tutorials/speech_recognition/ctc.html - mxnet-site - Git at Google

 <!DOCTYPE html>

 <html lang="en">
 <head>
 <meta charset="utf-8"/>
 <meta content="IE=edge" http-equiv="X-UA-Compatible"/>
 <meta content="width=device-width, initial-scale=1" name="viewport"/>
 <title>Connectionist Temporal Classification — mxnet  documentation</title>
 <link crossorigin="anonymous" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" integrity="sha384-1q8mTJOASx8j1Au+a5WDVnPi2lkFfwwEAa8hDDdjZlpLegxhjVME1fgjWPGmkzs7" rel="stylesheet"/>
 <link href="https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css" rel="stylesheet"/>
 <link href="../../_static/basic.css" rel="stylesheet" type="text/css">
 <link href="../../_static/pygments.css" rel="stylesheet" type="text/css">
 <link href="../../_static/mxnet.css" rel="stylesheet" type="text/css"/>
 <script type="text/javascript">
       var DOCUMENTATION_OPTIONS = {
         URL_ROOT:    '../../',
         VERSION:     '',
         COLLAPSE_INDEX: false,
         FILE_SUFFIX: '.html',
         HAS_SOURCE:  true,
         SOURCELINK_SUFFIX: ''
       };
     </script>
 <script src="https://code.jquery.com/jquery-1.11.1.min.js" type="text/javascript"></script>
 <script src="../../_static/underscore.js" type="text/javascript"></script>
 <script src="../../_static/searchtools_custom.js" type="text/javascript"></script>
 <script src="../../_static/doctools.js" type="text/javascript"></script>
 <script src="../../_static/selectlang.js" type="text/javascript"></script>
 <script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML" type="text/javascript"></script>
 <script type="text/javascript"> jQuery(function() { Search.loadIndex("/searchindex.js"); Search.init();}); </script>
 <script>
       (function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
       (i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new
       Date();a=s.createElement(o),
       m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
       })(window,document,'script','https://www.google-analytics.com/analytics.js','ga');

       ga('create', 'UA-96378503-1', 'auto');
       ga('send', 'pageview');

     </script>
 <!-- -->
 <!-- <script type="text/javascript" src="../../_static/jquery.js"></script> -->
 <!-- -->
 <!-- <script type="text/javascript" src="../../_static/underscore.js"></script> -->
 <!-- -->
 <!-- <script type="text/javascript" src="../../_static/doctools.js"></script> -->
 <!-- -->
 <!-- <script type="text/javascript" src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script> -->
 <!-- -->
 <link href="https://raw.githubusercontent.com/dmlc/web-data/master/mxnet/image/mxnet-icon.png" rel="icon" type="image/png"/>
 </link></link></head>
 <body background="https://raw.githubusercontent.com/dmlc/web-data/master/mxnet/image/mxnet-background-compressed.jpeg" role="document">
 <div class="content-block"><div class="navbar navbar-fixed-top">
 <div class="container" id="navContainer">
 <div class="innder" id="header-inner">
 <h1 id="logo-wrap">
 <a href="../../" id="logo"><img src="https://raw.githubusercontent.com/dmlc/web-data/master/mxnet/image/mxnet_logo.png"/></a>
 </h1>
 <nav class="nav-bar" id="main-nav">
 <a class="main-nav-link" href="../../install/index.html">Install</a>
 <span id="dropdown-menu-position-anchor">
 <a aria-expanded="true" aria-haspopup="true" class="main-nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button">Gluon <span class="caret"></span></a>
 <ul class="dropdown-menu navbar-menu" id="package-dropdown-menu">
 <li><a class="main-nav-link" href="../../gluon/index.html">About</a></li>
 <li><a class="main-nav-link" href="http://gluon.mxnet.io">Tutorials</a></li>
 </ul>
 </span>
 <span id="dropdown-menu-position-anchor">
 <a aria-expanded="true" aria-haspopup="true" class="main-nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button">API <span class="caret"></span></a>
 <ul class="dropdown-menu navbar-menu" id="package-dropdown-menu">
 <li><a class="main-nav-link" href="../../api/python/index.html">Python</a></li>
 <li><a class="main-nav-link" href="../../api/scala/index.html">Scala</a></li>
 <li><a class="main-nav-link" href="../../api/r/index.html">R</a></li>
 <li><a class="main-nav-link" href="../../api/julia/index.html">Julia</a></li>
 <li><a class="main-nav-link" href="../../api/c++/index.html">C++</a></li>
 <li><a class="main-nav-link" href="../../api/perl/index.html">Perl</a></li>
 </ul>
 </span>
 <span id="dropdown-menu-position-anchor-docs">
 <a aria-expanded="true" aria-haspopup="true" class="main-nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button">Docs <span class="caret"></span></a>
 <ul class="dropdown-menu navbar-menu" id="package-dropdown-menu-docs">
 <li><a class="main-nav-link" href="../../tutorials/index.html">Tutorials</a>
 <li><a class="main-nav-link" href="../../faq/index.html">FAQ</a></li>
 <li><a class="main-nav-link" href="../../architecture/index.html">Architecture</a></li>
 <li><a class="main-nav-link" href="https://github.com/apache/incubator-mxnet/tree/1.1.0/example">Examples</a></li>
 <li><a class="main-nav-link" href="../../api/python/gluon/model_zoo.html">Gluon Model Zoo</a></li>
 </li></ul>
 </span>
 <a class="main-nav-link" href="https://github.com/dmlc/mxnet">Github</a>
 <span id="dropdown-menu-position-anchor-community">
 <a aria-expanded="true" aria-haspopup="true" class="main-nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button">Community <span class="caret"></span></a>
 <ul class="dropdown-menu navbar-menu" id="package-dropdown-menu-community">
 <li><a class="main-nav-link" href="../../community/index.html">Community</a></li>
 <li><a class="main-nav-link" href="../../community/contribute.html">Contribute</a></li>
 <li><a class="main-nav-link" href="../../community/powered_by.html">Powered By</a></li>
 <li><a class="main-nav-link" href="http://discuss.mxnet.io">Discuss</a></li>
 </ul>
 </span>
 <span id="dropdown-menu-position-anchor-version" style="position: relative"><a href="#" class="main-nav-link dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="true">Versions(1.1.0)<span class="caret"></span></a><ul id="package-dropdown-menu" class="dropdown-menu"><li><a class="main-nav-link" href=https://mxnet.incubator.apache.org/>1.1.0</a></li><li><a class="main-nav-link" href=https://mxnet.incubator.apache.org/versions/1.0.0/index.html>1.0.0</a></li><li><a class="main-nav-link" href=https://mxnet.incubator.apache.org/versions/0.12.1/index.html>0.12.1</a></li><li><a class="main-nav-link" href=https://mxnet.incubator.apache.org/versions/0.12.0/index.html>0.12.0</a></li><li><a class="main-nav-link" href=https://mxnet.incubator.apache.org/versions/0.11.0/index.html>0.11.0</a></li><li><a class="main-nav-link" href=https://mxnet.incubator.apache.org/versions/master/index.html>master</a></li></ul></span></nav>
 <script> function getRootPath(){ return "../../" } </script>
 <div class="burgerIcon dropdown">
 <a class="dropdown-toggle" data-toggle="dropdown" href="#" role="button">☰</a>
 <ul class="dropdown-menu" id="burgerMenu">
 <li><a href="../../install/index.html">Install</a></li>
 <li><a class="main-nav-link" href="../../tutorials/index.html">Tutorials</a></li>
 <li class="dropdown-submenu">
 <a href="#" tabindex="-1">Community</a>
 <ul class="dropdown-menu">
 <li><a href="../../community/index.html" tabindex="-1">Community</a></li>
 <li><a href="../../community/contribute.html" tabindex="-1">Contribute</a></li>
 <li><a href="../../community/powered_by.html" tabindex="-1">Powered By</a></li>
 </ul>
 </li>
 <li class="dropdown-submenu">
 <a href="#" tabindex="-1">API</a>
 <ul class="dropdown-menu">
 <li><a href="../../api/python/index.html" tabindex="-1">Python</a>
 </li>
 <li><a href="../../api/scala/index.html" tabindex="-1">Scala</a>
 </li>
 <li><a href="../../api/r/index.html" tabindex="-1">R</a>
 </li>
 <li><a href="../../api/julia/index.html" tabindex="-1">Julia</a>
 </li>
 <li><a href="../../api/c++/index.html" tabindex="-1">C++</a>
 </li>
 <li><a href="../../api/perl/index.html" tabindex="-1">Perl</a>
 </li>
 </ul>
 </li>
 <li class="dropdown-submenu">
 <a href="#" tabindex="-1">Docs</a>
 <ul class="dropdown-menu">
 <li><a href="../../tutorials/index.html" tabindex="-1">Tutorials</a></li>
 <li><a href="../../faq/index.html" tabindex="-1">FAQ</a></li>
 <li><a href="../../architecture/index.html" tabindex="-1">Architecture</a></li>
 <li><a href="https://github.com/apache/incubator-mxnet/tree/1.1.0/example" tabindex="-1">Examples</a></li>
 <li><a href="../../api/python/gluon/model_zoo.html" tabindex="-1">Gluon Model Zoo</a></li>
 </ul>
 </li>
 <li><a href="../../architecture/index.html">Architecture</a></li>
 <li><a class="main-nav-link" href="https://github.com/dmlc/mxnet">Github</a></li>
 <li id="dropdown-menu-position-anchor-version-mobile" class="dropdown-submenu" style="position: relative"><a href="#" tabindex="-1">Versions(1.1.0)</a><ul class="dropdown-menu"><li><a tabindex="-1" href=https://mxnet.incubator.apache.org/>1.1.0</a></li><li><a tabindex="-1" href=https://mxnet.incubator.apache.org/versions/1.0.0/index.html>1.0.0</a></li><li><a tabindex="-1" href=https://mxnet.incubator.apache.org/versions/0.12.1/index.html>0.12.1</a></li><li><a tabindex="-1" href=https://mxnet.incubator.apache.org/versions/0.12.0/index.html>0.12.0</a></li><li><a tabindex="-1" href=https://mxnet.incubator.apache.org/versions/0.11.0/index.html>0.11.0</a></li><li><a tabindex="-1" href=https://mxnet.incubator.apache.org/versions/master/index.html>master</a></li></ul></li></ul>
 </div>
 <div class="plusIcon dropdown">
 <a class="dropdown-toggle" data-toggle="dropdown" href="#" role="button"><span aria-hidden="true" class="glyphicon glyphicon-plus"></span></a>
 <ul class="dropdown-menu dropdown-menu-right" id="plusMenu"></ul>
 </div>
 <div id="search-input-wrap">
 <form action="../../search.html" autocomplete="off" class="" method="get" role="search">
 <div class="form-group inner-addon left-addon">
 <i class="glyphicon glyphicon-search"></i>
 <input class="form-control" name="q" placeholder="Search" type="text"/>
 </div>
 <input name="check_keywords" type="hidden" value="yes">
 <input name="area" type="hidden" value="default"/>
 </input></form>
 <div id="search-preview"></div>
 </div>
 <div id="searchIcon">
 <span aria-hidden="true" class="glyphicon glyphicon-search"></span>
 </div>
 <!-- <div id="lang-select-wrap"> -->
 <!--   <label id="lang-select-label"> -->
 <!--     <\!-- <i class="fa fa-globe"></i> -\-> -->
 <!--     <span></span> -->
 <!--   </label> -->
 <!--   <select id="lang-select"> -->
 <!--     <option value="en">Eng</option> -->
 <!--     <option value="zh">中文</option> -->
 <!--   </select> -->
 <!-- </div> -->
 <!--     <a id="mobile-nav-toggle">
         <span class="mobile-nav-toggle-bar"></span>
         <span class="mobile-nav-toggle-bar"></span>
         <span class="mobile-nav-toggle-bar"></span>
       </a> -->
 </div>
 </div>
 </div>
 <script type="text/javascript">
         $('body').css('background', 'white');
     </script>
 <div class="container">
 <div class="row">
 <div aria-label="main navigation" class="sphinxsidebar leftsidebar" role="navigation">
 <div class="sphinxsidebarwrapper">
 <ul>
 <li class="toctree-l1"><a class="reference internal" href="../../api/python/index.html">Python Documents</a></li>
 <li class="toctree-l1"><a class="reference internal" href="../../api/r/index.html">R Documents</a></li>
 <li class="toctree-l1"><a class="reference internal" href="../../api/julia/index.html">Julia Documents</a></li>
 <li class="toctree-l1"><a class="reference internal" href="../../api/c++/index.html">C++ Documents</a></li>
 <li class="toctree-l1"><a class="reference internal" href="../../api/scala/index.html">Scala Documents</a></li>
 <li class="toctree-l1"><a class="reference internal" href="../../api/perl/index.html">Perl Documents</a></li>
 <li class="toctree-l1"><a class="reference internal" href="../../faq/index.html">HowTo Documents</a></li>
 <li class="toctree-l1"><a class="reference internal" href="../../architecture/index.html">System Documents</a></li>
 <li class="toctree-l1"><a class="reference internal" href="../index.html">Tutorials</a></li>
 <li class="toctree-l1"><a class="reference internal" href="../../community/index.html">Community</a></li>
 </ul>
 </div>
 </div>
 <div class="content">
 <div class="page-tracker"></div>
 <div class="section" id="connectionist-temporal-classification">
 <span id="connectionist-temporal-classification"></span><h1>Connectionist Temporal Classification<a class="headerlink" href="#connectionist-temporal-classification" title="Permalink to this headline">¶</a></h1>
 <p><a class="reference external" href="https://www.cs.toronto.edu/~graves/icml_2006.pdf">Connectionist Temporal Classification</a> (CTC) is a cost function that is used to train Recurrent Neural Networks (RNNs) to label unsegmented input sequence data in supervised learning. For example, in a speech recognition application, using a typical cross-entropy loss, the input signal needs to be segmented into words or sub-words. However, using CTC-loss, it suffices to provide one label sequence for input sequence and the network learns both the alignment as well labeling. Baidu’s warp-ctc page contains a more detailed <a class="reference external" href="https://github.com/baidu-research/warp-ctc#introduction">introduction to CTC-loss</a>.</p>
 <div class="section" id="ctc-loss-in-mxnet">
 <span id="ctc-loss-in-mxnet"></span><h2>CTC-loss in MXNet<a class="headerlink" href="#ctc-loss-in-mxnet" title="Permalink to this headline">¶</a></h2>
 <p>MXNet supports two CTC-loss layers in Symbol API:</p>
 <ul class="simple">
 <li><code class="docutils literal"><span class="pre">mxnet.symbol.contrib.ctc_loss</span></code> is implemented in MXNet and included as part of the standard package.</li>
 <li><code class="docutils literal"><span class="pre">mxnet.symbol.WarpCTC</span></code> uses Baidu’s warp-ctc library and requires building warp-ctc library and mxnet library both from source.</li>
 </ul>
 </div>
 <div class="section" id="lstm-ocr-example">
 <span id="lstm-ocr-example"></span><h2>LSTM OCR Example<a class="headerlink" href="#lstm-ocr-example" title="Permalink to this headline">¶</a></h2>
 <p>MXNet’s example folder contains a <a class="reference external" href="https://github.com/apache/incubator-mxnet/tree/1.1.0/example/ctc">CTC example</a> for using CTC loss with an LSTM network to perform Optical Character Recognition (OCR) prediction on CAPTCHA images. The example demonstrates use of both CTC loss options, as well as inference after training using network symbol and parameter checkpoints.</p>
 </div>
 <div class="section" id="next-steps">
 <span id="next-steps"></span><h2>Next Steps<a class="headerlink" href="#next-steps" title="Permalink to this headline">¶</a></h2>
 <div class="toctree-wrapper compound">
 <ul>
 <li class="toctree-l1"><a class="reference external" href="https://mxnet.incubator.apache.org/tutorials/index.html">MXNet tutorials index</a></li>
 </ul>
 </div>
 </div>
 </div>
 </div>
 </div>
 <div aria-label="main navigation" class="sphinxsidebar rightsidebar" role="navigation">
 <div class="sphinxsidebarwrapper">
 <h3><a href="../../index.html">Table Of Contents</a></h3>
 <ul>
 <li><a class="reference internal" href="#">Connectionist Temporal Classification</a><ul>
 <li><a class="reference internal" href="#ctc-loss-in-mxnet">CTC-loss in MXNet</a></li>
 <li><a class="reference internal" href="#lstm-ocr-example">LSTM OCR Example</a></li>
 <li><a class="reference internal" href="#next-steps">Next Steps</a></li>
 </ul>
 </li>
 </ul>
 </div>
 </div>
 </div><div class="footer">
 <div class="section-disclaimer">
 <div class="container">
 <div>
 <img height="60" src="https://raw.githubusercontent.com/dmlc/web-data/master/mxnet/image/apache_incubator_logo.png"/>
 <p>
             Apache MXNet is an effort undergoing incubation at The Apache Software Foundation (ASF), <strong>sponsored by the <i>Apache Incubator</i></strong>. Incubation is required of all newly accepted projects until a further review indicates that the infrastructure, communications, and decision making process have stabilized in a manner consistent with other successful ASF projects. While incubation status is not necessarily a reflection of the completeness or stability of the code, it does indicate that the project has yet to be fully endorsed by the ASF.
         </p>
 <p>
             "Copyright © 2017-2018, The Apache Software Foundation
             Apache MXNet, MXNet, Apache, the Apache feather, and the Apache MXNet project logo are either registered trademarks or trademarks of the Apache Software Foundation."
         </p>
 </div>
 </div>
 </div>
 </div> <!-- pagename != index -->
 </div>
 <script crossorigin="anonymous" integrity="sha384-0mSbJDEHialfmuBBQP6A4Qrprq5OVfW37PRR3j5ELqxss1yVqOtnepnHVP9aJ7xS" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
 <script src="../../_static/js/sidebar.js" type="text/javascript"></script>
 <script src="../../_static/js/search.js" type="text/javascript"></script>
 <script src="../../_static/js/navbar.js" type="text/javascript"></script>
 <script src="../../_static/js/clipboard.min.js" type="text/javascript"></script>
 <script src="../../_static/js/copycode.js" type="text/javascript"></script>
 <script src="../../_static/js/page.js" type="text/javascript"></script>
 <script type="text/javascript">
         $('body').ready(function () {
             $('body').css('visibility', 'visible');
         });
     </script>
 </body>
 </html>
	<!DOCTYPE html>

	<html lang="en">
	<head>
	<meta charset="utf-8"/>
	<meta content="IE=edge" http-equiv="X-UA-Compatible"/>
	<meta content="width=device-width, initial-scale=1" name="viewport"/>
	<title>Connectionist Temporal Classification — mxnet documentation</title>
	<link crossorigin="anonymous" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" integrity="sha384-1q8mTJOASx8j1Au+a5WDVnPi2lkFfwwEAa8hDDdjZlpLegxhjVME1fgjWPGmkzs7" rel="stylesheet"/>
	<link href="https://maxcdn.bootstrapcdn.com/font-awesome/4.5.0/css/font-awesome.min.css" rel="stylesheet"/>
	<link href="../../_static/basic.css" rel="stylesheet" type="text/css">
	<link href="../../_static/pygments.css" rel="stylesheet" type="text/css">
	<link href="../../_static/mxnet.css" rel="stylesheet" type="text/css"/>
	<script type="text/javascript">
	var DOCUMENTATION_OPTIONS = {
	URL_ROOT: '../../',
	VERSION: '',
	COLLAPSE_INDEX: false,
	FILE_SUFFIX: '.html',
	HAS_SOURCE: true,
	SOURCELINK_SUFFIX: ''
	};
	</script>
	<script src="https://code.jquery.com/jquery-1.11.1.min.js" type="text/javascript"></script>
	<script src="../../_static/underscore.js" type="text/javascript"></script>
	<script src="../../_static/searchtools_custom.js" type="text/javascript"></script>
	<script src="../../_static/doctools.js" type="text/javascript"></script>
	<script src="../../_static/selectlang.js" type="text/javascript"></script>
	<script src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML" type="text/javascript"></script>
	<script type="text/javascript"> jQuery(function() { Search.loadIndex("/searchindex.js"); Search.init();}); </script>
	<script>
	(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]\|\|function(){
	(i[r].q=i[r].q\|\|[]).push(arguments)},i[r].l=1*new
	Date();a=s.createElement(o),
	m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
	})(window,document,'script','https://www.google-analytics.com/analytics.js','ga');

	ga('create', 'UA-96378503-1', 'auto');
	ga('send', 'pageview');

	</script>
	<!-- -->
	<!-- <script type="text/javascript" src="../../_static/jquery.js"></script> -->
	<!-- -->
	<!-- <script type="text/javascript" src="../../_static/underscore.js"></script> -->
	<!-- -->
	<!-- <script type="text/javascript" src="../../_static/doctools.js"></script> -->
	<!-- -->
	<!-- <script type="text/javascript" src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script> -->
	<!-- -->
	<link href="https://raw.githubusercontent.com/dmlc/web-data/master/mxnet/image/mxnet-icon.png" rel="icon" type="image/png"/>
	</link></link></head>
	<body background="https://raw.githubusercontent.com/dmlc/web-data/master/mxnet/image/mxnet-background-compressed.jpeg" role="document">
	<div class="content-block"><div class="navbar navbar-fixed-top">
	<div class="container" id="navContainer">
	<div class="innder" id="header-inner">
	<h1 id="logo-wrap">
	<a href="../../" id="logo"><img src="https://raw.githubusercontent.com/dmlc/web-data/master/mxnet/image/mxnet_logo.png"/></a>
	</h1>
	<nav class="nav-bar" id="main-nav">
	<a class="main-nav-link" href="../../install/index.html">Install</a>
	<span id="dropdown-menu-position-anchor">
	<a aria-expanded="true" aria-haspopup="true" class="main-nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button">Gluon <span class="caret"></span></a>
	<ul class="dropdown-menu navbar-menu" id="package-dropdown-menu">
	<li><a class="main-nav-link" href="../../gluon/index.html">About</a></li>
	<li><a class="main-nav-link" href="http://gluon.mxnet.io">Tutorials</a></li>
	</ul>
	</span>
	<span id="dropdown-menu-position-anchor">
	<a aria-expanded="true" aria-haspopup="true" class="main-nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button">API <span class="caret"></span></a>
	<ul class="dropdown-menu navbar-menu" id="package-dropdown-menu">
	<li><a class="main-nav-link" href="../../api/python/index.html">Python</a></li>
	<li><a class="main-nav-link" href="../../api/scala/index.html">Scala</a></li>
	<li><a class="main-nav-link" href="../../api/r/index.html">R</a></li>
	<li><a class="main-nav-link" href="../../api/julia/index.html">Julia</a></li>
	<li><a class="main-nav-link" href="../../api/c++/index.html">C++</a></li>
	<li><a class="main-nav-link" href="../../api/perl/index.html">Perl</a></li>
	</ul>
	</span>
	<span id="dropdown-menu-position-anchor-docs">
	<a aria-expanded="true" aria-haspopup="true" class="main-nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button">Docs <span class="caret"></span></a>
	<ul class="dropdown-menu navbar-menu" id="package-dropdown-menu-docs">
	<li><a class="main-nav-link" href="../../tutorials/index.html">Tutorials</a>
	<li><a class="main-nav-link" href="../../faq/index.html">FAQ</a></li>
	<li><a class="main-nav-link" href="../../architecture/index.html">Architecture</a></li>
	<li><a class="main-nav-link" href="https://github.com/apache/incubator-mxnet/tree/1.1.0/example">Examples</a></li>
	<li><a class="main-nav-link" href="../../api/python/gluon/model_zoo.html">Gluon Model Zoo</a></li>
	</li></ul>
	</span>
	<a class="main-nav-link" href="https://github.com/dmlc/mxnet">Github</a>
	<span id="dropdown-menu-position-anchor-community">
	<a aria-expanded="true" aria-haspopup="true" class="main-nav-link dropdown-toggle" data-toggle="dropdown" href="#" role="button">Community <span class="caret"></span></a>
	<ul class="dropdown-menu navbar-menu" id="package-dropdown-menu-community">
	<li><a class="main-nav-link" href="../../community/index.html">Community</a></li>
	<li><a class="main-nav-link" href="../../community/contribute.html">Contribute</a></li>
	<li><a class="main-nav-link" href="../../community/powered_by.html">Powered By</a></li>
	<li><a class="main-nav-link" href="http://discuss.mxnet.io">Discuss</a></li>
	</ul>
	</span>
	<span id="dropdown-menu-position-anchor-version" style="position: relative"><a href="#" class="main-nav-link dropdown-toggle" data-toggle="dropdown" role="button" aria-haspopup="true" aria-expanded="true">Versions(1.1.0)<span class="caret"></span></a><ul id="package-dropdown-menu" class="dropdown-menu"><li><a class="main-nav-link" href=https://mxnet.incubator.apache.org/>1.1.0</a></li><li><a class="main-nav-link" href=https://mxnet.incubator.apache.org/versions/1.0.0/index.html>1.0.0</a></li><li><a class="main-nav-link" href=https://mxnet.incubator.apache.org/versions/0.12.1/index.html>0.12.1</a></li><li><a class="main-nav-link" href=https://mxnet.incubator.apache.org/versions/0.12.0/index.html>0.12.0</a></li><li><a class="main-nav-link" href=https://mxnet.incubator.apache.org/versions/0.11.0/index.html>0.11.0</a></li><li><a class="main-nav-link" href=https://mxnet.incubator.apache.org/versions/master/index.html>master</a></li></ul></span></nav>
	<script> function getRootPath(){ return "../../" } </script>
	<div class="burgerIcon dropdown">
	<a class="dropdown-toggle" data-toggle="dropdown" href="#" role="button">☰</a>
	<ul class="dropdown-menu" id="burgerMenu">
	<li><a href="../../install/index.html">Install</a></li>
	<li><a class="main-nav-link" href="../../tutorials/index.html">Tutorials</a></li>
	<li class="dropdown-submenu">
	<a href="#" tabindex="-1">Community</a>
	<ul class="dropdown-menu">
	<li><a href="../../community/index.html" tabindex="-1">Community</a></li>
	<li><a href="../../community/contribute.html" tabindex="-1">Contribute</a></li>
	<li><a href="../../community/powered_by.html" tabindex="-1">Powered By</a></li>
	</ul>
	</li>
	<li class="dropdown-submenu">
	<a href="#" tabindex="-1">API</a>
	<ul class="dropdown-menu">
	<li><a href="../../api/python/index.html" tabindex="-1">Python</a>
	</li>
	<li><a href="../../api/scala/index.html" tabindex="-1">Scala</a>
	</li>
	<li><a href="../../api/r/index.html" tabindex="-1">R</a>
	</li>
	<li><a href="../../api/julia/index.html" tabindex="-1">Julia</a>
	</li>
	<li><a href="../../api/c++/index.html" tabindex="-1">C++</a>
	</li>
	<li><a href="../../api/perl/index.html" tabindex="-1">Perl</a>
	</li>
	</ul>
	</li>
	<li class="dropdown-submenu">
	<a href="#" tabindex="-1">Docs</a>
	<ul class="dropdown-menu">
	<li><a href="../../tutorials/index.html" tabindex="-1">Tutorials</a></li>
	<li><a href="../../faq/index.html" tabindex="-1">FAQ</a></li>
	<li><a href="../../architecture/index.html" tabindex="-1">Architecture</a></li>
	<li><a href="https://github.com/apache/incubator-mxnet/tree/1.1.0/example" tabindex="-1">Examples</a></li>
	<li><a href="../../api/python/gluon/model_zoo.html" tabindex="-1">Gluon Model Zoo</a></li>
	</ul>
	</li>
	<li><a href="../../architecture/index.html">Architecture</a></li>
	<li><a class="main-nav-link" href="https://github.com/dmlc/mxnet">Github</a></li>
	<li id="dropdown-menu-position-anchor-version-mobile" class="dropdown-submenu" style="position: relative"><a href="#" tabindex="-1">Versions(1.1.0)</a><ul class="dropdown-menu"><li><a tabindex="-1" href=https://mxnet.incubator.apache.org/>1.1.0</a></li><li><a tabindex="-1" href=https://mxnet.incubator.apache.org/versions/1.0.0/index.html>1.0.0</a></li><li><a tabindex="-1" href=https://mxnet.incubator.apache.org/versions/0.12.1/index.html>0.12.1</a></li><li><a tabindex="-1" href=https://mxnet.incubator.apache.org/versions/0.12.0/index.html>0.12.0</a></li><li><a tabindex="-1" href=https://mxnet.incubator.apache.org/versions/0.11.0/index.html>0.11.0</a></li><li><a tabindex="-1" href=https://mxnet.incubator.apache.org/versions/master/index.html>master</a></li></ul></li></ul>
	</div>
	<div class="plusIcon dropdown">
	<a class="dropdown-toggle" data-toggle="dropdown" href="#" role="button"><span aria-hidden="true" class="glyphicon glyphicon-plus"></span></a>
	<ul class="dropdown-menu dropdown-menu-right" id="plusMenu"></ul>
	</div>
	<div id="search-input-wrap">
	<form action="../../search.html" autocomplete="off" class="" method="get" role="search">
	<div class="form-group inner-addon left-addon">
	<i class="glyphicon glyphicon-search"></i>
	<input class="form-control" name="q" placeholder="Search" type="text"/>
	</div>
	<input name="check_keywords" type="hidden" value="yes">
	<input name="area" type="hidden" value="default"/>
	</input></form>
	<div id="search-preview"></div>
	</div>
	<div id="searchIcon">
	<span aria-hidden="true" class="glyphicon glyphicon-search"></span>
	</div>
	<!-- <div id="lang-select-wrap"> -->
	<!-- <label id="lang-select-label"> -->
	<!-- <\!-- <i class="fa fa-globe"></i> -\-> -->
	<!-- <span></span> -->
	<!-- </label> -->
	<!-- <select id="lang-select"> -->
	<!-- <option value="en">Eng</option> -->
	<!-- <option value="zh">中文</option> -->
	<!-- </select> -->
	<!-- </div> -->
	<!-- <a id="mobile-nav-toggle">
	<span class="mobile-nav-toggle-bar"></span>
	<span class="mobile-nav-toggle-bar"></span>
	<span class="mobile-nav-toggle-bar"></span>
	</a> -->
	</div>
	</div>
	</div>
	<script type="text/javascript">
	$('body').css('background', 'white');
	</script>
	<div class="container">
	<div class="row">
	<div aria-label="main navigation" class="sphinxsidebar leftsidebar" role="navigation">
	<div class="sphinxsidebarwrapper">
	<ul>
	<li class="toctree-l1"><a class="reference internal" href="../../api/python/index.html">Python Documents</a></li>
	<li class="toctree-l1"><a class="reference internal" href="../../api/r/index.html">R Documents</a></li>
	<li class="toctree-l1"><a class="reference internal" href="../../api/julia/index.html">Julia Documents</a></li>
	<li class="toctree-l1"><a class="reference internal" href="../../api/c++/index.html">C++ Documents</a></li>
	<li class="toctree-l1"><a class="reference internal" href="../../api/scala/index.html">Scala Documents</a></li>
	<li class="toctree-l1"><a class="reference internal" href="../../api/perl/index.html">Perl Documents</a></li>
	<li class="toctree-l1"><a class="reference internal" href="../../faq/index.html">HowTo Documents</a></li>
	<li class="toctree-l1"><a class="reference internal" href="../../architecture/index.html">System Documents</a></li>
	<li class="toctree-l1"><a class="reference internal" href="../index.html">Tutorials</a></li>
	<li class="toctree-l1"><a class="reference internal" href="../../community/index.html">Community</a></li>
	</ul>
	</div>
	</div>
	<div class="content">
	<div class="page-tracker"></div>
	<div class="section" id="connectionist-temporal-classification">
	<span id="connectionist-temporal-classification"></span><h1>Connectionist Temporal Classification<a class="headerlink" href="#connectionist-temporal-classification" title="Permalink to this headline">¶</a></h1>
	<p><a class="reference external" href="https://www.cs.toronto.edu/~graves/icml_2006.pdf">Connectionist Temporal Classification</a> (CTC) is a cost function that is used to train Recurrent Neural Networks (RNNs) to label unsegmented input sequence data in supervised learning. For example, in a speech recognition application, using a typical cross-entropy loss, the input signal needs to be segmented into words or sub-words. However, using CTC-loss, it suffices to provide one label sequence for input sequence and the network learns both the alignment as well labeling. Baidu’s warp-ctc page contains a more detailed <a class="reference external" href="https://github.com/baidu-research/warp-ctc#introduction">introduction to CTC-loss</a>.</p>
	<div class="section" id="ctc-loss-in-mxnet">
	<span id="ctc-loss-in-mxnet"></span><h2>CTC-loss in MXNet<a class="headerlink" href="#ctc-loss-in-mxnet" title="Permalink to this headline">¶</a></h2>
	<p>MXNet supports two CTC-loss layers in Symbol API:</p>
	<ul class="simple">
	<li><code class="docutils literal"><span class="pre">mxnet.symbol.contrib.ctc_loss</span></code> is implemented in MXNet and included as part of the standard package.</li>
	<li><code class="docutils literal"><span class="pre">mxnet.symbol.WarpCTC</span></code> uses Baidu’s warp-ctc library and requires building warp-ctc library and mxnet library both from source.</li>
	</ul>
	</div>
	<div class="section" id="lstm-ocr-example">
	<span id="lstm-ocr-example"></span><h2>LSTM OCR Example<a class="headerlink" href="#lstm-ocr-example" title="Permalink to this headline">¶</a></h2>
	<p>MXNet’s example folder contains a <a class="reference external" href="https://github.com/apache/incubator-mxnet/tree/1.1.0/example/ctc">CTC example</a> for using CTC loss with an LSTM network to perform Optical Character Recognition (OCR) prediction on CAPTCHA images. The example demonstrates use of both CTC loss options, as well as inference after training using network symbol and parameter checkpoints.</p>
	</div>
	<div class="section" id="next-steps">
	<span id="next-steps"></span><h2>Next Steps<a class="headerlink" href="#next-steps" title="Permalink to this headline">¶</a></h2>
	<div class="toctree-wrapper compound">
	<ul>
	<li class="toctree-l1"><a class="reference external" href="https://mxnet.incubator.apache.org/tutorials/index.html">MXNet tutorials index</a></li>
	</ul>
	</div>
	</div>
	</div>
	</div>
	</div>
	<div aria-label="main navigation" class="sphinxsidebar rightsidebar" role="navigation">
	<div class="sphinxsidebarwrapper">
	<h3><a href="../../index.html">Table Of Contents</a></h3>
	<ul>
	<li><a class="reference internal" href="#">Connectionist Temporal Classification</a><ul>
	<li><a class="reference internal" href="#ctc-loss-in-mxnet">CTC-loss in MXNet</a></li>
	<li><a class="reference internal" href="#lstm-ocr-example">LSTM OCR Example</a></li>
	<li><a class="reference internal" href="#next-steps">Next Steps</a></li>
	</ul>
	</li>
	</ul>
	</div>
	</div>
	</div><div class="footer">
	<div class="section-disclaimer">
	<div class="container">
	<div>
	<img height="60" src="https://raw.githubusercontent.com/dmlc/web-data/master/mxnet/image/apache_incubator_logo.png"/>
	<p>
	Apache MXNet is an effort undergoing incubation at The Apache Software Foundation (ASF), <strong>sponsored by the <i>Apache Incubator</i></strong>. Incubation is required of all newly accepted projects until a further review indicates that the infrastructure, communications, and decision making process have stabilized in a manner consistent with other successful ASF projects. While incubation status is not necessarily a reflection of the completeness or stability of the code, it does indicate that the project has yet to be fully endorsed by the ASF.
	</p>
	<p>
	"Copyright © 2017-2018, The Apache Software Foundation
	Apache MXNet, MXNet, Apache, the Apache feather, and the Apache MXNet project logo are either registered trademarks or trademarks of the Apache Software Foundation."
	</p>
	</div>
	</div>
	</div>
	</div> <!-- pagename != index -->
	</div>
	<script crossorigin="anonymous" integrity="sha384-0mSbJDEHialfmuBBQP6A4Qrprq5OVfW37PRR3j5ELqxss1yVqOtnepnHVP9aJ7xS" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
	<script src="../../_static/js/sidebar.js" type="text/javascript"></script>
	<script src="../../_static/js/search.js" type="text/javascript"></script>
	<script src="../../_static/js/navbar.js" type="text/javascript"></script>
	<script src="../../_static/js/clipboard.min.js" type="text/javascript"></script>
	<script src="../../_static/js/copycode.js" type="text/javascript"></script>
	<script src="../../_static/js/page.js" type="text/javascript"></script>
	<script type="text/javascript">
	$('body').ready(function () {
	$('body').css('visibility', 'visible');
	});
	</script>
	</body>
	</html>