Changelog

v0.4.0-pre

Full DSP chain implementation, pre-hardware milestone.

RDS encoder rewrite: standards-grade group framing (0A for PS, 2A for RadioText), CRC-10 per IEC 62106 with offset words, differential encoding, group scheduler with PS/RT cycling and A/B flag toggle
Stereo encoder: stateful 38 kHz DSB-SC subcarrier oscillator (phase-coherent across block boundaries), replaces fragile sample-indexed sin() in generator
Pre-emphasis filter: first-order IIR high-shelf, configurable τ (50 µs EU, 75 µs US, 0=off), with complementary de-emphasis for verification
FM modulator: composite-to-IQ via phase integration, configurable ±75 kHz deviation, unit-magnitude output guaranteed
MPX limiter: smooth attack/release peak limiter with hard-clip safety net
Linear-interpolation audio resampler (replaces nearest-neighbor)
Robust WAV loader with RIFF chunk scanning (handles LIST, INFO, bext, etc.)
New config fields: preEmphasisUS, maxDeviationHz, limiterEnabled, limiterCeiling, fmModulationEnabled
New patchable runtime fields via HTTP: preEmphasisUS, limiterEnabled, limiterCeiling
Comprehensive tests for all new DSP blocks

Config defaults: pre-emphasis 50µs, limiter on, FM modulation on, deviation ±75kHz, RDS injection 0.05
Offline generator wires full DSP chain: pre-emphasis → stereo encode → RDS → MPX combine → limiter → FM modulate
Dry-run output includes all new config fields
Status endpoint reports pre-emphasis, limiter, and FM modulation state

Initial pre-v1 milestone for the licensed short-term FM/RDS transmitter project.