single C file (~620 LOC), no third-party deps beyond libpulse.
closes a receive loop for web/chat.html: a browser tab cannot read
another tab's PulseAudio state, so each peer runs zebrad locally
to forward decoded frames to ws://127.0.0.1:7777.
components inline:
* SHA-1 (RFC 3174) + base64 encode — for the WebSocket handshake;
verified against the canonical RFC 6455 example
(key dGhlIHNhbXBsZSBub25jZQ== → accept s3pPLMBiTxaQ9kYGzzhZRbK+xOo=)
* CRC-32 (IEEE 802.3) — verifies DATA + HELLO frame payloads
* UART symbol decoder with adaptive threshold:
running peak with 2-second half-life decay, threshold = 50% of peak,
falling-edge start detect, sample at 1.5..8.5 × sps from edge
* frame assembler: magic-sync ZB, type dispatch OFFER/READY/DATA/HELLO,
overflow + corrupt-length guards, resync on bad checksum
* embedded WebSocket server: TCP listener on 127.0.0.1:7777,
handshake responder, binary frames only (opcode 0x82), no masking
(server→client), any inbound data closes the client (browser
auto-reconnects); max 16 concurrent clients
* pulseaudio: pa_mainloop integration, record stream on @DEFAULT_MONITOR@
by default, PA_SAMPLE_FLOAT32LE mono @ 8 kHz, 10 ms fragsize, peak
energy extracted from |abs(sample)|
adaptive baud: starts at ZEBRA_BAUD_HANDSHAKE (50). On valid READY frame
locks in negotiated baud from payload. Matches the chat.html send path.
binds 127.0.0.1 only — never reachable from the LAN, even though the
chat.html page itself may be served over HTTPS from a public domain.
smoke tested: PA connect + stream ready + WS handshake (RFC example
verified) + clean shutdown. -Wall -Wextra clean.
Makefile: zebrad now part of `make all`; clean target updated.
README: new section documenting it.
