Sonobraille synthesizer for NVDA

This add-on gives NVDA the voice of the Sonobraille, the MS-DOS Braille notetaker built by AYZ Ingeniería for ONCE-CIDAT in Spain in the early 2000s. The synthesizer is TTSE2SO.EXE — AUDIOLOGIC's "The Text Speaker" — and until now it had never run anywhere but on the device itself.

How it works

The engine cannot simply be loaded and called. It is encrypted on disk, it verifies itself (changing one byte of the file makes it derail), and it refuses to install unless it finds AMD Élan SC4xx hardware. So the add-on ships something else: a snapshot of a Sonobraille on which the engine is already resident and already past those checks, taken from the device's own software running under QEMU. NVDA maps that snapshot flat under the Unicorn CPU emulator and re-enters it at the engine's own entry point — INT 65h — once per utterance.

There is no DOS, no emulator process and no disk image. Synthesis runs on a worker thread at roughly twelve times real time, and each block of audio is handed to NVDA as the engine produces it, so speech starts long before a long utterance has finished rendering.

Settings

Rate, pitch, volume and inflection all work and appear on NVDA's usual 0–100 sliders. Two things are worth knowing:

• Pitch has only seven distinct steps in the engine, so neighbouring slider positions sound the same. That is the synthesizer, not the add-on.
• The rate range is generous — about 115 to 437 words per minute — so the top of the slider is genuinely fast.

The voice is Spanish

The snapshot carries the device's Spanish voice, which is what a Sonobraille shipped with. NVDA is told the voice's language is es, so automatic language switching will treat it accordingly.

Why there is no English voice

The Sonobraille does have one, and it is a different synthesizer entirely: First Byte's Text-to-Speech Engine 4.1, reached through AUDIOLOGIC's TTS20_EN shim. It installs under emulation and is reachable through the same interface as the Spanish voice — but its driver takes a job, sets an internal busy flag, and never clears it, after which it is silent for good. That happens with the device's own software driving it, not just here, so it is a bug to be found rather than a limitation of this add-on. Until then only Spanish is offered.

Provenance

TTSE2SO.EXE and the data it reads are ONCE-CIDAT / AYZ Ingeniería software. They are included here because this add-on was built for the owner of the device they came from. Nothing here is a redistribution licence.