Allow relaxation of TTML validity requirement when parsing subtitles.

library/src/main/java/com/google/android/exoplayer/ParserException.java

@@ -26,8 +26,12 @@ public class ParserException extends IOException {
     super(message);
   }
 
-  public ParserException(Exception cause) {
+  public ParserException(Throwable cause) {
     super(cause);
   }
 
+  public ParserException(String message, Throwable cause) {
+    super(message, cause);
+  }
+
 }

library/src/main/java/com/google/android/exoplayer/text/ttml/TtmlParser.java

@@ -73,8 +73,23 @@ public class TtmlParser implements SubtitleParser {
   private static final int DEFAULT_TICKRATE = 1;
 
   private final XmlPullParserFactory xmlParserFactory;
+  private final boolean strictParsing;
 
+  /**
+   * Equivalent to {@code TtmlParser(true)}.
+   */
   public TtmlParser() {
+    this(true);
+  }
+
+  /**
+   * @param strictParsing If true, {@link #parse(InputStream, String, long)} will throw a
+   *     {@link ParserException} if the stream contains invalid ttml. If false, the parser will
+   *     make a best effort to ignore minor errors in the stream. Note however that a
+   *     {@link ParserException} will still be thrown when this is not possible.
+   */
+  public TtmlParser(boolean strictParsing) {
+    this.strictParsing = strictParsing;
     try {
       xmlParserFactory = XmlPullParserFactory.newInstance();
     } catch (XmlPullParserException e) {
@@ -90,21 +105,31 @@ public class TtmlParser implements SubtitleParser {
       xmlParser.setInput(inputStream, inputEncoding);
       TtmlSubtitle ttmlSubtitle = null;
       LinkedList<TtmlNode> nodeStack = new LinkedList<TtmlNode>();
-      int unsupportedTagDepth = 0;
+      int unsupportedNodeDepth = 0;
       int eventType = xmlParser.getEventType();
       while (eventType != XmlPullParser.END_DOCUMENT) {
         TtmlNode parent = nodeStack.peekLast();
-        if (unsupportedTagDepth == 0) {
+        if (unsupportedNodeDepth == 0) {
           String name = xmlParser.getName();
           if (eventType == XmlPullParser.START_TAG) {
             if (!isSupportedTag(name)) {
-              Log.w(TAG, "Ignoring unsupported tag: " + xmlParser.getName());
-              unsupportedTagDepth++;
+              Log.i(TAG, "Ignoring unsupported tag: " + xmlParser.getName());
+              unsupportedNodeDepth++;
             } else {
-              TtmlNode node = parseNode(xmlParser, parent);
-              nodeStack.addLast(node);
-              if (parent != null) {
-                parent.addChild(node);
+              try {
+                TtmlNode node = parseNode(xmlParser, parent);
+                nodeStack.addLast(node);
+                if (parent != null) {
+                  parent.addChild(node);
+                }
+              } catch (ParserException e) {
+                if (strictParsing) {
+                  throw e;
+                } else {
+                  Log.e(TAG, "Suppressing parser error", e);
+                  // Treat the node (and by extension, all of its children) as unsupported.
+                  unsupportedNodeDepth++;
+                }
               }
             }
           } else if (eventType == XmlPullParser.TEXT) {
@@ -117,9 +142,9 @@ public class TtmlParser implements SubtitleParser {
           }
         } else {
           if (eventType == XmlPullParser.START_TAG) {
-            unsupportedTagDepth++;
+            unsupportedNodeDepth++;
           } else if (eventType == XmlPullParser.END_TAG) {
-            unsupportedTagDepth--;
+            unsupportedNodeDepth--;
           }
         }
         xmlParser.next();
@@ -127,7 +152,7 @@ public class TtmlParser implements SubtitleParser {
       }
       return ttmlSubtitle;
     } catch (XmlPullParserException xppe) {
-      throw new IOException("Unable to parse source", xppe);
+      throw new ParserException("Unable to parse source", xppe);
     }
   }