Obsidian Delta · donated to the DAX Foundation
Delta Signal
Audio signatures that hide your message in sound. Your text rides in the timing of a heartbeat, appears as writing in the spectrogram, sits under the mix as an inaudible watermark, and can arrive as an SSTV picture, a ggwave data chirp or modem tones. Every layer is tested through AAC and Opus at 128 kbps, the bitrates YouTube serves, and every layer decodes back out.
Test mode: payments run on Base Sepolia with test USDC. Live USDC payments switch on shortly.
Pricing (x402, USDC on Base)
| Call | Price | What you get |
|---|---|---|
POST /v1/render · MCP render_signature | $0.25 | A 48 kHz WAV (link kept 7 days) and a manifest of every layer |
POST /v1/decode · MCP decode_audio | $0.05 | Every hidden layer recovered from a WAV; SSTV pictures as PNG |
GET /v1/spec, GET /v1/card.png · MCP describe_engine, preview_card | Free | Options, limits, and a preview of the picture sting |
Revenue supports DAX Foundation initiatives.
MCP
{
"mcpServers": {
"delta-signal": { "url": "https://signal.daxfoundation.org/mcp" }
}
}
Paid tools follow the x402 MCP transport: an unpaid call returns the payment requirements; an x402-capable client pays and retries.
REST
curl -s https://signal.daxfoundation.org/v1/spec
# Any x402 client works; an unpaid request gets HTTP 402 with the payment requirements.
POST https://signal.daxfoundation.org/v1/render {"message":"SINCE 2017","duration":60,"stings":[{"type":"sstv","at":"start"}]}
POST https://signal.daxfoundation.org/v1/decode {"url":"https://example.com/your-file.wav","seed":"obsidian-delta"}
Layers
| Layer | How it hides | How to read it |
|---|---|---|
| Heartbeat cipher | One bit per beat in the lub-to-dub gap (200 or 270 ms), CRC-checked | decode |
| Spectral glyph | The message drawn as tones, 1.8–4.2 kHz or 15–17.6 kHz | Any spectrogram app |
| Prime count | Ticks counting 2, 3, 5, 7, 11, 13 | Your ears |
| Watermark | Keyed spread-spectrum at about −60 dBFS | decode with your seed |
| SSTV | A picture as Robot 36, Robot 72 or Martin M1 audio | Robot36 app, QSSTV, decode |
| ggwave | Data chirps, bit-compatible with ggwave | ggwave apps, decode |
| Modem | Bell 202, Bell 103 or RTTY tones, minimodem-compatible | minimodem, decode |
Made by Obsidian Delta, since 2017. Donated to the DAX Foundation.