From 45857b50dc251e67f7b0d609ba276a5aebf11677 Mon Sep 17 00:00:00 2001
From: olly <olly@google.com>
Date: Tue, 16 Nov 2021 14:27:18 +0000
Subject: [PATCH] HLS: Merge muxedAudioFormat into primary audio tracks

Issue: google/ExoPlayer#9608
#minor-release
PiperOrigin-RevId: 410236626
---
 RELEASENOTES.md                               |  4 +++
 .../source/hls/HlsSampleStreamWrapper.java    | 28 +++++++++++++------
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/RELEASENOTES.md b/RELEASENOTES.md
index 091a5240e6..c91933ba7c 100644
--- a/RELEASENOTES.md
+++ b/RELEASENOTES.md
@@ -2,6 +2,10 @@
 
 ### dev-v2 (not yet released)
 
+*   HLS:
+    *   Correctly populate `Format.label` for audio only HLS streams
+        ([#9608](https://github.com/google/ExoPlayer/issues/9608)).
+
 ### 2.16.1 (2021-11-11)
 
 *   Core Library:
diff --git a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsSampleStreamWrapper.java b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsSampleStreamWrapper.java
index da4fbad97d..6695c329da 100644
--- a/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsSampleStreamWrapper.java
+++ b/library/hls/src/main/java/com/google/android/exoplayer2/source/hls/HlsSampleStreamWrapper.java
@@ -1392,23 +1392,31 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
       Format sampleFormat = Assertions.checkStateNotNull(sampleQueues[i].getUpstreamFormat());
       if (i == primaryExtractorTrackIndex) {
         Format[] formats = new Format[chunkSourceTrackCount];
-        if (chunkSourceTrackCount == 1) {
-          formats[0] = sampleFormat.withManifestFormatInfo(chunkSourceTrackGroup.getFormat(0));
-        } else {
-          for (int j = 0; j < chunkSourceTrackCount; j++) {
-            formats[j] = deriveFormat(chunkSourceTrackGroup.getFormat(j), sampleFormat, true);
+        for (int j = 0; j < chunkSourceTrackCount; j++) {
+          Format playlistFormat = chunkSourceTrackGroup.getFormat(j);
+          if (primaryExtractorTrackType == C.TRACK_TYPE_AUDIO && muxedAudioFormat != null) {
+            playlistFormat = playlistFormat.withManifestFormatInfo(muxedAudioFormat);
           }
+          // If there's only a single variant (chunkSourceTrackCount == 1) then we can safely
+          // retain all fields from sampleFormat. Else we need to use deriveFormat to retain only
+          // the fields that will be the same for all variants.
+          formats[j] =
+              chunkSourceTrackCount == 1
+                  ? sampleFormat.withManifestFormatInfo(playlistFormat)
+                  : deriveFormat(playlistFormat, sampleFormat, /* propagateBitrates= */ true);
         }
         trackGroups[i] = new TrackGroup(formats);
         primaryTrackGroupIndex = i;
       } else {
         @Nullable
-        Format trackFormat =
+        Format playlistFormat =
             primaryExtractorTrackType == C.TRACK_TYPE_VIDEO
                     && MimeTypes.isAudio(sampleFormat.sampleMimeType)
                 ? muxedAudioFormat
                 : null;
-        trackGroups[i] = new TrackGroup(deriveFormat(trackFormat, sampleFormat, false));
+        trackGroups[i] =
+            new TrackGroup(
+                deriveFormat(playlistFormat, sampleFormat, /* propagateBitrates= */ false));
       }
     }
     this.trackGroups = createTrackGroupArrayWithDrmInfo(trackGroups);
@@ -1496,8 +1504,12 @@ import org.checkerframework.checker.nullness.qual.RequiresNonNull;
    * sample format that may have been obtained from a chunk belonging to a different track in the
    * same track group.
    *
+   * <p>Note: Since the sample format may have been obtained from a chunk belonging to a different
+   * track, it should not be used as a source for data that may vary between tracks.
+   *
    * @param playlistFormat The format information obtained from the master playlist.
-   * @param sampleFormat The format information obtained from the samples.
+   * @param sampleFormat The format information obtained from samples within a chunk. The chunk may
+   *     belong to a different track in the same track group.
    * @param propagateBitrates Whether the bitrates from the playlist format should be included in
    *     the derived format.
    * @return The derived track format.