Initial commit: FunASR Speech Recognition Toolkit

Add complete FunASR codebase including models, runtime, and documentation.
2026-07-09 22:38:58 +08:00
commit 6116b1f3c6
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+// itf/transition-information.h
+
+// Copyright 2021 NVIDIA (author: Daniel Galvez)
+
+// See ../../COPYING for clarification regarding multiple authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+// THIS CODE IS PROVIDED *AS IS* BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, EITHER EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION ANY IMPLIED
+// WARRANTIES OR CONDITIONS OF TITLE, FITNESS FOR A PARTICULAR PURPOSE,
+// MERCHANTABLITY OR NON-INFRINGEMENT.
+// See the Apache 2 License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef KALDI_ITF_TRANSITION_INFORMATION_H_
+#define KALDI_ITF_TRANSITION_INFORMATION_H_
+
+#include <stdint.h>
+#include <vector>
+
+namespace kaldi {
+
+/**
+ * Class that abstracts out TransitionModel's methods originally used
+ * in the lat/ directory. By instantiating a subclass of this abstract
+ * class other than TransitionModel, you can use kaldi's lattice tools
+ * without a dependency on the hmm/ and tree/ directories. For
+ * example, you can consider creating a subclass that implements these
+ * via extracting information from Eesen's CTC T.fst object.
+ *
+ * TransitionId values must be contiguous, and starting from 1, rather
+ * than 0, since 0 corresponds to epsilon in OpenFST.
+ */
+class TransitionInformation {
+ public:
+  virtual ~TransitionInformation() {};
+  /**
+   * Returns true if trans_id1 and trans_id2 can correspond to the
+   * same phone when trans_id1 immediately precedes trans_id2 (i.e.,
+   * trans_id1 occurss at timestep t, and trans_id2 ocurs at timestep
+   * 2) (possibly with epsilons between trans_id1 and trans_id2) OR
+   * trans_id1 ocurs before trans_id2, with some number of
+   * trans_id_{k} values, all of which fulfill
+   * TransitionIdsEquivalent(trans_id1, trans_id_{k})
+   *
+   * If trans_id1 == trans_id2, it must be the case that
+   * TransitionIdsEquivalent(trans_id1, trans_id2) == true
+   */
+  virtual bool TransitionIdsEquivalent(int32_t trans_id1, int32_t trans_id2) const = 0;
+  /**
+   * Returns true if this trans_id corresponds to the start of a
+   * phone.
+   */
+  virtual bool TransitionIdIsStartOfPhone(int32_t trans_id) const = 0;
+  /**
+   * Phone is a historical term, and should be understood in a wider
+   * sense that also includes graphemes, word pieces, etc.: any
+   * minimal entity in your problem domain which is represented by a
+   * sequence of transitions with a PDF assigned to each of them by
+   * the model. In this sense, Token is a better word. Since
+   * TransitionInformation was added to subsume TransitionModel, we
+   * did not want to change the call site of every
+   * TransitionModel::TransitionIdToPhone to
+   * TransitionInformation::TransitionIdToToken.
+   */
+  virtual int32_t TransitionIdToPhone(int32_t trans_id) const = 0;
+  /**
+   * Returns true if the destination of any edge with this trans_id
+   * as its ilabel is a final state (or if a final state is
+   * epsilon-reachable from its destination state).
+   */
+  virtual bool IsFinal(int32_t trans_id) const = 0;
+  /**
+   * Returns true if *all* of the FST edge labeled by this trans_id
+   * have the same start and end states.
+   */
+  virtual bool IsSelfLoop(int32_t trans_id) const = 0;
+  int32_t TransitionIdToPdf(int32_t trans_id) const {
+    return TransitionIdToPdfArray()[trans_id];
+  }
+  /**
+   * Returns the contiguous array that backs calls to
+   * TransitionIdToPdf().
+   *
+   * Ideally, this would return a std::span, but it doesn't because
+   * kaldi doesn't support C++20 at the time this interface was
+   * written.
+   */
+  virtual const std::vector<int32_t>& TransitionIdToPdfArray() const = 0;
+  int32_t NumTransitionIds() const {
+      return TransitionIdToPdfArray().size() - 1;
+  }
+  /**
+   * Return the number of distinct outputs from
+   * TransitionIdToPdf(). Another way to look at this is as the number
+   * of outputs over which your acoustic model does a softmax.
+   */
+  virtual int32_t NumPdfs() const = 0;
+};
+
+}  // namespace kaldi
+
+#endif // KALDI_TRANSITION_INFORMATION_H_