git.sesse.net Git - nageru/blob - flags.cpp

   1 #include "flags.h"
   2
   3 #include <getopt.h>
   4 #include <stdio.h>
   5 #include <stdlib.h>
   6 #include <string.h>
   7
   8 #include <utility>
   9
  10 using namespace std;
  11
  12 Flags global_flags;
  13
  14 // Long options that have no corresponding short option.
  15 enum LongOption {
  16         OPTION_HELP = 1000,
  17         OPTION_MULTICHANNEL,
  18         OPTION_MIDI_MAPPING,
  19         OPTION_FAKE_CARDS_AUDIO,
  20         OPTION_HTTP_UNCOMPRESSED_VIDEO,
  21         OPTION_HTTP_X264_VIDEO,
  22         OPTION_X264_PRESET,
  23         OPTION_X264_TUNE,
  24         OPTION_X264_SPEEDCONTROL,
  25         OPTION_X264_SPEEDCONTROL_VERBOSE,
  26         OPTION_X264_BITRATE,
  27         OPTION_X264_VBV_BUFSIZE,
  28         OPTION_X264_VBV_MAX_BITRATE,
  29         OPTION_X264_PARAM,
  30         OPTION_HTTP_MUX,
  31         OPTION_HTTP_COARSE_TIMEBASE,
  32         OPTION_HTTP_AUDIO_CODEC,
  33         OPTION_HTTP_AUDIO_BITRATE,
  34         OPTION_FLAT_AUDIO,
  35         OPTION_GAIN_STAGING,
  36         OPTION_DISABLE_LOCUT,
  37         OPTION_ENABLE_LOCUT,
  38         OPTION_DISABLE_GAIN_STAGING_AUTO,
  39         OPTION_ENABLE_GAIN_STAGING_AUTO,
  40         OPTION_DISABLE_COMPRESSOR,
  41         OPTION_ENABLE_COMPRESSOR,
  42         OPTION_DISABLE_LIMITER,
  43         OPTION_ENABLE_LIMITER,
  44         OPTION_DISABLE_MAKEUP_GAIN_AUTO,
  45         OPTION_ENABLE_MAKEUP_GAIN_AUTO,
  46         OPTION_DISABLE_ALSA_OUTPUT,
  47         OPTION_NO_FLUSH_PBOS,
  48         OPTION_PRINT_VIDEO_LATENCY,
  49         OPTION_MAX_INPUT_QUEUE_FRAMES,
  50         OPTION_AUDIO_QUEUE_LENGTH_MS,
  51         OPTION_OUTPUT_YCBCR_COEFFICIENTS,
  52         OPTION_OUTPUT_BUFFER_FRAMES,
  53         OPTION_OUTPUT_SLOP_FRAMES,
  54         OPTION_TIMECODE_STREAM,
  55         OPTION_TIMECODE_STDOUT,
  56 };
  57
  58 void usage()
  59 {
  60         fprintf(stderr, "Usage: nageru [OPTION]...\n");
  61         fprintf(stderr, "\n");
  62         fprintf(stderr, "      --help                      print usage information\n");
  63         fprintf(stderr, "  -w, --width                     output width in pixels (default 1280)\n");
  64         fprintf(stderr, "  -h, --height                    output height in pixels (default 720)\n");
  65         fprintf(stderr, "  -c, --num-cards                 set number of input cards (default 2)\n");
  66         fprintf(stderr, "  -o, --output-card=CARD          also output signal to the given card (default none)\n");
  67         fprintf(stderr, "  -t, --theme=FILE                choose theme (default theme.lua)\n");
  68         fprintf(stderr, "  -I, --theme-dir=DIR             search for theme in this directory (can be given multiple times)\n");
  69         fprintf(stderr, "  -v, --va-display=SPEC           VA-API device for H.264 encoding\n");
  70         fprintf(stderr, "                                    ($DISPLAY spec or /dev/dri/render* path)\n");
  71         fprintf(stderr, "  -m, --map-signal=SIGNAL,CARD    set a default card mapping (can be given multiple times)\n");
  72         fprintf(stderr, "  -M, --input-mapping=FILE        start with the given audio input mapping (implies --multichannel)\n");
  73         fprintf(stderr, "      --multichannel              start in multichannel audio mapping mode\n");
  74         fprintf(stderr, "      --midi-mapping=FILE         start with the given MIDI controller mapping (implies --multichannel)\n");
  75         fprintf(stderr, "      --fake-cards-audio          make fake (disconnected) cards output a simple tone\n");
  76         fprintf(stderr, "      --http-uncompressed-video   send uncompressed NV12 video to HTTP clients\n");
  77         fprintf(stderr, "      --http-x264-video           send x264-compressed video to HTTP clients\n");
  78         fprintf(stderr, "      --x264-preset               x264 quality preset (default " X264_DEFAULT_PRESET ")\n");
  79         fprintf(stderr, "      --x264-tune                 x264 tuning (default " X264_DEFAULT_TUNE ", can be blank)\n");
  80         fprintf(stderr, "      --x264-speedcontrol         try to match x264 preset to available CPU speed\n");
  81         fprintf(stderr, "      --x264-speedcontrol-verbose  output speedcontrol debugging statistics\n");
  82         fprintf(stderr, "      --x264-bitrate              x264 bitrate (in kilobit/sec, default %d)\n",
  83                 DEFAULT_X264_OUTPUT_BIT_RATE);
  84         fprintf(stderr, "      --x264-vbv-bufsize          x264 VBV size (in kilobits, 0 = one-frame VBV,\n");
  85         fprintf(stderr, "                                  default: same as --x264-bitrate, that is, one-second VBV)\n");
  86         fprintf(stderr, "      --x264-vbv-max-bitrate      x264 local max bitrate (in kilobit/sec per --vbv-bufsize,\n");
  87         fprintf(stderr, "                                  0 = no limit, default: same as --x264-bitrate, i.e., CBR)\n");
  88         fprintf(stderr, "      --x264-param=NAME[,VALUE]   set any x264 parameter, for fine tuning\n");
  89         fprintf(stderr, "      --http-mux=NAME             mux to use for HTTP streams (default " DEFAULT_STREAM_MUX_NAME ")\n");
  90         fprintf(stderr, "      --http-audio-codec=NAME     audio codec to use for HTTP streams\n");
  91         fprintf(stderr, "                                  (default is to use the same as for the recording)\n");
  92         fprintf(stderr, "      --http-audio-bitrate=KBITS  audio codec bit rate to use for HTTP streams\n");
  93         fprintf(stderr, "                                  (default is %d, ignored unless --http-audio-codec is set)\n",
  94                 DEFAULT_AUDIO_OUTPUT_BIT_RATE / 1000);
  95         fprintf(stderr, "      --http-coarse-timebase      use less timebase for HTTP (recommended for muxers\n");
  96         fprintf(stderr, "                                  that handle large pts poorly, like e.g. MP4)\n");
  97         fprintf(stderr, "      --flat-audio                start with most audio processing turned off\n");
  98         fprintf(stderr, "                                    (can be overridden by e.g. --enable-limiter)\n");
  99         fprintf(stderr, "      --gain-staging=DB           set initial gain staging to the given value\n");
 100         fprintf(stderr, "                                    (--disable-gain-staging-auto)\n");
 101         fprintf(stderr, "      --disable-locut             turn off locut filter (also --enable)\n");
 102         fprintf(stderr, "      --disable-gain-staging-auto  turn off automatic gain staging (also --enable)\n");
 103         fprintf(stderr, "      --disable-compressor        turn off regular compressor (also --enable)\n");
 104         fprintf(stderr, "      --disable-limiter           turn off limiter (also --enable)\n");
 105         fprintf(stderr, "      --disable-makeup-gain-auto  turn off auto-adjustment of final makeup gain (also --enable)\n");
 106         fprintf(stderr, "      --disable-alsa-output       disable audio monitoring via ALSA\n");
 107         fprintf(stderr, "      --no-flush-pbos             do not explicitly signal texture data uploads\n");
 108         fprintf(stderr, "                                    (will give display corruption, but makes it\n");
 109         fprintf(stderr, "                                    possible to run with apitrace in real time)\n");
 110         fprintf(stderr, "      --print-video-latency       print out measurements of video latency on stdout\n");
 111         fprintf(stderr, "      --max-input-queue-frames=FRAMES  never keep more than FRAMES frames for each card\n");
 112         fprintf(stderr, "                                    (default 6, minimum 1)\n");
 113         fprintf(stderr, "      --audio-queue-length-ms=MS  length of audio resampling queue (default 100.0)\n");
 114         fprintf(stderr, "      --output-ycbcr-coefficients={rec601,rec709,auto}\n");
 115         fprintf(stderr, "                                  Y'CbCr coefficient standard of output (default auto)\n");
 116         fprintf(stderr, "                                    auto is rec709 if and only if --output-card is used\n");
 117         fprintf(stderr, "                                    and a HD resolution is set\n");
 118         fprintf(stderr, "      --output-buffer-frames=NUM  number of frames in output buffer for --output-card,\n");
 119         fprintf(stderr, "                                    can be fractional (default 6.0); note also\n");
 120         fprintf(stderr, "                                    the audio queue can't be much longer than this\n");
 121         fprintf(stderr, "      --output-slop-frames=NUM    if more less than this number of frames behind for\n");
 122         fprintf(stderr, "                                    --output-card, try to submit anyway instead of\n");
 123         fprintf(stderr, "                                    dropping the frame (default 0.5)\n");
 124         fprintf(stderr, "      --timecode-stream           show timestamp and timecode in stream\n");
 125         fprintf(stderr, "      --timecode-stdout           show timestamp and timecode on standard output\n");
 126 }
 127
 128 void parse_flags(int argc, char * const argv[])
 129 {
 130         static const option long_options[] = {
 131                 { "help", no_argument, 0, OPTION_HELP },
 132                 { "width", required_argument, 0, 'w' },
 133                 { "height", required_argument, 0, 'h' },
 134                 { "num-cards", required_argument, 0, 'c' },
 135                 { "output-card", required_argument, 0, 'o' },
 136                 { "theme", required_argument, 0, 't' },
 137                 { "theme-dir", required_argument, 0, 'I' },
 138                 { "map-signal", required_argument, 0, 'm' },
 139                 { "input-mapping", required_argument, 0, 'M' },
 140                 { "va-display", required_argument, 0, 'v' },
 141                 { "multichannel", no_argument, 0, OPTION_MULTICHANNEL },
 142                 { "midi-mapping", required_argument, 0, OPTION_MIDI_MAPPING },
 143                 { "fake-cards-audio", no_argument, 0, OPTION_FAKE_CARDS_AUDIO },
 144                 { "http-uncompressed-video", no_argument, 0, OPTION_HTTP_UNCOMPRESSED_VIDEO },
 145                 { "http-x264-video", no_argument, 0, OPTION_HTTP_X264_VIDEO },
 146                 { "x264-preset", required_argument, 0, OPTION_X264_PRESET },
 147                 { "x264-tune", required_argument, 0, OPTION_X264_TUNE },
 148                 { "x264-speedcontrol", no_argument, 0, OPTION_X264_SPEEDCONTROL },
 149                 { "x264-speedcontrol-verbose", no_argument, 0, OPTION_X264_SPEEDCONTROL_VERBOSE },
 150                 { "x264-bitrate", required_argument, 0, OPTION_X264_BITRATE },
 151                 { "x264-vbv-bufsize", required_argument, 0, OPTION_X264_VBV_BUFSIZE },
 152                 { "x264-vbv-max-bitrate", required_argument, 0, OPTION_X264_VBV_MAX_BITRATE },
 153                 { "x264-param", required_argument, 0, OPTION_X264_PARAM },
 154                 { "http-mux", required_argument, 0, OPTION_HTTP_MUX },
 155                 { "http-coarse-timebase", no_argument, 0, OPTION_HTTP_COARSE_TIMEBASE },
 156                 { "http-audio-codec", required_argument, 0, OPTION_HTTP_AUDIO_CODEC },
 157                 { "http-audio-bitrate", required_argument, 0, OPTION_HTTP_AUDIO_BITRATE },
 158                 { "flat-audio", no_argument, 0, OPTION_FLAT_AUDIO },
 159                 { "gain-staging", required_argument, 0, OPTION_GAIN_STAGING },
 160                 { "disable-locut", no_argument, 0, OPTION_DISABLE_LOCUT },
 161                 { "enable-locut", no_argument, 0, OPTION_ENABLE_LOCUT },
 162                 { "disable-gain-staging-auto", no_argument, 0, OPTION_DISABLE_GAIN_STAGING_AUTO },
 163                 { "enable-gain-staging-auto", no_argument, 0, OPTION_ENABLE_GAIN_STAGING_AUTO },
 164                 { "disable-compressor", no_argument, 0, OPTION_DISABLE_COMPRESSOR },
 165                 { "enable-compressor", no_argument, 0, OPTION_ENABLE_COMPRESSOR },
 166                 { "disable-limiter", no_argument, 0, OPTION_DISABLE_LIMITER },
 167                 { "enable-limiter", no_argument, 0, OPTION_ENABLE_LIMITER },
 168                 { "disable-makeup-gain-auto", no_argument, 0, OPTION_DISABLE_MAKEUP_GAIN_AUTO },
 169                 { "enable-makeup-gain-auto", no_argument, 0, OPTION_ENABLE_MAKEUP_GAIN_AUTO },
 170                 { "disable-alsa-output", no_argument, 0, OPTION_DISABLE_ALSA_OUTPUT },
 171                 { "no-flush-pbos", no_argument, 0, OPTION_NO_FLUSH_PBOS },
 172                 { "print-video-latency", no_argument, 0, OPTION_PRINT_VIDEO_LATENCY },
 173                 { "max-input-queue-frames", required_argument, 0, OPTION_MAX_INPUT_QUEUE_FRAMES },
 174                 { "audio-queue-length-ms", required_argument, 0, OPTION_AUDIO_QUEUE_LENGTH_MS },
 175                 { "output-ycbcr-coefficients", required_argument, 0, OPTION_OUTPUT_YCBCR_COEFFICIENTS },
 176                 { "output-buffer-frames", required_argument, 0, OPTION_OUTPUT_BUFFER_FRAMES },
 177                 { "output-slop-frames", required_argument, 0, OPTION_OUTPUT_SLOP_FRAMES },
 178                 { "timecode-stream", no_argument, 0, OPTION_TIMECODE_STREAM },
 179                 { "timecode-stdout", no_argument, 0, OPTION_TIMECODE_STDOUT },
 180                 { 0, 0, 0, 0 }
 181         };
 182         vector<string> theme_dirs;
 183         string output_ycbcr_coefficients = "auto";
 184         for ( ;; ) {
 185                 int option_index = 0;
 186                 int c = getopt_long(argc, argv, "c:t:I:v:m:M:w:h:", long_options, &option_index);
 187
 188                 if (c == -1) {
 189                         break;
 190                 }
 191                 switch (c) {
 192                 case 'w':
 193                         global_flags.width = atoi(optarg);
 194                         break;
 195                 case 'h':
 196                         global_flags.height = atoi(optarg);
 197                         break;
 198                 case 'c':
 199                         global_flags.num_cards = atoi(optarg);
 200                         break;
 201                 case 'o':
 202                         global_flags.output_card = atoi(optarg);
 203                         break;
 204                 case 't':
 205                         global_flags.theme_filename = optarg;
 206                         break;
 207                 case 'I':
 208                         theme_dirs.push_back(optarg);
 209                         break;
 210                 case 'm': {
 211                         char *ptr = strchr(optarg, ',');
 212                         if (ptr == nullptr) {
 213                                 fprintf(stderr, "ERROR: Invalid argument '%s' to --map-signal (needs a signal and a card number, separated by comma)\n", optarg);
 214                                 exit(1);
 215                         }
 216                         *ptr = '\0';
 217                         const int signal_num = atoi(optarg);
 218                         const int card_num = atoi(ptr + 1);
 219                         if (global_flags.default_stream_mapping.count(signal_num)) {
 220                                 fprintf(stderr, "ERROR: Signal %d already mapped to card %d\n",
 221                                         signal_num, global_flags.default_stream_mapping[signal_num]);
 222                                 exit(1);
 223                         }
 224                         global_flags.default_stream_mapping[signal_num] = card_num;
 225                         break;
 226                 }
 227                 case 'M':
 228                         global_flags.input_mapping_filename = optarg;
 229                         break;
 230                 case OPTION_MULTICHANNEL:
 231                         global_flags.multichannel_mapping_mode = true;
 232                         break;
 233                 case 'v':
 234                         global_flags.va_display = optarg;
 235                         break;
 236                 case OPTION_MIDI_MAPPING:
 237                         global_flags.midi_mapping_filename = optarg;
 238                         global_flags.multichannel_mapping_mode = true;
 239                         break;
 240                 case OPTION_FAKE_CARDS_AUDIO:
 241                         global_flags.fake_cards_audio = true;
 242                         break;
 243                 case OPTION_HTTP_UNCOMPRESSED_VIDEO:
 244                         global_flags.uncompressed_video_to_http = true;
 245                         break;
 246                 case OPTION_HTTP_MUX:
 247                         global_flags.stream_mux_name = optarg;
 248                         break;
 249                 case OPTION_HTTP_COARSE_TIMEBASE:
 250                         global_flags.stream_coarse_timebase = true;
 251                         break;
 252                 case OPTION_HTTP_AUDIO_CODEC:
 253                         global_flags.stream_audio_codec_name = optarg;
 254                         break;
 255                 case OPTION_HTTP_AUDIO_BITRATE:
 256                         global_flags.stream_audio_codec_bitrate = atoi(optarg) * 1000;
 257                         break;
 258                 case OPTION_HTTP_X264_VIDEO:
 259                         global_flags.x264_video_to_http = true;
 260                         break;
 261                 case OPTION_X264_PRESET:
 262                         global_flags.x264_preset = optarg;
 263                         break;
 264                 case OPTION_X264_TUNE:
 265                         global_flags.x264_tune = optarg;
 266                         break;
 267                 case OPTION_X264_SPEEDCONTROL:
 268                         global_flags.x264_speedcontrol = true;
 269                         break;
 270                 case OPTION_X264_SPEEDCONTROL_VERBOSE:
 271                         global_flags.x264_speedcontrol_verbose = true;
 272                         break;
 273                 case OPTION_X264_BITRATE:
 274                         global_flags.x264_bitrate = atoi(optarg);
 275                         break;
 276                 case OPTION_X264_VBV_BUFSIZE:
 277                         global_flags.x264_vbv_buffer_size = atoi(optarg);
 278                         break;
 279                 case OPTION_X264_VBV_MAX_BITRATE:
 280                         global_flags.x264_vbv_max_bitrate = atoi(optarg);
 281                         break;
 282                 case OPTION_X264_PARAM:
 283                         global_flags.x264_extra_param.push_back(optarg);
 284                         break;
 285                 case OPTION_FLAT_AUDIO:
 286                         // If --flat-audio is given, turn off everything that messes with the sound,
 287                         // except the final makeup gain.
 288                         global_flags.locut_enabled = false;
 289                         global_flags.gain_staging_auto = false;
 290                         global_flags.compressor_enabled = false;
 291                         global_flags.limiter_enabled = false;
 292                         break;
 293                 case OPTION_GAIN_STAGING:
 294                         global_flags.initial_gain_staging_db = atof(optarg);
 295                         global_flags.gain_staging_auto = false;
 296                         break;
 297                 case OPTION_DISABLE_LOCUT:
 298                         global_flags.locut_enabled = false;
 299                         break;
 300                 case OPTION_ENABLE_LOCUT:
 301                         global_flags.locut_enabled = true;
 302                         break;
 303                 case OPTION_DISABLE_GAIN_STAGING_AUTO:
 304                         global_flags.gain_staging_auto = false;
 305                         break;
 306                 case OPTION_ENABLE_GAIN_STAGING_AUTO:
 307                         global_flags.gain_staging_auto = true;
 308                         break;
 309                 case OPTION_DISABLE_COMPRESSOR:
 310                         global_flags.compressor_enabled = false;
 311                         break;
 312                 case OPTION_ENABLE_COMPRESSOR:
 313                         global_flags.compressor_enabled = true;
 314                         break;
 315                 case OPTION_DISABLE_LIMITER:
 316                         global_flags.limiter_enabled = false;
 317                         break;
 318                 case OPTION_ENABLE_LIMITER:
 319                         global_flags.limiter_enabled = true;
 320                         break;
 321                 case OPTION_DISABLE_MAKEUP_GAIN_AUTO:
 322                         global_flags.final_makeup_gain_auto = false;
 323                         break;
 324                 case OPTION_ENABLE_MAKEUP_GAIN_AUTO:
 325                         global_flags.final_makeup_gain_auto = true;
 326                         break;
 327                 case OPTION_DISABLE_ALSA_OUTPUT:
 328                         global_flags.enable_alsa_output = false;
 329                         break;
 330                 case OPTION_NO_FLUSH_PBOS:
 331                         global_flags.flush_pbos = false;
 332                         break;
 333                 case OPTION_PRINT_VIDEO_LATENCY:
 334                         global_flags.print_video_latency = true;
 335                         break;
 336                 case OPTION_MAX_INPUT_QUEUE_FRAMES:
 337                         global_flags.max_input_queue_frames = atoi(optarg);
 338                         break;
 339                 case OPTION_AUDIO_QUEUE_LENGTH_MS:
 340                         global_flags.audio_queue_length_ms = atof(optarg);
 341                         break;
 342                 case OPTION_OUTPUT_YCBCR_COEFFICIENTS:
 343                         output_ycbcr_coefficients = optarg;
 344                         break;
 345                 case OPTION_OUTPUT_BUFFER_FRAMES:
 346                         global_flags.output_buffer_frames = atof(optarg);
 347                         break;
 348                 case OPTION_OUTPUT_SLOP_FRAMES:
 349                         global_flags.output_slop_frames = atof(optarg);
 350                         break;
 351                 case OPTION_TIMECODE_STREAM:
 352                         global_flags.display_timecode_in_stream = true;
 353                         break;
 354                 case OPTION_TIMECODE_STDOUT:
 355                         global_flags.display_timecode_on_stdout = true;
 356                         break;
 357                 case OPTION_HELP:
 358                         usage();
 359                         exit(0);
 360                 default:
 361                         fprintf(stderr, "Unknown option '%s'\n", argv[option_index]);
 362                         fprintf(stderr, "\n");
 363                         usage();
 364                         exit(1);
 365                 }
 366         }
 367
 368         if (global_flags.uncompressed_video_to_http &&
 369             global_flags.x264_video_to_http) {
 370                 fprintf(stderr, "ERROR: --http-uncompressed-video and --http-x264-video are mutually incompatible\n");
 371                 exit(1);
 372         }
 373         if (global_flags.num_cards <= 0) {
 374                 fprintf(stderr, "ERROR: --num-cards must be at least 1\n");
 375                 exit(1);
 376         }
 377         if (global_flags.output_card < -1 ||
 378             global_flags.output_card >= global_flags.num_cards) {
 379                 fprintf(stderr, "ERROR: --output-card points to a nonexistant card\n");
 380                 exit(1);
 381         }
 382         if (global_flags.x264_speedcontrol) {
 383                 if (!global_flags.x264_preset.empty() && global_flags.x264_preset != "faster") {
 384                         fprintf(stderr, "WARNING: --x264-preset is overridden by --x264-speedcontrol (implicitly uses \"faster\" as base preset)\n");
 385                 }
 386                 global_flags.x264_preset = "faster";
 387         } else if (global_flags.x264_preset.empty()) {
 388                 global_flags.x264_preset = X264_DEFAULT_PRESET;
 389         }
 390         if (!theme_dirs.empty()) {
 391                 global_flags.theme_dirs = theme_dirs;
 392         }
 393
 394         // In reality, we could probably do with any even value (we subsample
 395         // by two in some places), but it's better to be on the safe side
 396         // wrt. video codecs and such. (I'd set 16 if I could, but 1080 isn't
 397         // divisible by 16.)
 398         if (global_flags.width <= 0 || (global_flags.width % 8) != 0 ||
 399             global_flags.height <= 0 || (global_flags.height % 8) != 0) {
 400                 fprintf(stderr, "ERROR: --width and --height must be positive integers divisible by 8\n");
 401                 exit(1);
 402         }
 403
 404         for (pair<int, int> mapping : global_flags.default_stream_mapping) {
 405                 if (mapping.second >= global_flags.num_cards) {
 406                         fprintf(stderr, "ERROR: Signal %d mapped to card %d, which doesn't exist (try adjusting --num-cards)\n",
 407                                 mapping.first, mapping.second);
 408                         exit(1);
 409                 }
 410         }
 411
 412         // Rec. 709 would be the sane thing to do, but it seems many players
 413         // just default to BT.601 coefficients no matter what. We _do_ set
 414         // the right flags, so that a player that works properly doesn't have
 415         // to guess, but it's frequently ignored. See discussions
 416         // in e.g. https://trac.ffmpeg.org/ticket/4978; the situation with
 417         // browsers is complicated and depends on things like hardware acceleration
 418         // (https://bugs.chromium.org/p/chromium/issues/detail?id=333619 for
 419         // extensive discussion). VLC generally fixed this as part of 3.0.0
 420         // (see e.g. https://github.com/videolan/vlc/commit/bc71288b2e38c07d6921472824b92eef1aa85f7e
 421         // and https://github.com/videolan/vlc/commit/c3fc2683a9cde1d42674ebf9935dced05733a215),
 422         // but earlier versions were pretty random.
 423         //
 424         // On the other hand, HDMI/SDI output typically requires Rec. 709 for
 425         // HD resolutions (with no way of signaling anything else), which is
 426         // a conflicting demand. In this case, we typically let the HDMI/SDI
 427         // output win, but the user can override this.
 428         if (output_ycbcr_coefficients == "auto") {
 429                 if (global_flags.output_card >= 0 && global_flags.width >= 1280) {
 430                         global_flags.ycbcr_rec709_coefficients = true;
 431                 } else {
 432                         global_flags.ycbcr_rec709_coefficients = false;
 433                 }
 434         } else if (output_ycbcr_coefficients == "rec709") {
 435                 global_flags.ycbcr_rec709_coefficients = true;
 436         } else if (output_ycbcr_coefficients == "rec601") {
 437                 global_flags.ycbcr_rec709_coefficients = false;
 438         } else {
 439                 fprintf(stderr, "ERROR: --output-ycbcr-coefficients must be “rec601”, “rec709” or “auto”\n");
 440                 exit(1);
 441         }
 442
 443         if (global_flags.output_buffer_frames < 0.0f) {
 444                 // Actually, even zero probably won't make sense; there is some internal
 445                 // delay to the card.
 446                 fprintf(stderr, "ERROR: --output-buffer-frames can't be negative.\n");
 447                 exit(1);
 448         }
 449         if (global_flags.output_slop_frames < 0.0f) {
 450                 fprintf(stderr, "ERROR: --output-slop-frames can't be negative.\n");
 451                 exit(1);
 452         }
 453         if (global_flags.max_input_queue_frames < 1) {
 454                 fprintf(stderr, "ERROR: --max-input-queue-frames must be at least 1.\n");
 455                 exit(1);
 456         }
 457         if (global_flags.max_input_queue_frames > 10) {
 458                 fprintf(stderr, "WARNING: --max-input-queue-frames has little effect over 10.\n");
 459         }
 460 }