online-ctc-decoder.h
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// sherpa-onnx/csrc/online-ctc-decoder.h
//
// Copyright (c) 2023 Xiaomi Corporation
#ifndef SHERPA_ONNX_CSRC_ONLINE_CTC_DECODER_H_
#define SHERPA_ONNX_CSRC_ONLINE_CTC_DECODER_H_
#include <memory>
#include <vector>
#include "kaldi-decoder/csrc/faster-decoder.h"
#include "onnxruntime_cxx_api.h" // NOLINT
namespace sherpa_onnx {
class OnlineStream;
struct OnlineCtcDecoderResult {
/// Number of frames after subsampling we have decoded so far
int32_t frame_offset = 0;
/// The decoded token IDs
std::vector<int64_t> tokens;
/// timestamps[i] contains the output frame index where tokens[i] is decoded.
/// Note: The index is after subsampling
std::vector<int32_t> timestamps;
int32_t num_trailing_blanks = 0;
};
class OnlineCtcDecoder {
public:
virtual ~OnlineCtcDecoder() = default;
/** Run streaming CTC decoding given the output from the encoder model.
*
* @param log_probs A 3-D tensor of shape (N, T, vocab_size) containing
* lob_probs.
*
* @param results Input & Output parameters..
*/
virtual void Decode(Ort::Value log_probs,
std::vector<OnlineCtcDecoderResult> *results,
OnlineStream **ss = nullptr, int32_t n = 0) = 0;
virtual std::unique_ptr<kaldi_decoder::FasterDecoder> CreateFasterDecoder()
const {
return nullptr;
}
};
} // namespace sherpa_onnx
#endif // SHERPA_ONNX_CSRC_ONLINE_CTC_DECODER_H_