CTC Loss InvalidArgumentError: sequence_length(b) <= time : <p>I am running into this error while trying to use tf.nn.ctc_loss through keras (ctc_batch_cost):</p>

<blockquote>
  <p>InvalidArgumentError (see above for traceback): sequence_length(4) &lt;= 471</p>
</blockquote>

<p>According to the documentation for tf.nn.ctc_loss, Input requirements are:</p>

<blockquote>
  <p>sequence_length(b) &lt;= time for all b</p>
  
  <p>max(labels.indices(labels.indices[:, 1] == b, 2))   &lt;=
  sequence_length(b) for all b.</p>
</blockquote>

<p>I am having a hard time understanding what this means-- what is <code>b</code> and what is <code>sequence_length(b)</code>? </p>
