tf.compat.v1.nn.ctc_beam_search_decoder

Performs beam search decoding on the logits given in input.

tf.compat.v1.nn.ctc_beam_search_decoder(
    inputs, sequence_length, beam_width=100, top_paths=1, merge_repeated=True
)
  • ctc_beam_search_decoder treats blanks as sequence termination
  • ctc_greedy_decoder treats blanks as regular elements

If merge_repeated is True, merge repeated classes in the output beams. This means that if consecutive entries in a beam are the same, only the first of these is emitted. That is, when the sequence is A B B * B * B (where '*' is the blank label), the return value is:

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

inputs 3-D float Tensor, size [max_time x batch_size x num_classes]. The logits.
sequence_length 1-D int32 vector containing sequence lengths, having size [batch_size].
beam_width An int scalar >= 0 (beam search beam width).
top_paths An int scalar >= 0, <= beam_width (controls output size).
merge_repeated Boolean. Default: True.

A tuple (decoded, log_probabilities) where
decoded A list of length top_paths, where decoded[j] is a SparseTensor containing the decoded outputs:

decoded[j].indices: Indices matrix (total_decoded_outputs[j] x 2) The rows store: [batch, time].

decoded[j].values: Values vector, size (total_decoded_outputs[j]). The vector stores the decoded classes for beam j.

decoded[j].dense_shape: Shape vector, size (2). The shape values are: [batch_size, max_decoded_length[j]].

log_probability A float matrix (batch_size x top_paths) containing sequence log-probabilities.