test
+  public void onDiscontinuity_switchesBackToStartUpState() {
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(getBitrateEstimateEnoughFor(format2));
+    updateSelectedTrack(/* bufferedDurationMs= */ 0);
+    updateSelectedTrack(/* bufferedDurationMs= */ BUFFER_LEVEL_FORMAT_2);
+    when(mockBandwidthMeter.getBitrateEstimate()).thenReturn(0L);
+
+    trackSelection.onDiscontinuity();
+    updateSelectedTrack(/* bufferedDurationMs= */ BUFFER_LEVEL_FORMAT_2 - 1);
+
+    assertThat(trackSelection.getSelectedFormat()).isEqualTo(format1);
+    assertThat(trackSelection.getSelectionReason()).isEqualTo(C.SELECTION_REASON_ADAPTIVE);
+  }
+
+  private void updateSelectedTrack(long bufferedDurationMs) {
+    trackSelection.updateSelectedTrack(
+        /* playbackPositionUs= */ 0,
+        /* bufferedDurationUs= */ C.msToUs(bufferedDurationMs),
+        /* availableDurationUs= */ C.TIME_UNSET,
+        /* queue= */ Collections.emptyList(),
+        /* mediaChunkIterators= */ new MediaChunkIterator[] {
+          MediaChunkIterator.EMPTY, MediaChunkIterator.EMPTY, MediaChunkIterator.EMPTY
+        });
+  }
+
+  private static Format createVideoFormat(int bitrate, int width, int height) {
+    return Format.createVideoSampleFormat(
+        /* id= */ null,
+        /* sampleMimeType= */ MimeTypes.VIDEO_H264,
+        /* codecs= */ null,
+        /* bitrate= */ bitrate,
+        /* maxInputSize= */ Format.NO_VALUE,
+        /* width= */ width,
+        /* height= */ height,
+        /* frameRate= */ Format.NO_VALUE,
+        /* initializationData= */ null,
+        /* drmInitData= */ null);
+  }
+
+  private static long getBitrateEstimateEnoughFor(Format format) {
+    return (long) (format.bitrate / BANDWIDTH_FRACTION) + 1;
+  }
+}