# Context

The basic TTS mechanics via OpenRouter are already implemented, but a technical issue has been discovered: when sending a single letter for voice generation, OpenRouter returns an HTTP 400 error.

This is critical for the primer, as high-quality audio generation of individual letters, sounds, and short phonetic units is required.

# Objective

Research and implement an alternative local TTS pipeline via a local server that can stably generate audio for single letters and other minimal units of the Vietnamese language without OpenRouter limitations.

## What needs to be tested

- which local TTS models support the Vietnamese language;
- whether they can correctly synthesize single letters, syllables, and very short strings;
- the quality of tones and phonetics;
- the feasibility of running the model on a local server;
- the API for calls from vietnamguru.ru;
- audio formats and generation latency;
- hardware requirements;
- licenses and usage restrictions;
- the possibility of batch generation of the voiceover dictionary;
- compatibility with the existing audio file and metadata storage system.

## Proposed Architecture

vietnamguru.ru → local TTS API → local model → audio file → existing voiceover dictionary/storage.

The local mechanism should be treated as a source audio generator; generated recordings, just like in the main TTS pipeline, should be saved and reused rather than synthesized on every playback.

## Acceptance Criteria

Find and verify a local generation method that stably accepts single letters and short phonetic elements of the Vietnamese language and produces sound of sufficient quality for further verification by a native speaker.

Bypass the OpenRouter limitation when generating audio for single letters and test a local TTS pipeline for the Vietnamese language via a dedicated server.

Research and implement local TTS voice generation via a local server

## Initial Working Result

A GraphQL resolver for the local Vietnamese TTS has been implemented. An admin page has also been created, providing an overview of letters, combinations, syllables, and their meanings/audio generation.

In other words, the basic technical framework is already functioning: local synthesis can be called via the API, and learning units can be viewed and verified within a single interface.

Refining the interface, data structure, audio quality/validation, and the learning scenario itself will still be required before reaching the end-user system, but the initial working result is already in place.

Worklog for task "Research and implement local TTS voice generation via a local server"

Initial Working Result

Task: Research and implement local TTS voice generation via a local server