diff --git a/.buildinfo b/.buildinfo
index a640ed6..da7b1df 100644
--- a/.buildinfo
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diff --git a/_static/documentation_options.js b/_static/documentation_options.js
index d7cfb0d..ce89a2d 100644
--- a/_static/documentation_options.js
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@@ -1,6 +1,6 @@
 var DOCUMENTATION_OPTIONS = {
     URL_ROOT: document.getElementById("documentation_options").getAttribute('data-url_root'),
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+    VERSION: '1.21',
     LANGUAGE: 'en',
     COLLAPSE_INDEX: false,
     BUILDER: 'html',
diff --git a/genindex.html b/genindex.html
index 99a75dd..269c362 100644
--- a/genindex.html
+++ b/genindex.html
@@ -3,7 +3,7 @@
 <head>
   <meta charset="utf-8" />
   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-  <title>Index &mdash; kaldifeat 1.20 documentation</title>
+  <title>Index &mdash; kaldifeat 1.21 documentation</title>
       <link rel="stylesheet" href="_static/pygments.css" type="text/css" />
       <link rel="stylesheet" href="_static/css/theme.css" type="text/css" />
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+                1.21
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diff --git a/index.html b/index.html
index 960307c..8a80245 100644
--- a/index.html
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@@ -4,7 +4,7 @@
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   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-  <title>kaldifeat &mdash; kaldifeat 1.20 documentation</title>
+  <title>kaldifeat &mdash; kaldifeat 1.21 documentation</title>
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index 882df22..d4885c8 100644
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@@ -4,7 +4,7 @@
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   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-  <title>Installation &mdash; kaldifeat 1.20 documentation</title>
+  <title>Installation &mdash; kaldifeat 1.21 documentation</title>
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diff --git a/intro.html b/intro.html
index d741d37..78cc662 100644
--- a/intro.html
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@@ -4,7 +4,7 @@
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   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-  <title>Introduction &mdash; kaldifeat 1.20 documentation</title>
+  <title>Introduction &mdash; kaldifeat 1.21 documentation</title>
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@@ -32,7 +32,7 @@
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+                1.21
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diff --git a/objects.inv b/objects.inv
index 831966b..9131045 100644
--- a/objects.inv
+++ b/objects.inv
@@ -1,5 +1,5 @@
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index dcb8bae..2374bcc 100644
--- a/search.html
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@@ -3,7 +3,7 @@
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   <meta charset="utf-8" />
   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-  <title>Search &mdash; kaldifeat 1.20 documentation</title>
+  <title>Search &mdash; kaldifeat 1.21 documentation</title>
       <link rel="stylesheet" href="_static/pygments.css" type="text/css" />
       <link rel="stylesheet" href="_static/css/theme.css" type="text/css" />
     
@@ -32,7 +32,7 @@
             <a href="index.html" class="icon icon-home"> kaldifeat
           </a>
               <div class="version">
-                1.20
+                1.21
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   <form id="rtd-search-form" class="wy-form" action="#" method="get">
diff --git a/usage/fbank.html b/usage/fbank.html
index 95a9c99..a10f89b 100644
--- a/usage/fbank.html
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@@ -4,7 +4,7 @@
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   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-  <title>kaldifeat.Fbank &mdash; kaldifeat 1.20 documentation</title>
+  <title>kaldifeat.Fbank &mdash; kaldifeat 1.21 documentation</title>
       <link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
       <link rel="stylesheet" href="../_static/css/theme.css" type="text/css" />
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@@ -32,7 +32,7 @@
             <a href="../index.html" class="icon icon-home"> kaldifeat
           </a>
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diff --git a/usage/fbank_options.html b/usage/fbank_options.html
index 62a34fb..b566a7d 100644
--- a/usage/fbank_options.html
+++ b/usage/fbank_options.html
@@ -4,7 +4,7 @@
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   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-  <title>kaldifeat.FbankOptions &mdash; kaldifeat 1.20 documentation</title>
+  <title>kaldifeat.FbankOptions &mdash; kaldifeat 1.21 documentation</title>
       <link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
       <link rel="stylesheet" href="../_static/css/theme.css" type="text/css" />
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@@ -32,7 +32,7 @@
             <a href="../index.html" class="icon icon-home"> kaldifeat
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-                1.20
+                1.21
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diff --git a/usage/index.html b/usage/index.html
index 80c1c24..ff1add5 100644
--- a/usage/index.html
+++ b/usage/index.html
@@ -4,7 +4,7 @@
   <meta charset="utf-8" /><meta name="generator" content="Docutils 0.17.1: http://docutils.sourceforge.net/" />
 
   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-  <title>Usage &mdash; kaldifeat 1.20 documentation</title>
+  <title>Usage &mdash; kaldifeat 1.21 documentation</title>
       <link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
       <link rel="stylesheet" href="../_static/css/theme.css" type="text/css" />
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@@ -32,7 +32,7 @@
             <a href="../index.html" class="icon icon-home"> kaldifeat
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+                1.21
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   <form id="rtd-search-form" class="wy-form" action="../search.html" method="get">
diff --git a/usage/online_fbank.html b/usage/online_fbank.html
index ae53049..8dd3b44 100644
--- a/usage/online_fbank.html
+++ b/usage/online_fbank.html
@@ -4,7 +4,7 @@
   <meta charset="utf-8" /><meta name="generator" content="Docutils 0.17.1: http://docutils.sourceforge.net/" />
 
   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
-  <title>kaldifeat.OnlineFbank &mdash; kaldifeat 1.20 documentation</title>
+  <title>kaldifeat.OnlineFbank &mdash; kaldifeat 1.21 documentation</title>
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