aboutsummaryrefslogtreecommitdiffstats
path: root/src/DabMod.cpp
blob: 979df879fa5c313e93ff785122775dc1df1e72b6 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
/*
   Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012
   Her Majesty the Queen in Right of Canada (Communications Research
   Center Canada)

   Copyright (C) 2019
   Matthias P. Braendli, matthias.braendli@mpb.li

    http://opendigitalradio.org
 */
/*
   This file is part of ODR-DabMod.

   ODR-DabMod is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as
   published by the Free Software Foundation, either version 3 of the
   License, or (at your option) any later version.

   ODR-DabMod is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with ODR-DabMod.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifdef HAVE_CONFIG_H
#   include "config.h"
#endif

#include <memory>
#include <complex>
#include <string>
#include <iostream>
#include <iomanip>
#include <cstdlib>
#include <stdexcept>
#include <cstdio>
#include <cstring>
#include <cstddef>
#include <sys/stat.h>
#include <signal.h>

#if HAVE_NETINET_IN_H
#   include <netinet/in.h>
#endif

#include "Utils.h"
#include "Log.h"
#include "DabModulator.h"
#include "InputMemory.h"
#include "OutputFile.h"
#include "FormatConverter.h"
#include "FrameMultiplexer.h"
#include "output/SDR.h"
#include "output/UHD.h"
#include "output/Soapy.h"
#include "output/Lime.h"
#include "OutputZeroMQ.h"
#include "InputReader.h"
#include "PcDebug.h"
#include "FIRFilter.h"
#include "RemoteControl.h"
#include "ConfigParser.h"

/* UHD requires the input I and Q samples to be in the interval
 * [-1.0,1.0], otherwise they get truncated, which creates very
 * wide-spectrum spikes. Depending on the Transmission Mode, the
 * Gain Mode and the sample rate (and maybe other parameters), the
 * samples can have peaks up to about 48000. The value of 50000
 * should guarantee that with a digital gain of 1.0, UHD never clips
 * our samples.
 */
static const float normalise_factor = 50000.0f;

//Empirical normalisation factors used to normalise the samples to amplitude 1.
static const float normalise_factor_file_fix = 81000.0f;
static const float normalise_factor_file_var = 46000.0f;
static const float normalise_factor_file_max = 46000.0f;

typedef std::complex<float> complexf;

using namespace std;

volatile sig_atomic_t running = 1;

void signalHandler(int signalNb)
{
    PDEBUG("signalHandler(%i)\n", signalNb);

    running = 0;
}

struct modulator_data
{
    // For ETI
    std::shared_ptr<InputReader> inputReader;
    std::shared_ptr<EtiReader> etiReader;

    // For EDI
    std::shared_ptr<EdiInput> ediInput;

    // Common to both EDI and EDI
    uint64_t framecount = 0;
    Flowgraph *flowgraph = nullptr;
};

enum class run_modulator_state_t {
    failure,    // Corresponds to all failures
    normal_end, // Number of frames to modulate was reached
    again,      // Restart the modulator part
    reconfigure // Some sort of change of configuration we cannot handle happened
};

static run_modulator_state_t run_modulator(modulator_data& m);

static void printModSettings(const mod_settings_t& mod_settings)
{
    stringstream ss;
    // Print settings
    ss << "Input\n";
    ss << "  Type: " << mod_settings.inputTransport << "\n";
    ss << "  Source: " << mod_settings.inputName << "\n";

    ss << "Output\n";

    if (mod_settings.useFileOutput) {
        ss << "  Name: " << mod_settings.outputName << "\n";
    }
#if defined(HAVE_OUTPUT_UHD)
    else if (mod_settings.useUHDOutput) {
        ss << " UHD\n" <<
            "  Device: " << mod_settings.sdr_device_config.device << "\n" <<
            "  Subdevice: " <<
                mod_settings.sdr_device_config.subDevice << "\n" <<
            "  master_clock_rate: " <<
                mod_settings.sdr_device_config.masterClockRate << "\n" <<
            "  refclk: " <<
                mod_settings.sdr_device_config.refclk_src << "\n" <<
            "  pps source: " <<
                mod_settings.sdr_device_config.pps_src << "\n";
    }
#endif
#if defined(HAVE_SOAPYSDR)
    else if (mod_settings.useSoapyOutput) {
        ss << " SoapySDR\n"
            "  Device: " << mod_settings.sdr_device_config.device << "\n" <<
            "  master_clock_rate: " <<
                mod_settings.sdr_device_config.masterClockRate << "\n";
    }
#endif
#if defined(HAVE_LIMESDR)
    else if (mod_settings.useLimeOutput) {
        ss << " LimeSDR\n"
            "  Device: " << mod_settings.sdr_device_config.device << "\n" <<
            "  master_clock_rate: " <<
                mod_settings.sdr_device_config.masterClockRate << "\n";
    }
#endif
    else if (mod_settings.useZeroMQOutput) {
        ss << " ZeroMQ\n" <<
            "  Listening on: " << mod_settings.outputName << "\n" <<
            "  Socket type : " << mod_settings.zmqOutputSocketType << "\n";
    }

    ss << "  Sampling rate: ";
    if (mod_settings.outputRate > 1000) {
        if (mod_settings.outputRate > 1000000) {
            ss << std::fixed << std::setprecision(4) <<
                mod_settings.outputRate / 1000000.0 <<
                " MHz\n";
        }
        else {
            ss << std::fixed << std::setprecision(4) <<
                mod_settings.outputRate / 1000.0 <<
                " kHz\n";
        }
    }
    else {
        ss << std::fixed << std::setprecision(4) <<
            mod_settings.outputRate << " Hz\n";
    }
    fprintf(stderr, "%s", ss.str().c_str());
}

static shared_ptr<ModOutput> prepare_output(
        mod_settings_t& s)
{
    shared_ptr<ModOutput> output;

    if (s.useFileOutput) {
        if (s.fileOutputFormat == "complexf") {
            output = make_shared<OutputFile>(s.outputName, s.fileOutputShowMetadata);
        }
        else if (s.fileOutputFormat == "complexf_normalised") {
            if (s.gainMode == GainMode::GAIN_FIX)
                s.normalise = 1.0f / normalise_factor_file_fix;
            else if (s.gainMode == GainMode::GAIN_MAX)
                s.normalise = 1.0f / normalise_factor_file_max;
            else if (s.gainMode == GainMode::GAIN_VAR)
                s.normalise = 1.0f / normalise_factor_file_var;
            output = make_shared<OutputFile>(s.outputName, s.fileOutputShowMetadata);
        }
        else if (s.fileOutputFormat == "s16") {
            // We must normalise the samples to the interval [-32767.0; 32767.0]
            s.normalise = 32767.0f / normalise_factor;

            output = make_shared<OutputFile>(s.outputName, s.fileOutputShowMetadata);
        }
        else if (s.fileOutputFormat == "s8" or
                s.fileOutputFormat == "u8") {
            // We must normalise the samples to the interval [-127.0; 127.0]
            // The formatconverter will add 127 for u8 so that it ends up in
            // [0; 255]
            s.normalise = 127.0f / normalise_factor;

            output = make_shared<OutputFile>(s.outputName, s.fileOutputShowMetadata);
        }
        else {
            throw runtime_error("File output format " + s.fileOutputFormat +
                    " not known");
        }
    }
#if defined(HAVE_OUTPUT_UHD)
    else if (s.useUHDOutput) {
        s.normalise = 1.0f / normalise_factor;
        s.sdr_device_config.sampleRate = s.outputRate;
        auto uhddevice = make_shared<Output::UHD>(s.sdr_device_config);
        output = make_shared<Output::SDR>(s.sdr_device_config, uhddevice);
        rcs.enrol((Output::SDR*)output.get());
    }
#endif
#if defined(HAVE_SOAPYSDR)
    else if (s.useSoapyOutput) {
        /* We normalise the same way as for the UHD output */
        s.normalise = 1.0f / normalise_factor;
        s.sdr_device_config.sampleRate = s.outputRate;
        auto soapydevice = make_shared<Output::Soapy>(s.sdr_device_config);
        output = make_shared<Output::SDR>(s.sdr_device_config, soapydevice);
        rcs.enrol((Output::SDR*)output.get());
    }
#endif
#if defined(HAVE_LIMESDR)
    else if (s.useLimeOutput) {
        /* We normalise the same way as for the UHD output */
        s.normalise = 1.0f / normalise_factor;
        s.sdr_device_config.sampleRate = s.outputRate;
        auto limedevice = make_shared<Output::Lime>(s.sdr_device_config);
        output = make_shared<Output::SDR>(s.sdr_device_config, limedevice);
        rcs.enrol((Output::SDR*)output.get());
    }
#endif
#if defined(HAVE_ZEROMQ)
    else if (s.useZeroMQOutput) {
        /* We normalise the same way as for the UHD output */
        s.normalise = 1.0f / normalise_factor;
        if (s.zmqOutputSocketType == "pub") {
            output = make_shared<OutputZeroMQ>(s.outputName, ZMQ_PUB);
        }
        else if (s.zmqOutputSocketType == "rep") {
            output = make_shared<OutputZeroMQ>(s.outputName, ZMQ_REP);
        }
        else {
            std::stringstream ss;
            ss << "ZeroMQ output socket type " << s.zmqOutputSocketType << " invalid";
            throw std::invalid_argument(ss.str());
        }
    }
#endif

    return output;
}

int launch_modulator(int argc, char* argv[])
{
    int ret = 0;

    struct sigaction sa;
    memset(&sa, 0, sizeof(struct sigaction));
    sa.sa_handler = &signalHandler;

    if (sigaction(SIGINT, &sa, NULL) == -1) {
        const string errstr = strerror(errno);
        throw runtime_error("Could not set signal handler: " + errstr);
    }

    printStartupInfo();

    mod_settings_t mod_settings;
    parse_args(argc, argv, mod_settings);

    etiLog.level(info) << "Configuration parsed. Starting up version " <<
#if defined(GITVERSION)
            GITVERSION;
#else
            VERSION;
#endif

    if (not (mod_settings.useFileOutput or
             mod_settings.useUHDOutput or
             mod_settings.useZeroMQOutput or
             mod_settings.useSoapyOutput or
             mod_settings.useLimeOutput)) {
        throw std::runtime_error("Configuration error: Output not specified");
    }

    printModSettings(mod_settings);

    shared_ptr<FormatConverter> format_converter;
    if (mod_settings.useFileOutput and
            (mod_settings.fileOutputFormat == "s8" or
             mod_settings.fileOutputFormat == "u8" or
             mod_settings.fileOutputFormat == "s16")) {
        format_converter = make_shared<FormatConverter>(mod_settings.fileOutputFormat);
    }

    auto output = prepare_output(mod_settings);

    // Set thread priority to realtime
    if (int r = set_realtime_prio(1)) {
        etiLog.level(error) << "Could not set priority for modulator:" << r;
    }

    shared_ptr<InputReader> inputReader;
    shared_ptr<EdiInput> ediInput;

    if (mod_settings.inputTransport == "edi") {
        ediInput = make_shared<EdiInput>(mod_settings.tist_offset_s, mod_settings.edi_max_delay_ms);

        ediInput->ediTransport.Open(mod_settings.inputName);
        if (not ediInput->ediTransport.isEnabled()) {
            throw runtime_error("inputTransport is edi, but ediTransport is not enabled");
        }
    }
    else if (mod_settings.inputTransport == "file") {
        auto inputFileReader = make_shared<InputFileReader>();

        // Opening ETI input file
        if (inputFileReader->Open(mod_settings.inputName, mod_settings.loop) == -1) {
            throw std::runtime_error("Unable to open input");
        }

        inputReader = inputFileReader;
    }
    else if (mod_settings.inputTransport == "zeromq") {
#if !defined(HAVE_ZEROMQ)
        throw std::runtime_error("Unable to open input: "
                "ZeroMQ input transport selected, but not compiled in!");
#else
        auto inputZeroMQReader = make_shared<InputZeroMQReader>();
        inputZeroMQReader->Open(mod_settings.inputName, mod_settings.inputMaxFramesQueued);
        rcs.enrol(inputZeroMQReader.get());
        inputReader = inputZeroMQReader;
#endif
    }
    else if (mod_settings.inputTransport == "tcp") {
        auto inputTcpReader = make_shared<InputTcpReader>();
        inputTcpReader->Open(mod_settings.inputName);
        inputReader = inputTcpReader;
    }
    else {
        throw std::runtime_error("Unable to open input: "
                "invalid input transport " + mod_settings.inputTransport + " selected!");
    }

    bool run_again = true;

    while (run_again) {
        Flowgraph flowgraph(mod_settings.showProcessTime);

        modulator_data m;
        m.ediInput = ediInput;
        m.inputReader = inputReader;
        m.flowgraph = &flowgraph;

        shared_ptr<DabModulator> modulator;
        if (inputReader) {
            m.etiReader = make_shared<EtiReader>(mod_settings.tist_offset_s);
            modulator = make_shared<DabModulator>(*m.etiReader, mod_settings);
        }
        else if (ediInput) {
            modulator = make_shared<DabModulator>(ediInput->ediReader, mod_settings);
        }

        rcs.enrol(modulator.get());

        if (format_converter) {
            flowgraph.connect(modulator, format_converter);
            flowgraph.connect(format_converter, output);
        }
        else {
            flowgraph.connect(modulator, output);
        }

        if (inputReader) {
            etiLog.level(info) << inputReader->GetPrintableInfo();
        }

        run_modulator_state_t st = run_modulator(m);
        etiLog.log(trace, "DABMOD,run_modulator() = %d", st);

        switch (st) {
            case run_modulator_state_t::failure:
                etiLog.level(error) << "Modulator failure.";
                run_again = false;
                ret = 1;
                break;
            case run_modulator_state_t::again:
                etiLog.level(warn) << "Restart modulator.";
                run_again = false;
                if (auto in = dynamic_pointer_cast<InputFileReader>(inputReader)) {
                    if (in->Open(mod_settings.inputName, mod_settings.loop) == -1) {
                        etiLog.level(error) << "Unable to open input file!";
                        ret = 1;
                    }
                    else {
                        run_again = true;
                    }
                }
#if defined(HAVE_ZEROMQ)
                else if (auto in_zmq = dynamic_pointer_cast<InputZeroMQReader>(inputReader)) {
                    run_again = true;
                    // Create a new input reader
                    rcs.remove_controllable(in_zmq.get());
                    auto inputZeroMQReader = make_shared<InputZeroMQReader>();
                    inputZeroMQReader->Open(mod_settings.inputName, mod_settings.inputMaxFramesQueued);
                    rcs.enrol(inputZeroMQReader.get());
                    inputReader = inputZeroMQReader;
                }
#endif
                else if (dynamic_pointer_cast<InputTcpReader>(inputReader)) {
                    // Keep the same inputReader, as there is no input buffer overflow
                    run_again = true;
                }
                else if (ediInput) {
                    // In EDI, keep the same input
                    run_again = true;
                }
                break;
            case run_modulator_state_t::reconfigure:
                etiLog.level(warn) << "Detected change in ensemble configuration.";
                /* We can keep the input in this case */
                run_again = true;
                break;
            case run_modulator_state_t::normal_end:
            default:
                etiLog.level(info) << "modulator stopped.";
                ret = 0;
                run_again = false;
                break;
        }

        etiLog.level(info) << m.framecount << " DAB frames encoded";
        etiLog.level(info) << ((float)m.framecount * 0.024f) << " seconds encoded";
    }

    etiLog.level(info) << "Terminating";
    return ret;
}

struct zmq_input_timeout : public std::exception
{
    const char* what() const throw()
    {
        return "InputZMQ timeout";
    }
};

static run_modulator_state_t run_modulator(modulator_data& m)
{
    auto ret = run_modulator_state_t::failure;
    try {
        int last_eti_fct = -1;
        auto last_frame_received = chrono::steady_clock::now();
        Buffer data;
        if (m.inputReader) {
            data.setLength(6144);
        }

        while (running) {
            unsigned fct = 0;
            unsigned fp = 0;

            /* Load ETI data from the source */
            if (m.inputReader) {
                int framesize = m.inputReader->GetNextFrame(data.getData());

                if (framesize == 0) {
                    if (dynamic_pointer_cast<InputFileReader>(m.inputReader)) {
                        etiLog.level(info) << "End of file reached.";
                        running = 0;
                        ret = run_modulator_state_t::normal_end;
                        break;
                    }
#if defined(HAVE_ZEROMQ)
                    else if (dynamic_pointer_cast<InputZeroMQReader>(m.inputReader)) {
                        /* An empty frame marks a timeout. We ignore it, but we are
                         * now able to handle SIGINT properly.
                         *
                         * Also, we reconnect zmq every 10 seconds to avoid some
                         * issues, discussed in
                         * https://stackoverflow.com/questions/26112992/zeromq-pub-sub-on-unreliable-connection
                         *
                         * > It is possible that the PUB socket sees the error
                         * > while the SUB socket does not.
                         * >
                         * > The ZMTP RFC has a proposal for heartbeating that would
                         * > solve this problem.  The current best solution is for
                         * > PUB sockets to send heartbeats (e.g. 1 per second) when
                         * > traffic is low, and for SUB sockets to disconnect /
                         * > reconnect if they stop getting these.
                         *
                         * We don't need a heartbeat, because our application is constant frame rate,
                         * the frames themselves can act as heartbeats.
                         */

                        const auto now = chrono::steady_clock::now();
                        if (last_frame_received + chrono::seconds(10) < now) {
                            throw zmq_input_timeout();
                        }
                    }
#endif // defined(HAVE_ZEROMQ)
                    else if (dynamic_pointer_cast<InputTcpReader>(m.inputReader)) {
                        /* Same as for ZeroMQ */
                    }
                    else {
                        throw logic_error("Unhandled framesize==0!");
                    }
                    continue;
                }
                else if (framesize < 0) {
                    etiLog.level(error) << "Input read error.";
                    running = 0;
                    ret = run_modulator_state_t::normal_end;
                    break;
                }

                const int eti_bytes_read = m.etiReader->loadEtiData(data);
                if ((size_t)eti_bytes_read != data.getLength()) {
                    etiLog.level(error) << "ETI frame incompletely read";
                    throw std::runtime_error("ETI read error");
                }

                last_frame_received = chrono::steady_clock::now();

                fct = m.etiReader->getFct();
                fp = m.etiReader->getFp();
            }
            else if (m.ediInput) {
                while (running and not m.ediInput->ediReader.isFrameReady()) {
                    try {
                        bool packet_received = m.ediInput->ediTransport.rxPacket();
                        if (packet_received) {
                            last_frame_received = chrono::steady_clock::now();
                        }
                    }
                    catch (const std::runtime_error& e) {
                        etiLog.level(warn) << "EDI input: " << e.what();
                        running = 0;
                        break;
                    }

                    if (last_frame_received + chrono::seconds(10) < chrono::steady_clock::now()) {
                        etiLog.level(error) << "No EDI data received in 10 seconds.";
                        running = 0;
                        break;
                    }
                }

                if (!running) {
                    break;
                }

                fct = m.ediInput->ediReader.getFct();
                fp = m.ediInput->ediReader.getFp();
            }

            const unsigned expected_fct = (last_eti_fct + 1) % 250;
            if (last_eti_fct == -1) {
                if (fp != 0) {
                    // Do not start the flowgraph before we get to FP 0
                    // to ensure all blocks are properly aligned.
                    if (m.ediInput) {
                        m.ediInput->ediReader.clearFrame();
                    }
                    continue;
                }
                else {
                    last_eti_fct = fct;
                    m.framecount++;
                    m.flowgraph->run();
                }
            }
            else if (fct == expected_fct) {
                last_eti_fct = fct;
                m.framecount++;
                m.flowgraph->run();
            }
            else {
                etiLog.level(info) << "ETI FCT discontinuity, expected " <<
                    expected_fct << " received " << fct;
                if (m.ediInput) {
                    m.ediInput->ediReader.clearFrame();
                }
                return run_modulator_state_t::again;
            }

            if (m.ediInput) {
                m.ediInput->ediReader.clearFrame();
            }

            /* Check every once in a while if the remote control
             * is still working */
            if ((m.framecount % 250) == 0) {
                rcs.check_faults();
            }
        }
    }
    catch (const zmq_input_timeout&) {
        // The ZeroMQ input timeout
        etiLog.level(warn) << "Timeout";
        ret = run_modulator_state_t::again;
    }
    catch (const zmq_input_overflow& e) {
        // The ZeroMQ input has overflowed its buffer
        etiLog.level(warn) << e.what();
        ret = run_modulator_state_t::again;
    }
    catch (const FrameMultiplexerError& e) {
        // The FrameMultiplexer saw an error or a change in the size of a
        // subchannel. This can be due to a multiplex reconfiguration.
        etiLog.level(warn) << e.what();
        ret = run_modulator_state_t::reconfigure;
    }
    catch (const std::exception& e) {
        etiLog.level(error) << "Exception caught: " << e.what();
        ret = run_modulator_state_t::failure;
    }

    return ret;
}

int main(int argc, char* argv[])
{
    // Set timezone to UTC
    setenv("TZ", "", 1);
    tzset();

    // Version handling is done very early to ensure nothing else but the version gets printed out
    if (argc == 2 and strcmp(argv[1], "--version") == 0) {
        fprintf(stdout, "%s\n",
#if defined(GITVERSION)
                GITVERSION
#else
                PACKAGE_VERSION
#endif
               );
        return 0;
    }

    try {
        return launch_modulator(argc, argv);
    }
    catch (const std::invalid_argument& e) {
        std::string what(e.what());
        if (not what.empty()) {
            std::cerr << "Modulator error: " << what << std::endl;
        }
    }
    catch (const std::runtime_error& e) {
        std::cerr << "Modulator runtime error: " << e.what() << std::endl;
    }

    return 1;
}