deepspeech.h

#ifndef __DEEPSPEECH_H__
#define __DEEPSPEECH_H__

#include <cstddef>

namespace DeepSpeech
{

  class Private;

  class Model {
    private:
      Private* mPriv;

      /**
       * @brief Perform decoding of the logits, using basic CTC decoder or
       *        CTC decoder with KenLM enabled
       *
       * @param aNFrames       Number of timesteps to deal with
       * @param aLogits        Matrix of logits, of dimensions:
       *                       [timesteps][batch_size][num_classes]
       *
       * @param[out] String representing the decoded text.
       */
      char* decode(int aNFrames, float*** aLogits);

    public:
      /**
       * @brief An object providing an interface to a trained DeepSpeech model.
       *
       * @param aModelPath The path to the frozen model graph.
       * @param aNCep The number of cepstrum the model was trained with.
       * @param aNContext The context window the model was trained with.
       * @param aAlphabetConfigPath The path to the configuration file specifying
       *                            the alphabet used by the network. See alphabet.h.
       * @param aBeamWidth The beam width used by the decoder. A larger beam
       *                   width generates better results at the cost of decoding
       *                   time.
       */
      Model(const char* aModelPath, int aNCep, int aNContext,
            const char* aAlphabetConfigPath, int aBeamWidth);

      /**
       * @brief Frees associated resources and destroys model object.
       */
      ~Model();

      /**
       * @brief Enable decoding using beam scoring with a KenLM language model.
       *
       * @param aAlphabetConfigPath The path to the configuration file specifying
       *                            the alphabet used by the network. See alphabet.h.
       * @param aLMPath The path to the language model binary file.
       * @param aTriePath The path to the trie file build from the same vocabu-
       *                  lary as the language model binary.
       * @param aLMWeight The weight to give to language model results when sco-
       *                  ring.
       * @param aWordCountWeight The weight (penalty) to give to beams when in-
       *                         creasing the word count of the decoding.
       * @param aValidWordCountWeight The weight (bonus) to give to beams when
       *                              adding a new valid word to the decoding.
       */
      void enableDecoderWithLM(const char* aAlphabetConfigPath,
                               const char* aLMPath, const char* aTriePath,
                               float aLMWeight,
                               float aWordCountWeight,
                               float aValidWordCountWeight);

      /**
       * @brief Given audio, return a vector suitable for input to the
       *        DeepSpeech model.
       *
       * Extracts MFCC features from a given audio signal and adds the
       * appropriate amount of context to run inference on the DeepSpeech model.
       * This is equivalent to calling audioToInputVector() with the model's
       * cepstrum and context window.
       *
       * @param aBuffer A 16-bit, mono raw audio signal at the appropriate
       *                sample rate.
       * @param aBufferSize The sample-length of the audio signal.
       * @param aSampleRate The sample-rate of the audio signal.
       * @param[out] aMFCC An array containing features, of shape
       *                   (@p aNFrames, ncep * ncontext). The user is
       *                   responsible for freeing the array.
       * @param[out] aNFrames (optional) The number of frames in @p aMFCC.
       * @param[out] aFrameLen (optional) The length of each frame
       *                       (ncep * ncontext) in @p aMFCC.
       */
      void getInputVector(const short* aBuffer,
                          unsigned int aBufferSize,
                          int aSampleRate,
                          float** aMfcc,
                          int* aNFrames = NULL,
                          int* aFrameLen = NULL);

      /**
       * @brief Run inference on the given audio.
       *
       * Runs inference on the given input vector with the model.
       * See getInputVector().
       *
       * @param aMfcc MFCC features with the appropriate amount of context per
       *              frame.
       * @param aNFrames The number of frames in @p aMfcc.
       * @param aFrameLen (optional) The length of each frame in @p aMfcc. If
       *                  specified, this will be used to verify the array is
       *                  large enough.
       *
       * @return The resulting string after running inference. The user is
       *         responsible for freeing this string.
       */
      char* infer(float* aMfcc,
                  int aNFrames,
                  int aFrameLen = 0);

      /**
       * @brief Use the DeepSpeech model to perform Speech-To-Text.
       *
       * @param aBuffer A 16-bit, mono raw audio signal at the appropriate
       *                sample rate.
       * @param aBufferSize The number of samples in the audio signal.
       * @param aSampleRate The sample-rate of the audio signal.
       *
       * @return The STT result. The user is responsible for freeing the string.
       */
      char* stt(const short* aBuffer,
                unsigned int aBufferSize,
                int aSampleRate);
  };

}

#endif /* __DEEPSPEECH_H__ */