fm-rds-tx/CHANGELOG.md

Changelog

v0.5.0-pre

Full review implementation: HW-integration readiness, unity signal path, TX engine, spectral verification.

Architecture changes

• All signal sources (pilot, RDS, stereo) now output unity-normalized signals (peak ±1.0)
• Combiner gains are direct config values — no magic-number normalization (/0.1, /0.05 eliminated)
• Pre-emphasis moved from composite rate to audio input rate (correct signal path, efficient on SBC)
• RDS encoder: NextSample() zero-allocation hot path, fixed-size [104]uint8 bit buffer
• PI validation moved to config.Validate() — fail-loud, no silent 0x1234 fallback

New: TX Engine (internal/app/engine.go)

• Continuous chunk-based generation loop with configurable chunk duration
• Explicit Start()/Stop() — TX default is OFF
• Atomic underrun/overrun counters, chunk/sample stats
• Context-based cancellation with clean drain

New: Extended SoapyDriver interface

• Start(ctx), Stop(ctx), Capabilities(ctx), Stats() added to driver contract
• SimulatedDriver implements full interface with atomic runtime counters
• DeviceCaps struct for hardware capability reporting
• RuntimeStats struct for live telemetry

New: Rate adaptation

• backend.deviceSampleRateHz separates SDR device rate from internal composite rate
• Config.EffectiveDeviceRate() resolves to device rate or falls back to composite rate

New: Control plane upgrade

• POST /tx/start — explicit TX start (requires TXController)
• POST /tx/stop — explicit TX stop
• GET /runtime — live engine + driver telemetry
• TXController interface for decoupled engine control

New: Spectral verification

• Goertzel algorithm (dsp.GoertzelEnergy, dsp.BandEnergy)
• Blackbox tests verify 19 kHz pilot, 38 kHz stereo, 57 kHz RDS energy presence
• Blackbox tests verify suppression when stereo/RDS disabled

New: Operator truth tests

• rds.enabled=false → verified no 57 kHz energy
• fmModulationEnabled=false → verified Q=0
• limiterEnabled=false → verified higher peaks than with limiter
• stereoEnabled=false → verified no pilot/stereo energy

Config changes

• preEmphasisUS → preEmphasisTauUS (unambiguous: microseconds, not region)
• audio.sampleRate → audio.inputSampleRate (clear: input source rate)
• backend.deviceSampleRateHz added (0 = same as compositeRateHz)
• rds.pi validated at load time; empty/invalid = hard error
• rds.pty range-checked (0-31)

v0.4.0-pre

[previous changelog entries]