fm-rds-tx/internal/app/sim.go

package app

import (
    "context"
    "encoding/binary"
    "fmt"
    "path/filepath"
    "time"

    cfgpkg "github.com/jan/fm-rds-tx/internal/config"
    offpkg "github.com/jan/fm-rds-tx/internal/offline"
    "github.com/jan/fm-rds-tx/internal/output"
    "github.com/jan/fm-rds-tx/internal/platform"
)

func RunSimulatedTransmit(cfg cfgpkg.Config, outPath string, duration time.Duration) (string, error) {
    if outPath == "" {
        outPath = filepath.Join("build", "sim", "simulated-soapy.iqf32")
    }

    fileBackend, err := output.NewFileBackend(outPath, binary.LittleEndian, output.BackendInfo{
        Name:        "simulated-soapy-file",
        Description: "simulated soapy sink to file",
    })
    if err != nil {
        return "", err
    }
    defer fileBackend.Close(context.Background())

    soapyCfg := platform.SoapyConfig{
        BackendConfig: output.BackendConfig{
            SampleRateHz: float64(cfg.FM.CompositeRateHz),
            Channels:     2,
            IQLevel:      float32(cfg.FM.OutputDrive),
        },
        Driver:         "simulated",
        Device:         cfg.Backend.Device,
        CenterFreqHz:   cfg.FM.FrequencyMHz * 1_000_000,
        Simulated:      true,
        SimulationPath: outPath,
    }
    backend := platform.NewSoapyBackend(soapyCfg, platform.NewSimulatedDriver(fileBackend))
    if err := backend.Configure(context.Background(), soapyCfg.BackendConfig); err != nil {
        return "", err
    }

    gen := offpkg.NewGenerator(cfg)
    frame := gen.GenerateFrame(duration)
    if _, err := backend.Write(context.Background(), frame); err != nil {
        return "", err
    }
    if err := backend.Flush(context.Background()); err != nil {
        return "", err
    }
    return fmt.Sprintf("simulated transmit: backend=%s output=%s duration=%s input=%s", backend.Info().Name, outPath, duration, inputLabel(cfg)), nil
}

func inputLabel(cfg cfgpkg.Config) string {
    if cfg.Audio.InputPath != "" {
        return cfg.Audio.InputPath
    }
    return "tones"
}