From 3bd59f8cf05152edd404e60a2ce26cc0eabb8f3a Mon Sep 17 00:00:00 2001
From: tonihei <tonihei@google.com>
Date: Tue, 13 Apr 2021 15:06:07 +0100
Subject: [PATCH] Ensure minDurationToRetainAfterDiscard >=
 minDurationForQualityIncrease

If this condition isn't true, the player may enter a cycle of discarding
and reloading the same format. As minDurationToRetainAfterDiscard is a
parameter likely left at its default, and minDurationForQualityIncrease
is likely adjusted more often, we correct the value in the problematic
case and log a warning instead of asserting it outright to prevent
unnecessary app breakages.

Issue: #8807
PiperOrigin-RevId: 368207417
---
 .../trackselection/AdaptiveTrackSelection.java | 18 +++++++++++++++---
 1 file changed, 15 insertions(+), 3 deletions(-)

diff --git a/library/core/src/main/java/com/google/android/exoplayer2/trackselection/AdaptiveTrackSelection.java b/library/core/src/main/java/com/google/android/exoplayer2/trackselection/AdaptiveTrackSelection.java
index e02f8198d5..18a71cbf2f 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/trackselection/AdaptiveTrackSelection.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/trackselection/AdaptiveTrackSelection.java
@@ -26,6 +26,7 @@ import com.google.android.exoplayer2.source.chunk.MediaChunk;
 import com.google.android.exoplayer2.source.chunk.MediaChunkIterator;
 import com.google.android.exoplayer2.upstream.BandwidthMeter;
 import com.google.android.exoplayer2.util.Clock;
+import com.google.android.exoplayer2.util.Log;
 import com.google.android.exoplayer2.util.Util;
 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.Iterables;
@@ -42,6 +43,8 @@ import org.checkerframework.checker.nullness.compatqual.NullableType;
  */
 public class AdaptiveTrackSelection extends BaseTrackSelection {
 
+  private static final String TAG = "AdaptiveTrackSelection";
+
   /** Factory for {@link AdaptiveTrackSelection} instances. */
   public static class Factory implements ExoTrackSelection.Factory {
 
@@ -73,7 +76,8 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
      * @param minDurationToRetainAfterDiscardMs When switching to a track of significantly higher
      *     quality, the selection may indicate that media already buffered at the lower quality can
      *     be discarded to speed up the switch. This is the minimum duration of media that must be
-     *     retained at the lower quality.
+     *     retained at the lower quality. It must be at least {@code
+     *     minDurationForQualityIncreaseMs}.
      * @param bandwidthFraction The fraction of the available bandwidth that the selection should
      *     consider available for use. Setting to a value less than 1 is recommended to account for
      *     inaccuracies in the bandwidth estimator.
@@ -102,7 +106,8 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
      * @param minDurationToRetainAfterDiscardMs When switching to a track of significantly higher
      *     quality, the selection may indicate that media already buffered at the lower quality can
      *     be discarded to speed up the switch. This is the minimum duration of media that must be
-     *     retained at the lower quality.
+     *     retained at the lower quality. It must be at least {@code
+     *     minDurationForQualityIncreaseMs}.
      * @param bandwidthFraction The fraction of the available bandwidth that the selection should
      *     consider available for use. Setting to a value less than 1 is recommended to account for
      *     inaccuracies in the bandwidth estimator.
@@ -249,7 +254,7 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
    * @param minDurationToRetainAfterDiscardMs When switching to a track of significantly higher
    *     quality, the selection may indicate that media already buffered at the lower quality can be
    *     discarded to speed up the switch. This is the minimum duration of media that must be
-   *     retained at the lower quality.
+   *     retained at the lower quality. It must be at least {@code minDurationForQualityIncreaseMs}.
    * @param bandwidthFraction The fraction of the available bandwidth that the selection should
    *     consider available for use. Setting to a value less than 1 is recommended to account for
    *     inaccuracies in the bandwidth estimator.
@@ -276,6 +281,13 @@ public class AdaptiveTrackSelection extends BaseTrackSelection {
       List<AdaptationCheckpoint> adaptationCheckpoints,
       Clock clock) {
     super(group, tracks, type);
+    if (minDurationToRetainAfterDiscardMs < minDurationForQualityIncreaseMs) {
+      Log.w(
+          TAG,
+          "Adjusting minDurationToRetainAfterDiscardMs to be at least"
+              + " minDurationForQualityIncreaseMs");
+      minDurationToRetainAfterDiscardMs = minDurationForQualityIncreaseMs;
+    }
     this.bandwidthMeter = bandwidthMeter;
     this.minDurationForQualityIncreaseUs = minDurationForQualityIncreaseMs * 1000L;
     this.maxDurationForQualityDecreaseUs = maxDurationForQualityDecreaseMs * 1000L;