fix: docstrings

extractor/src/main/java/org/schabi/newpipe/extractor/services/youtube/dashmanifestcreators/YoutubeDashManifestCreatorsUtils.java

@@ -324,8 +324,9 @@ public final class YoutubeDashManifestCreatorsUtils {
                     return "dub";
                 case DESCRIPTIVE:
                     return "description";
+                default:
+                    return "alternate";
             }
-            return "alternate";
         }
         return "main";
     }

extractor/src/main/java/org/schabi/newpipe/extractor/stream/AudioStream.java

@@ -500,6 +500,12 @@ public final class AudioStream extends Stream {
         return audioLocale;
     }
 
+    /**
+     * Get the {@link AudioTrackType} of the stream, which is {@code null} if the track type
+     * is not known.
+     *
+     * @return the {@link AudioTrackType} of the stream or {@code null}
+     */
     @Nullable
     public AudioTrackType getAudioTrackType() {
         return audioTrackType;

extractor/src/main/java/org/schabi/newpipe/extractor/stream/AudioTrackType.java

@@ -6,12 +6,12 @@ package org.schabi.newpipe.extractor.stream;
  */
 public enum AudioTrackType {
     /**
-     * The original audio track of the video
+     * An original audio track of the video.
      */
     ORIGINAL,
 
     /**
-     * Audio track with the original voices replaced, typically in a different language
+     * An audio track with the original voices replaced, typically in a different language.
      *
      * @see <a href="https://en.wikipedia.org/wiki/Dubbing">
      * https://en.wikipedia.org/wiki/Dubbing</a>
@@ -19,11 +19,11 @@ public enum AudioTrackType {
     DUBBED,
 
     /**
-     * Descriptive audio
+     * A descriptive audio track.
      * <p>
-     * A descriptive audio is an audio in which descriptions of visual elements of a video are
-     * added in the original audio, with the goal to make a video more accessible to blind and
-     * visually impaired people.
+     * A descriptive audio track is an audio track in which descriptions of visual elements of
+     * a video are added to the original audio, with the goal to make a video more accessible to
+     * blind and visually impaired people.
      * </p>
      *
      * @see <a href="https://en.wikipedia.org/wiki/Audio_description">