title: ctc loss error - sequence_length(0) <= 3
body: <p>i am facing an error similar to the one stated here <a href="https://stackoverflow.com/questions/43422949/ctc-loss-invalidargumenterror-sequence-lengthb-time">CTC Loss InvalidArgumentError: sequence_length(b) &lt;= time</a> but there seems to be no explanation of what the error actually means. Based on the reading i did, does it mean that the sequence length 
  of the example "0" in the minibatch is less than 3 ? in which case why is it an error (since as explained in the tf doc and the question above, the length of all sequences has to be lesser than time, right ?) ..could anyone kindly explain how i could debug the issue and make sense of the error? i am using an existing conv2d example and trying to merge ctc loss using some audio files i had</p>
  
  <p>the code is present here <a href="https://github.com/takingstock/ServerSide-Algos/blob/master/ctc-conv.py" rel="nofollow noreferrer">https://github.com/takingstock/ServerSide-Algos/blob/master/ctc-conv.py</a> and the problem occurs on line 213 (<em>apologies for pasting the code github url instead of the code here..i felt it might be cleaner this way</em>)</p>
  
  <p>the stack trace </p>
  
  <pre><code>Caused by op u'CTCLoss', defined at:
  File "conv_train.py", line 279, in &lt;module&gt;
  loss = tf.nn.ctc_loss(Y , logits, seq_len)
  File "/usr/local/lib/python2.7/site-packages/tensorflow/python/ops/ctc_ops.py", line 156, in ctc_loss
  ignore_longer_outputs_than_inputs=ignore_longer_outputs_than_inputs)
  File "/usr/local/lib/python2.7/site-packages/tensorflow/python/ops/gen_ctc_ops.py", line 224, in _ctc_loss
  name=name)
  File "/usr/local/lib/python2.7/site-packages/tensorflow/python/framework/op_def_library.py", line 787, in _apply_op_helper
  op_def=op_def)
  File "/usr/local/lib/python2.7/site-packages/tensorflow/python/framework/ops.py", line 3160, in create_op
  op_def=op_def)
  File "/usr/local/lib/python2.7/site-packages/tensorflow/python/framework/ops.py", line 1625, in __init__
  self._traceback = self._graph._extract_stack()  # pylint: disable=protected-access
  
  InvalidArgumentError (see above for traceback): sequence_length(0) &lt;= 3
       [[Node: CTCLoss = CTCLoss[ctc_merge_repeated=true, ignore_longer_outputs_than_inputs=false, preprocess_collapse_repeated=false, _device="/job:localhost/replica:0/task:0/device:CPU:0"](transpose, _arg_Placeholder_3_0_3, _arg_Placeholder_2_0_2, _arg_Placeholder_4_0_4)]]
  </code></pre>