diff --git a/testdata/src/test/assets/media/ttml/chain_multiple_styles.xml b/testdata/src/test/assets/media/ttml/chain_multiple_styles.xml
index 307a44a507..c207091794 100644
--- a/testdata/src/test/assets/media/ttml/chain_multiple_styles.xml
+++ b/testdata/src/test/assets/media/ttml/chain_multiple_styles.xml
@@ -1,8 +1,7 @@
 <tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata"
     xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
     xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
-    xmlns="http://www.w3.org/ns/ttml"
-    xmlns="http://www.w3.org/2006/10/ttaf1">
+    xmlns="http://www.w3.org/ns/ttml">
   <head>
     <styling>
       <style id="s0"
diff --git a/testdata/src/test/assets/media/ttml/font_size.xml b/testdata/src/test/assets/media/ttml/font_size.xml
index 986931e547..dec801e1cc 100644
--- a/testdata/src/test/assets/media/ttml/font_size.xml
+++ b/testdata/src/test/assets/media/ttml/font_size.xml
@@ -1,8 +1,7 @@
 <tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata"
     xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
     xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
-    xmlns="http://www.w3.org/ns/ttml"
-    xmlns="http://www.w3.org/2006/10/ttaf1">
+    xmlns="http://www.w3.org/ns/ttml">
   <body>
     <div>
       <p begin="10s" end="18s" tts:fontSize="32px">text 1</p>
diff --git a/testdata/src/test/assets/media/ttml/font_size_empty.xml b/testdata/src/test/assets/media/ttml/font_size_empty.xml
index fdfc03ea6d..44f41c1e0a 100644
--- a/testdata/src/test/assets/media/ttml/font_size_empty.xml
+++ b/testdata/src/test/assets/media/ttml/font_size_empty.xml
@@ -1,7 +1,7 @@
-<tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata" xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
-  xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
-  xmlns="http://www.w3.org/ns/ttml"
-  xmlns="http://www.w3.org/2006/10/ttaf1">
+<tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata"
+    xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
+    xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
+    xmlns="http://www.w3.org/ns/ttml">
   <body>
     <div>
       <p begin="10s" end="18s" tts:fontSize="">empty</p>
diff --git a/testdata/src/test/assets/media/ttml/font_size_invalid.xml b/testdata/src/test/assets/media/ttml/font_size_invalid.xml
index 2635656445..6613286cf4 100644
--- a/testdata/src/test/assets/media/ttml/font_size_invalid.xml
+++ b/testdata/src/test/assets/media/ttml/font_size_invalid.xml
@@ -1,7 +1,7 @@
-<tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata" xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
-  xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
-  xmlns="http://www.w3.org/ns/ttml"
-  xmlns="http://www.w3.org/2006/10/ttaf1">
+<tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata"
+    xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
+    xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
+    xmlns="http://www.w3.org/ns/ttml">
   <body>
     <div>
       <p begin="10s" end="18s" tts:fontSize="px">invalid</p>
diff --git a/testdata/src/test/assets/media/ttml/font_size_no_unit.xml b/testdata/src/test/assets/media/ttml/font_size_no_unit.xml
index 126bd1ff33..98868b2881 100644
--- a/testdata/src/test/assets/media/ttml/font_size_no_unit.xml
+++ b/testdata/src/test/assets/media/ttml/font_size_no_unit.xml
@@ -1,7 +1,7 @@
-<tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata" xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
-  xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
-  xmlns="http://www.w3.org/ns/ttml"
-  xmlns="http://www.w3.org/2006/10/ttaf1">
+<tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata"
+    xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
+    xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
+    xmlns="http://www.w3.org/ns/ttml">
   <body>
     <div>
       <p begin="10s" end="18s" tts:fontSize="32">no unit</p>
diff --git a/testdata/src/test/assets/media/ttml/inherit_and_override_style.xml b/testdata/src/test/assets/media/ttml/inherit_and_override_style.xml
index 599e22ef1b..838c8b9822 100644
--- a/testdata/src/test/assets/media/ttml/inherit_and_override_style.xml
+++ b/testdata/src/test/assets/media/ttml/inherit_and_override_style.xml
@@ -1,5 +1,4 @@
 <tt xmlns="http://www.w3.org/ns/ttml"
-    xmlns="http://www.w3.org/2006/10/ttaf1"
     xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
     xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
     xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata">
diff --git a/testdata/src/test/assets/media/ttml/inherit_global_and_parent.xml b/testdata/src/test/assets/media/ttml/inherit_global_and_parent.xml
index 50ef19440d..e70d96f943 100644
--- a/testdata/src/test/assets/media/ttml/inherit_global_and_parent.xml
+++ b/testdata/src/test/assets/media/ttml/inherit_global_and_parent.xml
@@ -1,5 +1,4 @@
 <tt xmlns="http://www.w3.org/ns/ttml"
-    xmlns="http://www.w3.org/2006/10/ttaf1"
     xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
     xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
     xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata">
diff --git a/testdata/src/test/assets/media/ttml/inherit_multiple_styles.xml b/testdata/src/test/assets/media/ttml/inherit_multiple_styles.xml
index 19ce4defc2..9b8354e33e 100644
--- a/testdata/src/test/assets/media/ttml/inherit_multiple_styles.xml
+++ b/testdata/src/test/assets/media/ttml/inherit_multiple_styles.xml
@@ -1,8 +1,7 @@
 <tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata"
     xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
     xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
-    xmlns="http://www.w3.org/ns/ttml"
-    xmlns="http://www.w3.org/2006/10/ttaf1">
+    xmlns="http://www.w3.org/ns/ttml">
   <head>
     <styling>
       <style id="s0"
diff --git a/testdata/src/test/assets/media/ttml/inherit_style.xml b/testdata/src/test/assets/media/ttml/inherit_style.xml
index 808087960c..ec17781737 100644
--- a/testdata/src/test/assets/media/ttml/inherit_style.xml
+++ b/testdata/src/test/assets/media/ttml/inherit_style.xml
@@ -1,5 +1,4 @@
 <tt xmlns="http://www.w3.org/ns/ttml"
-    xmlns="http://www.w3.org/2006/10/ttaf1"
     xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
     xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
     xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata">
diff --git a/testdata/src/test/assets/media/ttml/inline_style_attributes.xml b/testdata/src/test/assets/media/ttml/inline_style_attributes.xml
index 3d7f4a7d77..3f3d21b1d0 100644
--- a/testdata/src/test/assets/media/ttml/inline_style_attributes.xml
+++ b/testdata/src/test/assets/media/ttml/inline_style_attributes.xml
@@ -1,5 +1,4 @@
 <tt xmlns="http://www.w3.org/ns/ttml"
-    xmlns="http://www.w3.org/2006/10/ttaf1"
     xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
     xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
     xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata">
diff --git a/testdata/src/test/assets/media/ttml/multiple_regions.xml b/testdata/src/test/assets/media/ttml/multiple_regions.xml
index 9404cd47d1..ab73eb7c72 100644
--- a/testdata/src/test/assets/media/ttml/multiple_regions.xml
+++ b/testdata/src/test/assets/media/ttml/multiple_regions.xml
@@ -1,5 +1,4 @@
 <tt xmlns="http://www.w3.org/ns/ttml"
-    xmlns="http://www.w3.org/2006/10/ttaf1"
     xmlns:id="http://www.w3.org/XML/1998/namespace"
     xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
     xmlns:tts="http://www.w3.org/ns/ttml#styling"
diff --git a/testdata/src/test/assets/media/ttml/no_underline_linethrough.xml b/testdata/src/test/assets/media/ttml/no_underline_linethrough.xml
index d7092a9415..13ea4e44ce 100644
--- a/testdata/src/test/assets/media/ttml/no_underline_linethrough.xml
+++ b/testdata/src/test/assets/media/ttml/no_underline_linethrough.xml
@@ -1,7 +1,7 @@
-<tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata" xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
-  xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
-  xmlns="http://www.w3.org/ns/ttml"
-  xmlns="http://www.w3.org/2006/10/ttaf1">
+<tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata"
+    xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
+    xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
+    xmlns="http://www.w3.org/ns/ttml">
   <head>
     <styling>
       <style id="s0"
diff --git a/testdata/src/test/assets/media/ttml/rubies.xml b/testdata/src/test/assets/media/ttml/rubies.xml
index 874dfebdc3..e149f16dfd 100644
--- a/testdata/src/test/assets/media/ttml/rubies.xml
+++ b/testdata/src/test/assets/media/ttml/rubies.xml
@@ -1,23 +1,7 @@
-<!--
-  ~ Copyright (C) 2020 The Android Open Source Project
-  ~
-  ~ Licensed under the Apache License, Version 2.0 (the "License");
-  ~ you may not use this file except in compliance with the License.
-  ~ You may obtain a copy of the License at
-  ~
-  ~      http://www.apache.org/licenses/LICENSE-2.0
-  ~
-  ~ Unless required by applicable law or agreed to in writing, software
-  ~ distributed under the License is distributed on an "AS IS" BASIS,
-  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  ~ See the License for the specific language governing permissions and
-  ~ limitations under the License.
-  ~
-  -->
 <tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata"
-  xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
-  xmlns:tts="http://www.w3.org/2006/10/ttaf1#style" xmlns="http://www.w3.org/ns/ttml"
-  xmlns="http://www.w3.org/2006/10/ttaf1">
+    xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
+    xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
+    xmlns="http://www.w3.org/ns/ttml">
   <head>
     <styling>
       <style id="cont" tts:ruby="container" />
diff --git a/testdata/src/test/assets/media/ttml/text_align.xml b/testdata/src/test/assets/media/ttml/text_align.xml
index fbc596874e..7244a7c292 100644
--- a/testdata/src/test/assets/media/ttml/text_align.xml
+++ b/testdata/src/test/assets/media/ttml/text_align.xml
@@ -1,8 +1,7 @@
 <tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata"
     xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
     xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
-    xmlns="http://www.w3.org/ns/ttml"
-    xmlns="http://www.w3.org/2006/10/ttaf1">
+    xmlns="http://www.w3.org/ns/ttml">
   <body>
     <div>
       <p begin="10s" end="18s" tts:textAlign="start">Start alignment</p>
diff --git a/testdata/src/test/assets/media/ttml/text_combine.xml b/testdata/src/test/assets/media/ttml/text_combine.xml
index 41260581dd..dcba3913ca 100644
--- a/testdata/src/test/assets/media/ttml/text_combine.xml
+++ b/testdata/src/test/assets/media/ttml/text_combine.xml
@@ -1,24 +1,8 @@
-<!--
-  ~ Copyright (C) 2020 The Android Open Source Project
-  ~
-  ~ Licensed under the Apache License, Version 2.0 (the "License");
-  ~ you may not use this file except in compliance with the License.
-  ~ You may obtain a copy of the License at
-  ~
-  ~      http://www.apache.org/licenses/LICENSE-2.0
-  ~
-  ~ Unless required by applicable law or agreed to in writing, software
-  ~ distributed under the License is distributed on an "AS IS" BASIS,
-  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-  ~ See the License for the specific language governing permissions and
-  ~ limitations under the License.
-  ~
-  -->
 <tt xmlns:ttm="http://www.w3.org/2006/10/ttaf1#metadata"
   xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
   xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
   xmlns="http://www.w3.org/ns/ttml"
-  xmlns="http://www.w3.org/2006/10/ttaf1">
+  >
   <body>
     <div>
       <p begin="10s" end="18s">Text with <span tts:textCombine="all">combined</span> section.</p>
diff --git a/testdata/src/test/assets/media/ttml/vertical_text.xml b/testdata/src/test/assets/media/ttml/vertical_text.xml
index 49bbb3caab..cd306aba91 100644
--- a/testdata/src/test/assets/media/ttml/vertical_text.xml
+++ b/testdata/src/test/assets/media/ttml/vertical_text.xml
@@ -2,7 +2,7 @@
     xmlns:ttp="http://www.w3.org/2006/10/ttaf1#parameter"
     xmlns:tts="http://www.w3.org/2006/10/ttaf1#style"
     xmlns="http://www.w3.org/ns/ttml"
-    xmlns="http://www.w3.org/2006/10/ttaf1">
+    >
   <head>
     <layout>
       <region id="right-to-left" tts:extent="80% 80%" tts:origin="10% 10%" tts:writingMode="tbrl" />
