Ignore repeated control characters in EIA608 subtitles.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=117220536

library/src/main/java/com/google/android/exoplayer/text/eia608/ClosedCaptionCtrl.java

@@ -94,4 +94,8 @@ package com.google.android.exoplayer.text.eia608;
     return (cc1 >= 0x10 && cc1 <= 0x1F) && (cc2 >= 0x40 && cc2 <= 0x7F);
   }
 
+  public boolean isRepeatable() {
+    return cc1 >= 0x10 && cc1 <= 0x1F;
+  }
+
 }

library/src/main/java/com/google/android/exoplayer/text/eia608/Eia608TrackRenderer.java

@@ -66,6 +66,7 @@ public final class Eia608TrackRenderer extends SampleSourceTrackRenderer impleme
   private int captionRowCount;
   private String caption;
   private String lastRenderedCaption;
+  private ClosedCaptionCtrl repeatableControl;
 
   /**
    * @param textRenderer The text renderer.
@@ -94,6 +95,7 @@ public final class Eia608TrackRenderer extends SampleSourceTrackRenderer impleme
   @Override
   protected void onReset(long positionUs) {
     inputStreamEnded = false;
+    repeatableControl = null;
     pendingCaptionLists.clear();
     clearPendingSample();
     captionRowCount = DEFAULT_CAPTIONS_ROW_COUNT;
@@ -193,10 +195,20 @@ public final class Eia608TrackRenderer extends SampleSourceTrackRenderer impleme
       return;
     }
 
+    boolean isRepeatableControl = false;
     for (int i = 0; i < captionBufferSize; i++) {
       ClosedCaption caption = captionList.captions[i];
       if (caption.type == ClosedCaption.TYPE_CTRL) {
         ClosedCaptionCtrl captionCtrl = (ClosedCaptionCtrl) caption;
+        isRepeatableControl = captionBufferSize == 1 && captionCtrl.isRepeatable();
+        if (isRepeatableControl && repeatableControl != null
+            && repeatableControl.cc1 == captionCtrl.cc1
+            && repeatableControl.cc2 == captionCtrl.cc2) {
+          repeatableControl = null;
+          continue;
+        } else if (isRepeatableControl) {
+          repeatableControl = captionCtrl;
+        }
         if (captionCtrl.isMiscCode()) {
           handleMiscCode(captionCtrl);
         } else if (captionCtrl.isPreambleAddressCode()) {
@@ -207,6 +219,9 @@ public final class Eia608TrackRenderer extends SampleSourceTrackRenderer impleme
       }
     }
 
+    if (!isRepeatableControl) {
+      repeatableControl = null;
+    }
     if (captionMode == CC_MODE_ROLL_UP || captionMode == CC_MODE_PAINT_ON) {
       caption = getDisplayCaption();
     }