diff --git a/res/layout/captioning_preview.xml b/res/layout/captioning_preview.xml
index b90c3a5c296..92824d5606d 100644
--- a/res/layout/captioning_preview.xml
+++ b/res/layout/captioning_preview.xml
@@ -23,7 +23,9 @@
     <FrameLayout
         android:id="@+id/preview_viewport"
         android:layout_width="match_parent"
-        android:layout_height="@dimen/captioning_preview_height" >
+        android:layout_height="@dimen/captioning_preview_height"
+        android:paddingStart="@dimen/settings_side_margin"
+        android:paddingEnd="@dimen/settings_side_margin" >
 
         <ImageView
             android:layout_width="match_parent"
diff --git a/src/com/android/settings/accessibility/CaptionPropertiesFragment.java b/src/com/android/settings/accessibility/CaptionPropertiesFragment.java
index fa664bbbd3a..9822fc39d80 100644
--- a/src/com/android/settings/accessibility/CaptionPropertiesFragment.java
+++ b/src/com/android/settings/accessibility/CaptionPropertiesFragment.java
@@ -206,7 +206,10 @@ public class CaptionPropertiesFragment extends SettingsPreferenceFragment
         final ContentResolver cr = context.getContentResolver();
         final float fontScale = manager.getFontScale();
         if (previewWindow != null) {
-            previewText.setTextSize(previewWindow.getHeight() * LINE_HEIGHT_RATIO * fontScale);
+            // Assume the viewport is clipped with a 16:9 aspect ratio.
+            final float virtualHeight = Math.max(9 * previewWindow.getWidth(),
+                    16 * previewWindow.getHeight()) / 16.0f;
+            previewText.setTextSize(virtualHeight * LINE_HEIGHT_RATIO * fontScale);
         } else {
             final float textSize = context.getResources().getDimension(
                     R.dimen.caption_preview_text_size);