# fm-rds-tx

Go-based FM stereo transmitter project with RDS.

## Status

This repository is currently at a **pre-v1, no-hardware-tested milestone**.

What works today:
- JSON configuration loading and validation
- small HTTP control/status surface
- dry-run generation for no-hardware inspection
- offline IQ/composite-style file generation
- simulated transmit path through a Soapy-oriented backend abstraction
- automated no-hardware tests and smoke checks

What does **not** work yet:
- real SDR hardware transmission
- full RDS group framing / CRC / standards-grade correctness
- real live audio ingest pipeline
- production-ready broadcast chain processing

## Project goal

Build a Go-based UKW/FM stereo transmitter with RDS that starts on Windows but is designed to stay cross-platform.

Design direction:
- Windows-first bring-up
- cross-platform architecture
- CPU-first implementation
- optional CUDA later where it actually helps
- SoapySDR-oriented backend strategy for flexibility

## Legal note

This project is intended only for lawful use within the relevant license and regulatory constraints.
RF output, deviation, filtering, spurious emissions, harmonics, and actual transmitted power must be validated on real hardware with proper measurement equipment.
Software controls are not a substitute for RF compliance work.

## Quickstart

### Print effective config

```powershell
go run ./cmd/fmrtx -print-config
```

### Dry-run (JSON summary, no hardware)

```powershell
go run ./cmd/fmrtx --dry-run --dry-output build/dryrun/frame.json
```

### Simulated transmit path (main CLI, no hardware)

```powershell
go run ./cmd/fmrtx --simulate-tx --simulate-output build/sim/simulated-soapy.iqf32 --simulate-duration 250ms
```

### Offline generator

```powershell
go run ./cmd/offline -duration 500ms -output build/offline/composite.iqf32
```

### Full local check

```powershell
powershell -ExecutionPolicy Bypass -File scripts/check.ps1
```

## Repository layout

```text
cmd/
  fmrtx/      main CLI
  offline/    offline no-hardware generator
internal/
  app/        simulated transmit path wiring
  audio/      sample/frame helpers
  config/     config schema + validation
  control/    HTTP control/status handlers
  dryrun/     JSON no-hardware summaries
  dsp/        DSP helpers
  mpx/        MPX combiner primitives
  offline/    deterministic offline composite generation
  output/     backend abstractions + file/dummy sinks
  platform/   Soapy-oriented backend abstraction
  rds/        basic RDS encoder scaffolding
  stereo/     stereo encoder primitives
examples/
  soapy_simulated/
docs/
scripts/
```

## Current release posture

Recommended current milestone tag:
- `v0.3.0-pre`

See also:
- `docs/README.md`
- `PROJECT_PLAN.md`
- `CHANGELOG.md`
- `RELEASE.md`

## Next priorities

1. real audio ingest path
2. stronger RDS implementation
3. tighter end-to-end regression coverage
4. real SoapySDR backend integration
5. first true v1.0 criteria review after those pieces exist