Add ability to know the locale of an audio stream

Getting audio tracks locales by parsing their ID or their label, should not be
done by clients, but by the extractor.

This commit adds the ability to store the Locale of an AudioStream, which is
used to compare similar AudioStreams (in the equalStats method).

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

@@ -25,6 +25,7 @@ import org.schabi.newpipe.extractor.services.youtube.ItagItem;
 
 import javax.annotation.Nonnull;
 import javax.annotation.Nullable;
+import java.util.Locale;
 import java.util.Objects;
 
 public final class AudioStream extends Stream {
@@ -47,6 +48,8 @@ public final class AudioStream extends Stream {
     private final String audioTrackId;
     @Nullable
     private final String audioTrackName;
+    @Nullable
+    private final Locale audioLocale;
     private final boolean isDescriptive;
 
     @Nullable
@@ -70,6 +73,8 @@ public final class AudioStream extends Stream {
         private String audioTrackId;
         @Nullable
         private String audioTrackName;
+        @Nullable
+        private Locale audioLocale;
         private boolean isDescriptive;
         @Nullable
         private ItagItem itagItem;
@@ -240,6 +245,21 @@ public final class AudioStream extends Stream {
             return this;
         }
 
+        /**
+         * Set the {@link Locale} of the audio which represents its language.
+         *
+         * <p>
+         * The default value is {@code null}, which means that the {@link Locale} is unknown.
+         * </p>
+         *
+         * @param audioLocale the {@link Locale} of the audio, which could be {@code null}
+         * @return this {@link Builder} instance
+         */
+        public Builder setAudioLocale(@Nullable final Locale audioLocale) {
+            this.audioLocale = audioLocale;
+            return this;
+        }
+
         /**
          * Set the {@link ItagItem} corresponding to the {@link AudioStream}.
          *
@@ -293,7 +313,8 @@ public final class AudioStream extends Stream {
             }
 
             return new AudioStream(id, content, isUrl, mediaFormat, deliveryMethod, averageBitrate,
-                    manifestUrl, audioTrackId, audioTrackName, isDescriptive, itagItem);
+                    manifestUrl, audioTrackId, audioTrackName, audioLocale, isDescriptive,
+                    itagItem);
         }
     }
 
@@ -313,6 +334,7 @@ public final class AudioStream extends Stream {
      *                       {@link #UNKNOWN_BITRATE})
      * @param audioTrackId   the id of the audio track
      * @param audioTrackName the name of the audio track
+     * @param audioLocale    the {@link Locale} of the audio stream, representing its language
      * @param itagItem       the {@link ItagItem} corresponding to the stream, which cannot be null
      * @param manifestUrl    the URL of the manifest this stream comes from (if applicable,
      *                       otherwise null)
@@ -327,6 +349,7 @@ public final class AudioStream extends Stream {
                         @Nullable final String manifestUrl,
                         @Nullable final String audioTrackId,
                         @Nullable final String audioTrackName,
+                        @Nullable final Locale audioLocale,
                         final boolean isDescriptive,
                         @Nullable final ItagItem itagItem) {
         super(id, content, isUrl, format, deliveryMethod, manifestUrl);
@@ -344,6 +367,7 @@ public final class AudioStream extends Stream {
         this.averageBitrate = averageBitrate;
         this.audioTrackId = audioTrackId;
         this.audioTrackName = audioTrackName;
+        this.audioLocale = audioLocale;
         this.isDescriptive = isDescriptive;
     }
 
@@ -355,7 +379,8 @@ public final class AudioStream extends Stream {
         return super.equalStats(cmp) && cmp instanceof AudioStream
                 && averageBitrate == ((AudioStream) cmp).averageBitrate
                 && Objects.equals(audioTrackId, ((AudioStream) cmp).audioTrackId)
-                && isDescriptive == ((AudioStream) cmp).isDescriptive;
+                && isDescriptive == ((AudioStream) cmp).isDescriptive
+                && Objects.equals(audioLocale, ((AudioStream) cmp).audioLocale);
     }
 
     /**
@@ -470,6 +495,17 @@ public final class AudioStream extends Stream {
         return audioTrackName;
     }
 
+    /**
+     * Get the {@link Locale} of the audio representing the language of the stream, which is
+     * {@code null} if the audio language of this stream is not known.
+     *
+     * @return the {@link Locale} of the audio or {@code null}
+     */
+    @Nullable
+    public Locale getAudioLocale() {
+        return audioLocale;
+    }
+
     /**
      * Returns whether this stream is a descriptive audio.
      *