Fix detection of Dolby Atmos in HLS

E-AC3 with JOC is signaled using the CHANNELS attribute for HLS:
https://developer.apple.com/documentation/http_live_streaming/hls_authoring_specification_for_apple_devices/hls_authoring_specification_for_apple_devices_appendices

PiperOrigin-RevId: 277680300

RELEASENOTES.md

@@ -105,6 +105,7 @@
 * Deprecate the GVR extension.
 * Fix the start of audio getting truncated when transitioning to a new
   item in a playlist of opus streams.
+* Fix detection of Dolby Atmos in HLS to match the HLS authoring specification.
 
 ### 2.10.6 (2019-10-17) ###
 

library/hls/src/main/java/com/google/android/exoplayer2/source/hls/playlist/HlsPlaylistParser.java

@@ -452,7 +452,15 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
                   ? Util.getCodecsOfType(variant.format.codecs, C.TRACK_TYPE_AUDIO)
                   : null;
           sampleMimeType = codecs != null ? MimeTypes.getMediaMimeType(codecs) : null;
-          int channelCount = parseChannelsAttribute(line, variableDefinitions);
+          String channelsString =
+              parseOptionalStringAttr(line, REGEX_CHANNELS, variableDefinitions);
+          int channelCount = Format.NO_VALUE;
+          if (channelsString != null) {
+            channelCount = Integer.parseInt(Util.splitAtFirst(channelsString, "/")[0]);
+            if (MimeTypes.AUDIO_E_AC3.equals(sampleMimeType) && channelsString.endsWith("/JOC")) {
+              sampleMimeType = MimeTypes.AUDIO_E_AC3_JOC;
+            }
+          }
           format =
               Format.createAudioContainerFormat(
                   /* id= */ formatId,
@@ -828,13 +836,6 @@ public final class HlsPlaylistParser implements ParsingLoadable.Parser<HlsPlayli
     return roleFlags;
   }
 
-  private static int parseChannelsAttribute(String line, Map<String, String> variableDefinitions) {
-    String channelsString = parseOptionalStringAttr(line, REGEX_CHANNELS, variableDefinitions);
-    return channelsString != null
-        ? Integer.parseInt(Util.splitAtFirst(channelsString, "/")[0])
-        : Format.NO_VALUE;
-  }
-
   @Nullable
   private static SchemeData parseDrmSchemeData(
       String line, String keyFormat, Map<String, String> variableDefinitions)