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// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef COMPONENTS_LIVE_CAPTION_GREEDY_TEXT_STABILIZER_H_
#define COMPONENTS_LIVE_CAPTION_GREEDY_TEXT_STABILIZER_H_
#include <string>
#include <unordered_map>
#include <vector>
namespace captions {
// Predicts the stable count of streaming token sequences.
// This class has no knowledge of future partial results. It simply
// receives one partial at a time and is forced to make a prediction on
// the number of stable tokens using only the past partial results.
// Implementation based off of https://goto.google.com/w2t.
class GreedyTextStabilizer {
public:
// Initializes min_token_frequency and sets it to 0 if it is non-negative.
explicit GreedyTextStabilizer(int min_token_frequency);
~GreedyTextStabilizer();
// Updates the internal structure that determines the number of stable tokens
// and returns the stable text.
std::string UpdateText(const std::string& input_text, bool is_final = false);
// Used by unit test only.
int GetStableTokenCount() const { return stable_token_count_; }
private:
// Minimum number of times a token must appear to be counted.
const int min_token_frequency_ = 0;
// List of token counts at different locations in the sequence.
std::vector<std::unordered_map<std::string, int>> tokens_histograms_;
std::string stable_text_ = "";
int max_stable_token_count_ = 0;
int stable_token_count_ = 0;
void Reset();
// Divides a string of text into individual tokens independent of language.
std::vector<std::string> Tokenize(const std::string& input_text);
// Checks whether the input token is a mode of the token histogram.
bool IsMode(const std::string& token,
const std::unordered_map<std::string, int>& token_histogram);
};
} // namespace captions
#endif // COMPONENTS_LIVE_CAPTION_GREEDY_TEXT_STABILIZER_H_
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