haqumei 0.8.0

Haqumei is a Japanese Grapheme-to-Phoneme (G2P) library implemented in Rust.
Documentation

Table of Contents

Features

  • Word-Phoneme Mapping APIs: Provides mapping information between words ($\approx$ surface forms / dictionary entries) and phonemes, which was previously difficult to obtain directly. Enables retrieval of detailed analysis results with minimal loss of information from the input text, including unknown-word information. (See Advanced Features)
  • Prosody Information Retrieval: Provides phoneme sequences annotated with prosodic symbols, along with near-lossless mappings to the input text (g2p_prosody, g2p_mapping_prosody). (For more details, see Prosody Features.)
  • More Detailed Phoneme Labels: Through allophone resolution for moraic nasals (撥音) and geminate consonants (促音), you can choose from several options for the allophones introduced as dedicated phoneme labels. (See here for details.)
  • Performance: Enables fast processing through a native Rust implementation. (See Benchmark)
  • Accuracy: Improves accuracy by incorporating English pronunciation estimation via haqumei-kanalizer and other corrections, alongside various techniques from pyopenjtalk-plus. (See Accuracy)
  • Concurrency: Enables concurrent G2P processing across multiple threads using the *_batch methods.
  • Diverse Options: Using HaqumeiOptions, you can flexibly customize allophone phoneme label introduction, Unicode normalization, and reading behavior.

Examples can be found in haqumei/examples.

Install

Rust

During the initial build of haqumei, the dictionary is downloaded and embedded into the binary due to the file size limits on crates.io. For custom dictionaries, or for environments where network access is unavailable during the build, please refer to here.

cargo add haqumei

Python

pip install haqumei

Supported Platforms

Pre-built wheels are available for the following platforms:

OS Architecture
Linux x86_64, aarch64
macOS aarch64 (e.g., Apple Silicon M1/M2/M3)
Windows x86_64

Pre-built wheels bundle the embedded dictionary and require no network access during installation.

If a wheel is unavailable for your platform, installation falls back to building from source, which requires a Rust toolchain. In that case, the dictionary is downloaded and embedded during the build (same as the Rust crate build process).

Command-Line Tool

We also provide haqumei-cli, a command-line interface for text processing from the terminal. For detailed usage, including pipeline processing and JSON output, please see haqumei-cli/README.md

cargo install haqumei-cli

Usage

Rust

use haqumei::Haqumei;

fn main() -> Result<(), Box<dyn std::error::Error>> {
  let mut haqumei = Haqumei::new()?;

  let text = "こんにちは、世界！";

  // Convert to phoneme list
  let phonemes = haqumei.g2p(text)?;
  assert_eq!(phonemes, ["k", "o", "N", "n", "i", "ch", "i", "w", "a", "pau", "s", "e", "k", "a", "i"]);

  // Get phoneme list with prosodic symbols
  let phones = haqumei.g2p_prosody(text)?.join(" ");
  assert_eq!(phones, "^ k o [ N n i ch i w a _ s e ] k a i ! $");

  // Convert to katakana reading
  let kana = haqumei.g2k(text)?;
  assert_eq!(kana, "コンニチワ、セカイ！");

  // Enable allophone resolution
  haqumei.options.use_allophones = true;

  let text = "執筆";

  // Get Word-Phoneme mapping with prosody information
  let mapping = haqumei.g2p_mapping_prosody(text)?;
  let shippitsu = &mapping[0];
  assert_eq!(shippitsu.word, "執筆");
  assert_eq!(shippitsu.pos, "名詞");
  assert_eq!(shippitsu.accent_nucleus, 0); // Heiban (flat) type

  println!("{:?}", shippitsu.phonemes);
  // Output:
  // [Phoneme {
  //     phoneme: Sh,
  //     pitch: Some(Low)
  // },
  // Phoneme {
  //     phoneme: I,
  //     pitch: Some(Low)
  // },
  // Phoneme {
  //     phoneme: ClP, // Allophone of the geminate consonant /cl/ (Phoneme::Cl): voiceless bilabial stop
  //     pitch: Some(High)
  // },
  // Phoneme {
  //     phoneme: P,
  //     pitch: Some(High)
  // },
  // Phoneme {
  //     phoneme: UnvoicedI,
  //     pitch: Some(High)
  // }, ...]

  Ok(())
}

[!WARNING] We do not remove pitch information from devoiced vowels or from allophones introduced as dedicated phoneme labels, even in cases where no vocal-cord vibration (and thus no pitch) would be expected. As a G2P library, we believe it is better not to arbitrarily discard information, and to leave the decision of whether to drop pitch up to the user. (We shouldn't foreclose the option of keeping the pitch while converting back to a voiced vowel.)

Python

from haqumei import Haqumei

# Initialize Haqumei (the dictionary will be automatically set up)
haqumei = Haqumei()

text = "こんにちは、世界！"

# Convert to a phoneme list
phonemes = haqumei.g2p(text)
print(f"Phonemes: {phonemes}")
# -> Phonemes: ["k", "o", "N", "n", "i", "ch", "i", "w", "a", "pau", "s", "e", "k", "a", "i"]

# Get phoneme list with prosodic symbols
phones = " ".join(haqumei.g2p_prosody(text))
print(f"Prosody-annotated phonemes: {phones}")
# -> Prosody-annotated phonemes: ^ k o [ N n i ch i w a _ s e ] k a i ! $

# Convert to katakana reading
kana = haqumei.g2k(text)
print(f"Katakana reading: {kana}")
# -> Katakana reading: コンニチワ、セカイ！

Advanced Features

Word-Phoneme Mapping APIs

In Open JTalk (pyopenjtalk), unknown words are treated as pau (pauses), and Haqumei's standard g2p function follows this behavior.
However, by using G2P functions whose names contain mapping, detailed, or prosody, you can detect unknown words and spaces themselves as unk and sp respectively.

[!WARNING] Note that sp does not refer to raw space characters in the input, but rather the "記号,空白" (symbol, space) part-of-speech output by Mecab, which is normally ignored in pyopenjtalk. In particular, symbols that Mecab itself ignores (e.g., \t, \n) are not included in sp. This is why we describe the Word-Phoneme Mapping APIs as having "minimal loss relative to the input text": an exact match with the input text is not guaranteed. (Open JTalk also converts Latin characters to full-width.)

A note on the phrase "mapping words ($\approx$ surface forms / dictionary entries) to phonemes": To begin with, there is no single, universally agreed-upon definition of a "word" in Japanese. In the context of Japanese morphological analysis, a dictionary's surface form is generally treated as a "word," with grammatical function identified by analyzing the input string. During various stages of processing, Open JTalk merges NjdFeature entries carrying surface form, grammar, and accent information, and the HTS-format full-context label (which Haqumei extends) represents this abstractly as a Word. To express this, "surface form" is clearly inaccurate given the merging involved, yet we still needed a term for this split-but-processing-friendly unit, hence our deliberate use of the intentionally loose term "Word".

  • Known words: Regular phoneme sequence (punctuation marks become pau).
  • Unknown words: unk
  • Spaces, etc.: sp (Space)

Using g2p_mapping, you can obtain the phoneme-to-word mapping along with flags indicating whether a word is unknown (is_unknown) and whether it would normally be ignored in the original pipeline (is_ignored). In addition, using g2p_mapping_detailed allows you to retrieve not only the mapping but also part-of-speech information and accent details. Additionally, an API such as g2p_pairs is available for cases where unknown-word information is not needed. However, like the traditional g2p, it loses a significant amount of input information and is not particularly recommended.

To obtain words and phonemes together with prosody information, g2p_mapping_prosody is useful. See here for details. That said, keep in mind that WordPhonemeProsody, the list type returned by g2p_mapping_prosody, is essentially a superset of WordPhonemeDetail (returned by g2p_mapping_detailed), aside from Mecab's features.

In short, the amount of information provided by these APIs can be roughly ordered as: g2p_pairs < g2p_mapping < g2p_mapping_detailed < g2p_mapping_prosody

use haqumei::Haqumei;

fn main() -> Result<(), Box<dyn std::error::Error>> {
  let mut haqumei = Haqumei::new()?;

  println!("{:?}", haqumei.g2p_mapping("𰻞𰻞麺 お冷を頼んだ")?);
  // [WordPhonemeMap {
  //     word: "𰻞𰻞",
  //     phonemes: ["unk"],
  //     is_unknown: true,
  //     is_ignored: false,
  // },
  // WordPhonemeMap {
  //     word: "麺",
  //     phonemes: ["m", "e", "N"],
  //     is_unknown: false,
  //     is_ignored: false,
  // },
  // WordPhonemeMap {
  //     word: "\u{3000}",
  //     phonemes: ["sp"],
  //     is_unknown: false,
  //     is_ignored: true,
  // },
  // WordPhonemeMap {
  //     word: "お冷",
  //     phonemes: ["o", "h", "i", "y", "a"],
  //     is_unknown: false,
  //     is_ignored: false,
  // }, ... ]

  println!("{:?}", haqumei.g2p_mapping_detailed("薄明")?);
  // [WordPhonemeDetail {
  //    word: "薄明",
  //    phonemes: ["h","a","k","u","m","e","e"],
  //    features: [
  //        "薄明",
  //        "名詞",
  //        "一般",
  //        "*",
  //        "*",
  //        "*",
  //        "*",
  //        "薄明",
  //        "ハクメイ",
  //        "ハクメー",
  //        "0/4",
  //        "C2",
  //    ],
  //    pos: "名詞",
  //    pos_group1: "一般",
  //    pos_group2: "*",
  //    pos_group3: "*",
  //    ctype: "*",
  //    cform: "*",
  //    orig: "薄明",
  //    read: "ハクメイ",
  //    pron: "ハクメー",
  //    accent_nucleus: 0,
  //    mora_count: 4,
  //    chain_rule: "C2",
  //    chain_flag: -1,
  //    is_unknown: false,
  //    is_ignored: false,
  // }]

  Ok(())
}

Modifying Output with G2P Options

You can customize the behavior of Haqumei by using Haqumei::with_options. For details on the default behavior and available options, please refer to HaqumeiOptions.

In the following example, normalize_unicode (which is disabled by default) is enabled to apply Unicode NFC normalization to the input text.

use haqumei::{Haqumei, HaqumeiOptions, UnicodeNormalization};

fn main() -> Result<(), Box<dyn std::error::Error>> {
  let mut haqumei = Haqumei::with_options(HaqumeiOptions {
    normalize_unicode: UnicodeNormalization::Nfc,
    ..Default::default()
  })?;

  let text = &[
    "\u{304B}\u{3099}", // か + ゙ (が)
    "\u{306F}\u{309A}", // は + ゚ (ぱ)
    "\u{30B3}\u{3099}", // コ + ゙ (ゴ)
  ];

  println!("{:?}", haqumei.g2p_detailed_batch(text)?);
  // Output: [["g", "a"], ["p", "a"], ["g", "o"]]

  Ok(())
}

Prosody Features (g2p_prosody / g2p_mapping_prosody)

Specification of g2p_prosody_with_options

Converts the input text into a phoneme list annotated with prosodic symbols based on the ProsodyFormat setting. (The g2p_prosody method behaves identically to specifying ProsodyFormat::Default.)

The output commonly includes the following prosodic symbols:

Symbol Meaning Position
^ Beginning of utterance (BOS) Sentence-initial
$ End of utterance (EOS) Sentence-final
? End of interrogative (？) Sentence-medial
! End of exclamation (Custom extension) Sentence-medial
_ Pause / Comma (、) Sentence-medial
# Accent phrase boundary Sentence-medial
{...} Unknown word Sentence-medial

For more information on Japanese accents, please refer to the tdmelodic User Manual / Preliminary Knowledge (Japanese).

ProsodyFormat::Default

In addition to the above, the output includes the following prosodic symbols:

Symbol Meaning Position
[ Pitch rise (Phrase head) Near the beginning of a phrase
] Pitch fall (Accent nucleus) Right after the nuclear mora

The symbols [ and ] are based on the accent notation commonly used in tdmelodic and similar tools. They correspond to ^ and ! in the algorithm described by Kurihara et al. (2021) in "Prosodic Features Control by Symbols as Input of Sequence-to-Sequence Acoustic Modeling for Neural TTS".

ProsodyFormat::Prefix

Instead of using pitch rise/fall symbols ([ and ]), pitch high/low is attached as a prefix to each phoneme:

  • H_ : High pitch
  • L_ : Low pitch

The pitch is explicitly indicated for each phoneme.

Example: "青い空" -> ["^", "L_a", "H_o", "L_i", "#", "H_s", "H_o", "L_r", "L_a", "$"]

ProsodyFormat::Numeric

Pitch high/low is attached as a suffix to each phoneme as a numeric value:

  • :1 : High pitch
  • :0 : Low pitch

Example: "青い空" -> ["^", "a:0", "o:1", "i:0", "#", "s:1", "o:1", "r:0", "a:0", "$"]

Example

use haqumei::Haqumei;

fn main() -> Result<(), Box<dyn std::error::Error>> {
  let mut haqumei = Haqumei::new()?;

  let phones = haqumei.g2p_prosody("こんにちは、世界！")?;
  assert_eq!(phones.join(" "), "^ k o [ N n i ch i w a _ s e ] k a i ! $");

  let phones = haqumei.g2p_prosody("青い空、広がる。")?;
  assert_eq!(phones.join(" "), "^ a [ o ] i # s o ] r a _ h i [ r o g a r u _ $");

  Ok(())
}

Specification of g2p_mapping_prosody

On the other hand, g2p_mapping_prosody analyzes the input text and retrieves an alignment between detailed linguistic information for each morpheme (word) and phonemes with prosodic symbols.

While [Haqumei::g2p_prosody] and [Haqumei::g2p_prosody_with_options] return a flat list of strings (Vec<String>), this function returns structured data (Vec<WordPhonemeProsody>) annotated with part-of-speech, accent type, reading, and pitch information.

This is suitable for speech synthesis frontend processing when you want to maintain the correspondence between morphemes and phonemes, individually retrieve and manipulate pitch high/low ([PitchAccent]), or handle unknown words.

Information included in WordPhonemeProsody

The following information is included as data for each morpheme:

Field Description Example
word Surface form of the morpheme "空"
pos, pos_group1~3 Part-of-speech and its subdivisions "名詞", "一般"
orig, read, pron Original form, reading, pronunciation form "空", "ソラ", "ソラ"
accent_nucleus Accent nucleus position (0: Heiban type, 1~: n-th mora) 1
mora_count Number of moras 2
is_unknown Whether it was judged as an unknown word by MeCab false
is_ignored Whether no phoneme was assigned false

Prosodic Phoneme (ProsodicPhoneme)

The phonemes field contains a list of the following elements:

Variant Meaning Output symbol in g2p_prosody, etc.
Phoneme The phoneme itself and its pitch (High / Low) a, a:0, H_a, etc.
AccentPhraseBoundary Accent phrase boundary #
Pause Regular pause / comma _
Interrogative End of interrogative / Pause ?
Exclamatory End of exclamation / Pause !

Example

use haqumei::{Haqumei, PitchAccent, ProsodicPhoneme};

fn main() -> Result<(), Box<dyn std::error::Error>> {
  let mut haqumei = Haqumei::new()?;

  // Retrieve text as structured data per morpheme
  let mapping = haqumei.g2p_mapping_prosody("青い空が、好きだ！")?;

  // Morpheme information for "青い"
  let aoi = &mapping[0];
  assert_eq!(aoi.word, "青い");
  assert_eq!(aoi.pos, "形容詞");
  assert_eq!(aoi.read, "アオイ");
  assert_eq!(aoi.accent_nucleus, 2); // 中高型

  // Phoneme and pitch information for "青い" (a: Low, o: High, i: Low)
  assert!(matches!(
      aoi.phonemes[0],
      ProsodicPhoneme::Phoneme { pitch: Some(PitchAccent::Low), .. }
  ));

  let da = mapping.last().unwrap();
  assert_eq!(da.word, "！");
  assert!(da.phonemes.contains(&ProsodicPhoneme::Exclamatory));

  Ok(())
}

Accuracy

We evaluated the accuracy using the haqumei-eval crate. Below are the results:

  • Phoneme Error Rate (PER) evaluated on prj-beatrice/jsut-label, a fork of jsut-label providing annotations for the Basic5000 subset of the JSUT corpus.
  • Katakana Error Rate evaluated on ROHAN.

jsut-label

Phoneme Error Rate (S+D+I / N_expected): 1.17% (Substitute=2117, Delete=527, Insert=831, N=297843)

HaqumeiOptions:

HaqumeiOptions {
  use_unidic_yomi: true,
  normalize_iu: Some(IuPronunciation::Yuu),
  ..Default::default()
}

ROHAN

Katakana Error Rate (S+D+I / N_expected): 1.64% (Substitute=1689, Delete=493, Insert=288, N=150637)

HaqumeiOptions:

HaqumeiOptions {
  revert_long_vowels: true,
  revert_yotsugana: true,
  ..Default::default()
}

Benchmark

Here are the comparison results between pyopenjtalk (Baseline) and haqumei using approximately 318,000 characters of Japanese text.

Input data: I Am a Cat (吾輩は猫である) 318,407 chars / 8,451 lines (Average 37 chars/line) (Ruby characters have been removed)

Execution Mode Execution Time (Mean) Throughput Speedup
pyopenjtalk (Baseline) 2.358 s 135k chars/s 1.00x
haqumei (Default) 1.303 s 244k chars/s 1.81x
haqumei (g2p_batch, Default) 0.098 s 3.24M chars/s 24.04x
haqumei (Heavy) 2.101 s 151k chars/s 1.12x
haqumei (g2p_batch, Heavy) 0.268 s 1.18M chars/s 8.80x

The detailed benchmark code can be found in haqumei-bench/pyopenjtalk.

Additionally, Rust-layer benchmarks for Haqumei using Criterion.rs can be run via cargo bench in the haqumei-bench crate. The comparison benchmark with pyopenjtalk-plus is located in haqumei-bench/pyopenjtalk-plus.

Performance Notes

  • Throughput Variation by Input Structure:
    Especially in the *_batch APIs, throughput (chars/s) tends to increase as the number of characters per line grows (up to approximately 4KB), compared with pyopenjtalk. This efficiency stems from an implementation that directly extracts labels from Open JTalk's internal structures, combined with minimal FFI overhead. When processing large volumes of text, it is most efficient to pass content in substantial chunks rather than splitting it into excessively short lines.
  • Difference Between Default and Heavy:
    In the table, "Default" represents the configuration using Haqumei::new as is, while "Heavy" shows the results when predict_nani and use_unidic_yomi are enabled in HaqumeiOptions.

Building with a Custom Embedded Dictionary

By default, haqumei downloads the dictionary at build time and embeds it into the binary. This allows the crate to be published to crates.io while still producing a self-contained binary.

If you want to build with your own dictionary embedded in the binary, you can change the configuration as follows.

Change the Cargo Features

Disable the default download-dictionary feature and enable build-dictionary.

[dependencies]
haqumei = { version = "x.y.z", features = ["embed-dictionary", "build-dictionary"], default-features = false }

Prepare the Dictionary Source and Set the Environment Variable

Prepare a dictionary source directory containing .csv and .def files to be compiled at build time, then set its path to the HAQUMEI_DICT_SRC environment variable before running the build.

On Unix-like systems:

HAQUMEI_DICT_SRC="/path/to/your/dictionary" cargo build --release

On Windows (PowerShell):

& { $env:HAQUMEI_DICT_SRC="C:\path\to\your\dictionary"; cargo build --release }

Note: If the environment variable is not set, the build script falls back to dictionary, relative to the crate root.

Dictionary

Haqumei uses the dictionary included in pyopenjtalk-plus.

License

Haqumei, excluding haqumei-jlabel and haqumei-kanalizer, is distributed under the terms of the Apache License 2.0.

Licenses and Origins of Bundled Software

haqumei includes C/C++ source code and dictionary data from modified versions of Open JTalk to provide its Grapheme-to-Phoneme (G2P) functionality. The origins and licenses of this bundled code are as follows:

  • Bundled Open JTalk Source Code

    • Origin: The code contained in the vendor/open_jtalk directory is based on the tsukumijima/open_jtalk repository, which integrates improvements from various community forks (e.g., VOICEVOX project) into an enhanced version of Open JTalk.
    • License: The bundled Open JTalk source code is licensed under the Modified BSD License. This license applies only to the code located in vendor/open_jtalk, and does not apply to the rest of this project. In accordance with redistribution requirements, the full text of the Modified BSD License is included in vendor/open_jtalk/src/COPYING.

  • Bundled Dictionary Data

    • Origin: The dictionary data contained in the haqumei/dictionary directory is based on tsukumijima/pyopenjtalk-plus, a modified fork of r9y9/pyopenjtalk.
    • License: The dictionary data is covered by the license notices in haqumei/dictionary/COPYING.

  • Bundled haqumei-jlabel Source Code

    • Origin: The code contained in the haqumei-jlabel directory is based on the jpreprocess/jlabel repository.
    • License: The bundled haqumei-jlabel source code is licensed under the BSD 3-Clause License. This license applies only to the code located in haqumei-jlabel, and does not apply to the rest of this project. In accordance with redistribution requirements, the full text of the BSD 3-Clause License is included in haqumei-jlabel/LICENSE.

  • Bundled haqumei-kanalizer Crate

Acknowledgements

The fundamental design and API of haqumei are inspired by pyopenjtalk and its highly improved fork, pyopenjtalk-plus. In addition, some implementations are based on jlabel and kanalizer to improve usability and accuracy.

  • pyopenjtalk: Copyright (c) 2018 Ryuichi Yamamoto
  • pyopenjtalk-plus: Copyright (c) 2023 tsukumijima
  • jlabel: Copyright (c) 2024 JPreprocess Team
  • kanalizer: Copyright (c) 2025 VOICEVOX

We are deeply grateful to the authors and contributors of these foundational projects.