retro-ru-tts 1.0.5

Retro Russian speech synthesizer (ru_tts) wrapped for Python

retro-ru-tts

Читать на русском | GitHub

Python wrapper for the ru_tts speech synthesizer — a compact, portable Russian TTS engine written in pure C.

The core is a reverse-engineered reimplementation of the SDRV resident speech driver (BelSInt lab, Institute of Technical Cybernetics, Academy of Sciences of the Byelorussian SSR, 1990). It uses formant (diphone) synthesis: no ML models, no GPU, no large dependencies — just simple, fast, deterministic speech generation.

Quick start

pip install retro-ru-tts

# Optional: ru-normalizr for advanced normalization (Python ≥ 3.10)
pip install retro-ru-tts[normalize]

import retro_ru_tts

# Synthesize and play through speakers
retro_ru_tts.synthesize("Привет, мир!")

# Get raw PCM data without playing
pcm = retro_ru_tts.synthesize("Привет", play=False)

# Save to WAV file
wav = retro_ru_tts.pcm_to_wav(pcm)
with open("output.wav", "wb") as f:
    f.write(wav)

API

synthesize(text, ...)

retro_ru_tts.synthesize(
    "Привет, мир!",

    # Voice parameters
    speech_rate=100,     # speech rate (20–500)
    voice_pitch=100,     # voice pitch (50–300)
    intonation=100,      # expressiveness (0–140)

    # Gap factors (pause duration between clauses, default 100)
    general_gap_factor=100,
    comma_gap_factor=100,
    dot_gap_factor=100,
    semicolon_gap_factor=100,
    colon_gap_factor=100,
    question_gap_factor=100,
    exclamation_gap_factor=100,
    intonational_gap_factor=100,

    # Control flags (bitmask)
    flags=3,             # default: DEC_SEP_POINT | DEC_SEP_COMMA

    # Behaviour
    wave_buffer_size=8192,  # internal buffer (256–1048576)
    play=True,              # play through speakers
    normalize=True,         # text normalization (see below)
)

Returns: bytes — raw signed 8-bit PCM audio at 10 kHz, mono.

play(text, ...)

Shortcut for synthesize(text, play=True). Same parameters (except play).

pcm_to_wav(pcm_bytes)

Wraps raw signed 8-bit PCM into a WAV container.

Returns: bytes — complete WAV file (8-bit, 10 kHz, mono).

Flags

The flags parameter is a bitmask controlling decimal separation and voice:

Flag	Value	Description
DEC_SEP_POINT	1	Treat . as decimal separator (e.g., 3.14)
DEC_SEP_COMMA	2	Treat , as decimal separator (e.g., 3,14)
USE_ALTERNATIVE_VOICE	4	Use alternative (female) voice
USE_LEGACY_RATE_ALGO	8	Use legacy linear interpolation rate algorithm instead of adaptive crossfade

Default value is 3 (DEC_SEP_POINT \| DEC_SEP_COMMA), which means both . and , are accepted as decimal separators.

To use the female voice without decimal comma: flags=5 (DEC_SEP_POINT \| USE_ALTERNATIVE_VOICE).

Text normalization

By default the input text is normalized before being fed to the synthesizer. This converts numbers to words, formats dates and times, expands abbreviations, spells out uppercase acronyms letter by letter, transliterates common English words, and cleans up punctuation.

If ru-normalizr is installed (pip install retro-ru-tts[normalize]), it is used for normalization. Otherwise, a built-in normalizer handles the most common cases:

Feature	Example	Output
Stress marks	ко́фе	кофе
Numbers	1234567	один миллион двести тридцать четыре тысячи пятьсот шестьдесят семь
Dates	15.03.2024	пятнадцатое марта две тысячи двадцать четыре года
Time	14:30	четырнадцать тридцать
Units	5 кг, 100 мл	пять килограмм, сто миллилитров
Temperature	-5 °C	минус пять градусов по Цельсию
Currency	300 руб., 50$	триста рублей, пятьдесят долларов
Symbols	100%, №5	сто процентов, номер пять
Abbreviations	т.д., т.е., напр.	так далее, то есть, например
Acronyms	TTS, РФ, USB	тэ тэ эс, эр эф, у эс бэ
Ordinals	1-й, 3-я	первый, третья
Decimals	3.14	три запятая одна четыре
Phone	[phone]	восемь четыре девять пять один два три четыре пять шесть семь
English	hello, world, ok	хэллоу, уорлд, окей
URLs/emails	http://example.com	ссылка / электронный адрес

# Skip normalization for raw PCM output
retro_ru_tts.synthesize("Версия 3.2", normalize=False)

PCM format

Property	Value
Format	Signed 8-bit PCM
Sample rate	10000 Hz
Channels	Mono (1)

Build from source

Prerequisites

• C compiler (GCC, Clang, MSVC)
• Python 3.7+ with setuptools
• Make (Linux) or build tools (Windows)

Steps

git clone https://github.com/Blue-Kod/retro-ru-tts.git
cd retro-ru-tts

# Development install (editable)
pip install -e .

# Build distribution package
pip install build
python -m build

PCM output data

The engine produces raw signed 8-bit PCM at a fixed 10 kHz sample rate, mono. This is a deliberately minimal, low-bandwidth format suitable for embedded systems, screen readers, and retro computing applications.

License

MIT. This wrapper is distributed under the same license as the original ru_tts by Igor Poretsky. See LICENSE for details.