From 23c07e5c4d1077e67087fa80d8b27d571cf5a60b Mon Sep 17 00:00:00 2001
From: tonihei <tonihei@google.com>
Date: Fri, 18 Jan 2019 14:57:10 +0000
Subject: [PATCH] Update buffer-based ABR to not select track in constructor.

This mimicks a similar change in the default AdaptiveTrackSelection.
Also adds an option to cap initial format height.

PiperOrigin-RevId: 229923149
---
 .../BufferSizeAdaptationBuilder.java          | 28 ++++++++++++-------
 1 file changed, 18 insertions(+), 10 deletions(-)

diff --git a/library/core/src/main/java/com/google/android/exoplayer2/trackselection/BufferSizeAdaptationBuilder.java b/library/core/src/main/java/com/google/android/exoplayer2/trackselection/BufferSizeAdaptationBuilder.java
index 5c8350cb1d..ee1d1c62da 100644
--- a/library/core/src/main/java/com/google/android/exoplayer2/trackselection/BufferSizeAdaptationBuilder.java
+++ b/library/core/src/main/java/com/google/android/exoplayer2/trackselection/BufferSizeAdaptationBuilder.java
@@ -43,7 +43,7 @@ public final class BufferSizeAdaptationBuilder {
   public interface DynamicFormatFilter {
 
     /** Filter which allows all formats. */
-    DynamicFormatFilter NO_FILTER = (format, trackBitrate) -> true;
+    DynamicFormatFilter NO_FILTER = (format, trackBitrate, isInitialSelection) -> true;
 
     /**
      * Called when updating the selected track to determine whether a candidate track is allowed. If
@@ -52,8 +52,9 @@ public final class BufferSizeAdaptationBuilder {
      * @param format The {@link Format} of the candidate track.
      * @param trackBitrate The estimated bitrate of the track. May differ from {@link
      *     Format#bitrate} if a more accurate estimate of the current track bitrate is available.
+     * @param isInitialSelection Whether this is for the initial track selection.
      */
-    boolean isFormatAllowed(Format format, int trackBitrate);
+    boolean isFormatAllowed(Format format, int trackBitrate, boolean isInitialSelection);
   }
 
   /**
@@ -344,7 +345,7 @@ public final class BufferSizeAdaptationBuilder {
       formatBitrates = new int[length];
       maxBitrate = getFormat(/* index= */ 0).bitrate;
       minBitrate = getFormat(/* index= */ length - 1).bitrate;
-      selectionReason = C.SELECTION_REASON_INITIAL;
+      selectionReason = C.SELECTION_REASON_UNKNOWN;
       playbackSpeed = 1.0f;
 
       // We use a log-linear function to map from bitrate to buffer size:
@@ -354,9 +355,6 @@ public final class BufferSizeAdaptationBuilder {
           (maxBufferUs - hysteresisBufferUs - minBufferUs) / Math.log(maxBitrate / minBitrate);
       bitrateToBufferFunctionIntercept =
           minBufferUs - bitrateToBufferFunctionSlope * Math.log(minBitrate);
-
-      updateFormatBitrates(/* nowMs= */ Long.MIN_VALUE);
-      selectedIndex = selectIdealIndexUsingBandwidth();
     }
 
     @Override
@@ -393,6 +391,14 @@ public final class BufferSizeAdaptationBuilder {
         List<? extends MediaChunk> queue,
         MediaChunkIterator[] mediaChunkIterators) {
       updateFormatBitrates(/* nowMs= */ clock.elapsedRealtime());
+
+      // Make initial selection
+      if (selectionReason == C.SELECTION_REASON_UNKNOWN) {
+        selectionReason = C.SELECTION_REASON_INITIAL;
+        selectedIndex = selectIdealIndexUsingBandwidth(/* isInitialSelection= */ true);
+        return;
+      }
+
       long bufferUs = getCurrentPeriodBufferedDurationUs(playbackPositionUs, bufferedDurationUs);
       int oldSelectedIndex = selectedIndex;
       if (isInSteadyState) {
@@ -428,7 +434,8 @@ public final class BufferSizeAdaptationBuilder {
       for (int i = 0; i < formatBitrates.length; i++) {
         if (formatBitrates[i] != BITRATE_BLACKLISTED) {
           if (getTargetBufferForBitrateUs(formatBitrates[i]) < bufferUs
-              && dynamicFormatFilter.isFormatAllowed(getFormat(i), formatBitrates[i])) {
+              && dynamicFormatFilter.isFormatAllowed(
+                  getFormat(i), formatBitrates[i], /* isInitialSelection= */ false)) {
             return i;
           }
           lowestBitrateNonBlacklistedIndex = i;
@@ -440,7 +447,7 @@ public final class BufferSizeAdaptationBuilder {
     // Startup.
 
     private void selectIndexStartUpPhase(long bufferUs) {
-      int startUpSelectedIndex = selectIdealIndexUsingBandwidth();
+      int startUpSelectedIndex = selectIdealIndexUsingBandwidth(/* isInitialSelection= */ false);
       int steadyStateSelectedIndex = selectIdealIndexUsingBufferSize(bufferUs);
       if (steadyStateSelectedIndex <= selectedIndex) {
         // Switch to steady state if we have enough buffer to maintain current selection.
@@ -457,14 +464,15 @@ public final class BufferSizeAdaptationBuilder {
       }
     }
 
-    private int selectIdealIndexUsingBandwidth() {
+    private int selectIdealIndexUsingBandwidth(boolean isInitialSelection) {
       long effectiveBitrate =
           (long) (bandwidthMeter.getBitrateEstimate() * startUpBandwidthFraction);
       int lowestBitrateNonBlacklistedIndex = 0;
       for (int i = 0; i < formatBitrates.length; i++) {
         if (formatBitrates[i] != BITRATE_BLACKLISTED) {
           if (Math.round(formatBitrates[i] * playbackSpeed) <= effectiveBitrate
-              && dynamicFormatFilter.isFormatAllowed(getFormat(i), formatBitrates[i])) {
+              && dynamicFormatFilter.isFormatAllowed(
+                  getFormat(i), formatBitrates[i], isInitialSelection)) {
             return i;
           }
           lowestBitrateNonBlacklistedIndex = i;