[YouTube] Add support for extracting auto-translated captions

Closes #977
Based on and adresses TeamNewPipe/NewPipe#8023

Author: TobiGr

extractor/src/main/java/org/schabi/newpipe/extractor/services/peertube/extractors/PeertubeStreamExtractor.java

@@ -476,6 +476,7 @@ private void loadSubtitles() {
                                     .setMediaFormat(fmt)
                                     .setLanguageCode(languageCode)
                                     .setAutoGenerated(false)
+                                    .setAutoTranslated(false)
                                     .build());
                         }
                     }

extractor/src/main/java/org/schabi/newpipe/extractor/services/youtube/extractors/YoutubeStreamExtractor.java

@@ -665,21 +665,21 @@ public List<SubtitlesStream> getSubtitlesDefault() throws ParsingException {
 
     @Override
     @Nonnull
-    public List<SubtitlesStream> getSubtitles(final MediaFormat format) throws ParsingException {
+    public List<SubtitlesStream> getSubtitles(@Nonnull final MediaFormat format)
+            throws ParsingException {
         assertPageFetched();
 
         // We cannot store the subtitles list because the media format may change
         final List<SubtitlesStream> subtitlesToReturn = new ArrayList<>();
         final JsonObject renderer = playerResponse.getObject("captions")
                 .getObject("playerCaptionsTracklistRenderer");
         final JsonArray captionsArray = renderer.getArray("captionTracks");
-        // TODO: use this to apply auto translation to different language from a source language
-        // final JsonArray autoCaptionsArray = renderer.getArray("translationLanguages");
 
         for (int i = 0; i < captionsArray.size(); i++) {
-            final String languageCode = captionsArray.getObject(i).getString("languageCode");
-            final String baseUrl = captionsArray.getObject(i).getString("baseUrl");
-            final String vssId = captionsArray.getObject(i).getString("vssId");
+            final JsonObject caption = captionsArray.getObject(i);
+            final String languageCode = caption.getString("languageCode");
+            final String baseUrl = caption.getString("baseUrl");
+            final String vssId = caption.getString("vssId");
 
             if (languageCode != null && baseUrl != null && vssId != null) {
                 final boolean isAutoGenerated = vssId.startsWith("a.");
@@ -694,7 +694,24 @@ public List<SubtitlesStream> getSubtitles(final MediaFormat format) throws Parsi
                         .setMediaFormat(format)
                         .setLanguageCode(languageCode)
                         .setAutoGenerated(isAutoGenerated)
+                        .setAutoTranslated(false)
                         .build());
+                if (i == 0 && caption.getBoolean("isTranslatable")
+                        && renderer.has("translationLanguages")) {
+                    final JsonArray languages = renderer.getArray("translationLanguages");
+                    for (int j = 0; j < languages.size(); j++) {
+                        final JsonObject lang = languages.getObject(j);
+                        final String tLanguageCode = lang.getString("languageCode");
+                        subtitlesToReturn.add(new SubtitlesStream.Builder()
+                                .setContent(cleanUrl + "&fmt=" + format.getSuffix()
+                                        + "&tlang=" + tLanguageCode, true)
+                                .setMediaFormat(format)
+                                .setLanguageCode(tLanguageCode)
+                                .setAutoGenerated(isAutoGenerated)
+                                .setAutoTranslated(true)
+                                .build());
+                    }
+                }
             }
         }
 

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

@@ -14,6 +14,7 @@ public final class SubtitlesStream extends Stream {
     private final MediaFormat format;
     private final Locale locale;
     private final boolean autoGenerated;
+    private final boolean autoTranslated;
     private final String code;
 
     /**
@@ -32,6 +33,7 @@ public static final class Builder {
         private String languageCode;
         // Use of the Boolean class instead of the primitive type needed for setter call check
         private Boolean autoGenerated;
+        private Boolean autoTranslated;
 
         /**
          * Create a new {@link Builder} instance with default values.
@@ -152,6 +154,18 @@ public Builder setAutoGenerated(final boolean autoGenerated) {
             return this;
         }
 
+        /**
+         * Set whether the subtitles have been automatically translated
+         * (i.e. by a machine like Google Translator) by the streaming service.
+         * @param autoTranslated whether the subtitles have been automatically translated by the
+         *                       streaming service
+         * @return this {@link Builder} instance
+         */
+        public Builder setAutoTranslated(final boolean autoTranslated) {
+            this.autoTranslated = autoTranslated;
+            return this;
+        }
+
         /**
          * Build a {@link SubtitlesStream} using the builder's current values.
          *
@@ -196,13 +210,19 @@ public SubtitlesStream build() throws ParsingException {
                         + "with setIsAutoGenerated.");
             }
 
+            if (autoTranslated == null) {
+                throw new IllegalStateException("The subtitles stream has been not set as an "
+                        + "automatically translated subtitles stream or not. "
+                        + "Please specify this information  with setIsAutoTranslated.");
+            }
+
             if (id == null) {
                 id = languageCode + (mediaFormat != null ? "." + mediaFormat.suffix
                         : "");
             }
 
             return new SubtitlesStream(id, content, isUrl, mediaFormat, deliveryMethod,
-                    languageCode, autoGenerated, manifestUrl);
+                    languageCode, autoGenerated, autoTranslated, manifestUrl);
         }
     }
 
@@ -219,6 +239,7 @@ public SubtitlesStream build() throws ParsingException {
      * @param deliveryMethod the {@link DeliveryMethod} of the stream
      * @param languageCode   the language code of the stream
      * @param autoGenerated  whether the subtitles are auto-generated by the streaming service
+     * @param autoTranslated whether the subtitles are auto-translated by the streaming service
      * @param manifestUrl    the URL of the manifest this stream comes from (if applicable,
      *                       otherwise null)
      */
@@ -230,6 +251,7 @@ private SubtitlesStream(@Nonnull final String id,
                             @Nonnull final DeliveryMethod deliveryMethod,
                             @Nonnull final String languageCode,
                             final boolean autoGenerated,
+                            final boolean autoTranslated,
                             @Nullable final String manifestUrl) throws ParsingException {
         super(id, content, isUrl, mediaFormat, deliveryMethod, manifestUrl);
         this.locale = LocaleCompat.forLanguageTag(languageCode).orElseThrow(
@@ -238,6 +260,7 @@ private SubtitlesStream(@Nonnull final String id,
         this.code = languageCode;
         this.format = mediaFormat;
         this.autoGenerated = autoGenerated;
+        this.autoTranslated = autoTranslated;
     }
 
     /**
@@ -250,7 +273,7 @@ public String getExtension() {
     }
 
     /**
-     * Return whether if the subtitles are auto-generated.
+     * Return whether the subtitles are auto-generated.
      * <p>
      * Some streaming services can generate subtitles for their contents, like YouTube.
      * </p>
@@ -261,6 +284,21 @@ public boolean isAutoGenerated() {
         return autoGenerated;
     }
 
+    /**
+     * Whether the subtitles are translated automatically by a machine.
+     *
+     * <p>
+     * Some streaming services provide automatically translated subtitles.
+     * YouTube, for example, uses Google translator to generate translated subtitles.
+     * Automatically translated subtitles might not coincide completely with the original text.
+     * </p>
+     *
+     * @return {code true} if the subtitles are auto-translated, {@link false} otherwise
+     */
+    public boolean isAutoTranslated() {
+        return autoTranslated;
+    }
+
     /**
      * {@inheritDoc}
      */