retro-ru-tts 1.0.1

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

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 via ru-normalizr in TTS mode before being fed to the synthesizer. This converts numbers to words, formats dates, handles cases, transliterates English words, etc.

# Skip normalization for raw KOI8-R 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.