/TensorFlow Python



Defined in tensorflow/python/ops/ctc_ops.py.

See the guide: Neural Network > Connectionist Temporal Classification (CTC)

Performs greedy decoding on the logits given in input (best path).

Note: Regardless of the value of merge_repeated, if the maximum index of a given time and batch corresponds to the blank index (num_classes - 1), no new element is emitted.

If merge_repeated is True, merge repeated classes in output. This means that if consecutive logits' maximum indices are the same, only the first of these is emitted. The sequence A B B * B * B (where '*' is the blank label) becomes

  • A B B B if merge_repeated=True.
  • A B B B B if merge_repeated=False.


  • inputs: 3-D float Tensor sized [max_time, batch_size, num_classes]. The logits.
  • sequence_length: 1-D int32 vector containing sequence lengths, having size [batch_size].
  • merge_repeated: Boolean. Default: True.


A tuple (decoded, neg_sum_logits) where decoded: A single-element list. decoded[0] is an SparseTensor containing the decoded outputs s.t.:
decoded.indices: Indices matrix (total_decoded_outputs, 2). The rows store: [batch, time].
decoded.values: Values vector, size (total_decoded_outputs). The vector stores the decoded classes.
decoded.dense_shape: Shape vector, size (2). The shape values are: [batch_size, max_decoded_length]
neg_sum_logits: A float matrix (batch_size x 1) containing, for the sequence found, the negative of the sum of the greatest logit at each timeframe.

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Code samples licensed under the Apache 2.0 License.