Phonemis

From Text to Sound

Phonemis is a high-performance C++ library designed for Grapheme-to-Phoneme (G2P) conversion. It provides a robust pipeline for transforming raw text into phonetic transcriptions using the International Phonetic Alphabet (IPA). The library is optimized for efficiency and portability, being pure C++ with no external dependencies, which makes it easy to implement on a wide range of systems including standard and mobile applications requiring text-to-speech frontend processing.

Currently supported languages:

• 🇺🇸 English (US)
• 🇬🇧 English (British)

The Mechanics of Pronunciation

The phonemization pipeline consists of several distinct stages designed to maximize accuracy and context awareness:

1. Preprocessing: Raw input text is normalized to handle encoding issues and standard formatting.
2. Rule-based Tokenizer: The text is segmented into tokens based on linguistic rules, separating words from punctuation and handling special cases.
3. Part-of-Speech Tagging: A Hidden Markov Model (HMM) bigram tagger is employed to assign grammatical categories to words. This model is trained on the Brown Corpus to resolve homograph ambiguities based on context.
4. Viterbi Decoding: The optimal sequence of tags is determined using the Viterbi algorithm, ensuring the most probable grammatical structure is selected.
5. Lexicon-based Phonemization: Words are converted to phonemes using extensive dictionaries, with fallback mechanisms for unknown tokens.

This library is inspired by the Python package misaki.

Installation

Building with CMake

Phonemis uses CMake as its build system. To build the static library:

mkdir build
cd build
cmake ..
make

Mobile Builds

The repository includes dedicated scripts for cross-compiling the library for mobile platforms:

• Android: Use the provided Android build script to generate .a libraries for various ABIs (armeabi-v7a, arm64-v8a, x86, x86_64).
• iOS: Use the iOS build script to generate a universal static library or framework.

Sample Usage

Below is a minimalistic example demonstrating how to instantiate the pipeline and process text.

#include <phonemis/pipeline.h>
#include <phonemis/utilities/string_utils.h>
#include <iostream>

using namespace phonemis;
using namespace phonemis::utilities;

int main() {
    // Paths to required data files
    std::string tagger_path = "../data/hmm.json";
    std::string lexicon_path = "../data/dictionaries/us_merged.json";

    // Initialize pipeline for US English
    Pipeline pipeline(Lang::EN_US, tagger_path, lexicon_path);

    // Process text
    std::string text = "I love it! This is the best day of my entire life.";
    auto phonemes = pipeline.process(text);

    // Output result
    std::cout << "Text: " << text << "\n";
    std::cout << "Phonemes: " << string_utils::u32string_to_utf8(phonemes) << "\n";

    return 0;
}