Support selecting audio tracks

Implements audio track selection on iOS & Android ExoPlayer. The prop mirrors the API for selectedTextTrack.

ios/RCTVideo.m

@@ -47,6 +47,7 @@ static NSString *const timedMetadata = @"timedMetadata";
   BOOL _allowsExternalPlayback;
   NSArray * _textTracks;
   NSDictionary * _selectedTextTrack;
+  NSDictionary * _selectedAudioTrack;
   BOOL _playbackStalled;
   BOOL _playInBackground;
   BOOL _playWhenInactive;
@@ -498,6 +499,7 @@ static NSString *const timedMetadata = @"timedMetadata";
                                  @"height": height,
                                  @"orientation": orientation
                                  },
+                             @"audioTracks": [self getAudioTrackInfo],
                              @"textTracks": [self getTextTrackInfo],
                              @"target": self.reactTag});
         }
@@ -729,6 +731,7 @@ static NSString *const timedMetadata = @"timedMetadata";
     [_player setMuted:NO];
   }
 
+  [self setSelectedAudioTrack:_selectedAudioTrack];
   [self setSelectedTextTrack:_selectedTextTrack];
   [self setResizeMode:_resizeMode];
   [self setRepeat:_repeat];
@@ -741,12 +744,64 @@ static NSString *const timedMetadata = @"timedMetadata";
   _repeat = repeat;
 }
 
+- (void)setMediaSelectionTrackForCharacteristic:(AVMediaCharacteristic)characteristic
+                                   withCriteria:(NSDictionary *)criteria
+{
+    NSString *type = criteria[@"type"];
+    AVMediaSelectionGroup *group = [_player.currentItem.asset
+                                    mediaSelectionGroupForMediaCharacteristic:characteristic];
+    AVMediaSelectionOption *mediaOption;
+    
+    if ([type isEqualToString:@"disabled"]) {
+        // Do nothing. We want to ensure option is nil
+    } else if ([type isEqualToString:@"language"] || [type isEqualToString:@"title"]) {
+        NSString *value = criteria[@"value"];
+        for (int i = 0; i < group.options.count; ++i) {
+            AVMediaSelectionOption *currentOption = [group.options objectAtIndex:i];
+            NSString *optionValue;
+            if ([type isEqualToString:@"language"]) {
+                optionValue = [currentOption extendedLanguageTag];
+            } else {
+                optionValue = [[[currentOption commonMetadata]
+                                valueForKey:@"value"]
+                               objectAtIndex:0];
+            }
+            if ([value isEqualToString:optionValue]) {
+                mediaOption = currentOption;
+                break;
+            }
+        }
+        //} else if ([type isEqualToString:@"default"]) {
+        //  option = group.defaultOption; */
+    } else if ([type isEqualToString:@"index"]) {
+        if ([criteria[@"value"] isKindOfClass:[NSNumber class]]) {
+            int index = [criteria[@"value"] intValue];
+            if (group.options.count > index) {
+                mediaOption = [group.options objectAtIndex:index];
+            }
+        }
+    } else { // default. invalid type or "system"
+        [_player.currentItem selectMediaOptionAutomaticallyInMediaSelectionGroup:group];
+        return;
+    }
+    
+    // If a match isn't found, option will be nil and text tracks will be disabled
+    [_player.currentItem selectMediaOption:mediaOption inMediaSelectionGroup:group];
+}
+
+- (void)setSelectedAudioTrack:(NSDictionary *)selectedAudioTrack {
+    _selectedAudioTrack = selectedAudioTrack;
+    [self setMediaSelectionTrackForCharacteristic:AVMediaCharacteristicAudible
+                                        withCriteria:_selectedAudioTrack];
+}
+
 - (void)setSelectedTextTrack:(NSDictionary *)selectedTextTrack {
   _selectedTextTrack = selectedTextTrack;
-  if (_textTracks) {
+  if (_textTracks) { // sideloaded text tracks
     [self setSideloadedText];
-  } else {
-    [self setStreamingText];
+  } else { // text tracks included in the HLS playlist
+    [self setMediaSelectionTrackForCharacteristic:AVMediaCharacteristicLegible
+                                     withCriteria:_selectedTextTrack];
   }
 }
 
@@ -869,9 +924,31 @@ static NSString *const timedMetadata = @"timedMetadata";
   if (_selectedTextTrack) [self setSelectedTextTrack:_selectedTextTrack];
 }
 
+- (NSArray *)getAudioTrackInfo
+{
+    NSMutableArray *audioTracks = [[NSMutableArray alloc] init];
+    AVMediaSelectionGroup *group = [_player.currentItem.asset
+                                    mediaSelectionGroupForMediaCharacteristic:AVMediaCharacteristicAudible];
+    for (int i = 0; i < group.options.count; ++i) {
+        AVMediaSelectionOption *currentOption = [group.options objectAtIndex:i];
+        NSString *title = @"";
+        NSArray *values = [[currentOption commonMetadata] valueForKey:@"value"];
+        if (values.count > 0) {
+            title = [values objectAtIndex:0];
+        }
+        NSString *language = [currentOption extendedLanguageTag] ? [currentOption extendedLanguageTag] : @"";
+        NSDictionary *audioTrack = @{
+                                    @"index": [NSNumber numberWithInt:i],
+                                    @"title": title,
+                                    @"language": language
+                                    };
+        [audioTracks addObject:audioTrack];
+    }
+    return audioTracks;
+}
+
 - (NSArray *)getTextTrackInfo
 {
-  
   // if sideloaded, textTracks will already be set
   if (_textTracks) return _textTracks;
   

ios/RCTVideoManager.m

@@ -25,6 +25,7 @@ RCT_EXPORT_VIEW_PROPERTY(repeat, BOOL);
 RCT_EXPORT_VIEW_PROPERTY(allowsExternalPlayback, BOOL);
 RCT_EXPORT_VIEW_PROPERTY(textTracks, NSArray);
 RCT_EXPORT_VIEW_PROPERTY(selectedTextTrack, NSDictionary);
+RCT_EXPORT_VIEW_PROPERTY(selectedAudioTrack, NSDictionary);
 RCT_EXPORT_VIEW_PROPERTY(paused, BOOL);
 RCT_EXPORT_VIEW_PROPERTY(muted, BOOL);
 RCT_EXPORT_VIEW_PROPERTY(controls, BOOL);