SUSI Translator

A production-ready, real-time speech-to-text (transcription) and translation HTTP API built with Flask. It accepts streamed audio chunks, processes them asynchronously using a pluggable provider architecture (e.g., OpenAI, Deepgram, Whisper.cpp), and exposes REST endpoints and a modern web dashboard for clients to consume the resulting text.

High-Level Architecture

1. Audio Sources: Clients capture audio from a microphone, local file, live URL, stdin, or YouTube, and continuously POST base64 encoded chunks to the API.
2. REST API: A Flask application queues the incoming chunks safely.
3. Pluggable Providers: A background worker pulls chunks from the queue and routes them to configurable external or internal AI providers for transcription and optional translation.
4. Consumption: Clients or web dashboards poll the REST endpoints to receive live, sentence-reflowed text.

Features

• Provider Registry: Dynamically configure the transcription and translation AI models per-session. Support for OpenAI, Deepgram, and local Whisper models out-of-the-box.
• Secure by Default: Strict JWT-based authentication, IDOR (Insecure Direct Object Reference) prevention, and tenant isolation. No anonymous access is permitted.
• Rate Limiting: Built-in endpoints are protected against abuse via Redis-backed rate limiters in production.
• Queue Deduplication: Intelligently deduplicates overlapping audio chunks to optimize API utilization and lower provider costs.
• Modern Dashboard: A fully featured dashboard to configure providers, view active streams, and manage credentials.

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Prerequisites

• Python 3.10+
• uv for fast dependency management
• ffmpeg (must be installed on your PATH if using file, url, or youtube audio sources)

Setup

Note on Supertonic TTS: The server uses Supertonic 3 for text-to-speech audio generation. On the first run, it will automatically download ~250MB of ONNX models to ~/.cache/supertonic3. If you encounter rate limits or slow downloads, export a free Hugging Face token (HF_TOKEN) to your environment.

Use uv to automatically create a virtual environment (.venv/) and install all required dependencies:

uv sync

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Running the Server

1. Configure the Environment

Copy .env.example to .env in the flask/ directory.

2. Create the First Admin

Before you can log into the dashboard or configure providers, you must create a superuser:

uv run python flask/auth/create_superuser.py

3. Start the Flask Backend

uv run python flask/transcribe_server.py

The Web Dashboard and Swagger API documentation will now be available at http://127.0.0.1:5040.

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Environment Variables & Production Defaults

BREAKING CHANGE: All API clients (including transcription viewing and audio grabbing) now strictly require authentication.

Authentication

• JWT_SECRET_KEY (REQUIRED): Must be a strong, unpredictable string of ≥32 characters. The server will safely refuse to start without this set.

Production Readiness

For a production deployment, ensure the following are configured in your environment:

• JWT_COOKIE_SECURE=true (Requires the server to run over HTTPS)
• JWT_COOKIE_CSRF_PROTECT=true
• DATABASE_URL (Use PostgreSQL, not the default SQLite in production. e.g., postgresql://user:pass@localhost:5432/susi)
• RATELIMIT_STORAGE_URI (Use a Redis backend, e.g., redis://localhost:6379, not memory://)
• CORS_ALLOWED_ORIGINS (Pass explicit origins, e.g., https://yourdomain.com. Default is localhost only)
• FLASK_DEBUG=false (Never combine true with a non-loopback host — Werkzeug debugger is RCE)
• FLASK_HOST (Bind to 0.0.0.0 to expose externally, but default 127.0.0.1 is recommended if running behind a reverse proxy like Nginx)

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Database Migrations

This project uses Flask-Migrate and Alembic to handle database schema upgrades. To ensure your database has the latest tables (such as rooms), run the following commands from the flask/ directory:

cd flask
uv run python -m flask --app transcribe_server.py db upgrade

Existing deployments: If you have an existing susi.db that was created before migrations were added, the rooms table may be missing. Running db upgrade will add it without affecting your existing organizers or token_blocklist data.

Fresh installs: db upgrade must be run before starting the server for the first time, or the server will fail when attempting to write room records to the database.

Audio Grabber (Client-Side Ingestion)

The grabber script (flask/audio_grabber.py) captures audio from one of five sources and streams it to the transcription server.

| Source | Backend | Extra Requirements |

| --------- | ----------------------- | ------------------------------------- | | mic | PyAudio | a working input device | | file | pydub + ffmpeg | ffmpeg on PATH | | url | ffmpeg | ffmpeg on PATH | | stdin | raw PCM passthrough | none | | youtube | yt-dlp + ffmpeg | ffmpeg on PATH (yt-dlp via uv sync) |

Authentication Note: audio_grabber.py requires an authentication token to push data. Provide it via the GRABBER_AUTH_TOKEN environment variable or the --auth-token CLI flag. (You can generate a long-lived internal token or grab a session token from the dashboard).

Usage Examples

export GRABBER_AUTH_TOKEN="your_internal_or_session_token"

uv run python flask/audio_grabber.py mic
uv run python flask/audio_grabber.py file --path talk.mp3 --realtime
uv run python flask/audio_grabber.py url --url https://example.com/live.m3u8
uv run python flask/audio_grabber.py youtube --url https://www.youtube.com/live/EXAMPLE_ID
ffmpeg -i input.wav -f s16le -ac 1 -ar 16000 - | \
    uv run python flask/audio_grabber.py stdin

YouTube Authentication

YouTube increasingly returns:

ERROR: [youtube] <id>: Sign in to confirm you're not a bot.
       Use --cookies-from-browser or --cookies for the authentication.

This applies particularly for requests from data-center IPs, VPNs, or WSL. To bypass it, pass cookies from a logged-in YouTube session using one of these mutually exclusive flags:

# Option A: Read cookies directly from your local browser:
uv run python flask/audio_grabber.py youtube \
    --url https://www.youtube.com/watch?v=EXAMPLE_ID \
    --cookies-from-browser chrome

# Option B: Export cookies.txt (Netscape format) using a browser extension,
# then point --cookies at the file. This is required for WSL:
uv run python flask/audio_grabber.py youtube \
    --url https://www.youtube.com/watch?v=EXAMPLE_ID \
    --cookies /path/to/youtube-cookies.txt

Warning: Treat the cookies.txt file like a credential — it grants access to your YouTube account. Do not commit it to version control.

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Tests

A pytest suite for the Flask backend lives under flask/tests/.

uv sync --group dev      # one-time: install pytest into .venv
uv run pytest            # run the full suite
uv run pytest -v         # verbose