indic-tts-preprocess 0.1.1

Convert numbers and dates in Indic text to spoken words for TTS models

indic-tts-preprocess

A small Python library that fixes one specific but very annoying problem with open-source Indic TTS models: they cannot read numbers.

Models like ai4bharat/indic-parler-tts hallucinate badly when the input text contains raw digits. Feed them "1997 में" and you get garbled audio. Feed them "उन्नीस सौ सत्तानवे में" and it works perfectly.

This library does that conversion for you — numbers, years, dates — before the text ever reaches the tokenizer.

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Install

pip install indic-tts-preprocess

No dependencies. Pure Python. Works on Python 3.8 and above.

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Quick start

from indic_tts_preprocess import preprocess

# Hindi
preprocess("उनका जन्म 5 अगस्त 1997 को हुआ", "hi")
# -> "उनका जन्म पाँच अगस्त उन्नीस सौ सत्तानवे को हुआ"

# Marathi
preprocess("त्यांचा जन्म 15 ऑगस्ट 1947 रोजी झाला", "mr")
# -> "त्यांचा जन्म पंधरा ऑगस्ट एकोणीस शे सत्तेचाळीस रोजी झाला"

# English
preprocess("He was born on 15 August 1947", "en")
# -> "He was born on fifteen August nineteen forty seven"

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Supported languages

Code	Language
hi	Hindi
mr	Marathi
en	English

If you pass an unsupported language code, the text comes back unchanged — nothing crashes.

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What it handles

Date formats

Input	Language	Output
5 अगस्त 2004	hi	पाँच अगस्त दो हज़ार चार
05/08/2004	hi	पाँच अगस्त दो हज़ार चार
05-08-2004	hi	पाँच अगस्त दो हज़ार चार
15 August 1947	en	fifteen August nineteen forty seven
15/08/1947	en	fifteen August nineteen forty seven

Standalone numbers

Input	Language	Output
73	hi	तिहत्तर
1997	hi	उन्नीस सौ सत्तानवे
2024	en	two thousand twenty four
1905	en	nineteen oh five

Year handling (the tricky part)

Hindi and Marathi speakers say years in the 1900s differently from how you'd read them literally:

• 1997 → उन्नीस सौ सत्तानवे (not एक हज़ार नौ सौ सत्तानवे)

English speakers do the same:

• 1997 → nineteen ninety seven (not one thousand nine hundred ninety seven)
• 1905 → nineteen oh five

The library handles all of these correctly.

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API reference

preprocess(text, lang)

Parameter	Type	Description
text	str	The raw input text containing digits/dates
lang	str	Language code: "hi", "mr", or "en"

Returns str — the same text with all digits replaced by spoken words.

Raises TypeError if text is not a string.

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Contributing

Adding a new language is straightforward:

1. Create indic_tts_preprocess/languages/yourlang.py — look at hindi.py as a template
2. Add a preprocess(text) function and a num_to_words(n) function
3. Add the new language code in core.py
4. Add tests in tests/test_yourlang.py
5. Open a pull request

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License

MIT