libavformat/tee.c

   1 /*
   2  * Tee pseudo-muxer
   3  * Copyright (c) 2012 Nicolas George
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public License
   9  * as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public License
  18  * along with FFmpeg; if not, write to the Free Software * Foundation, Inc.,
  19  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22
  23 #include "libavutil/avutil.h"
  24 #include "libavutil/avstring.h"
  25 #include "libavutil/mem.h"
  26 #include "libavutil/opt.h"
  27 #include "libavcodec/bsf.h"
  28 #include "internal.h"
  29 #include "avformat.h"
  30 #include "mux.h"
  31 #include "tee_common.h"
  32
  33 typedef enum {
  34     ON_SLAVE_FAILURE_ABORT  = 1,
  35     ON_SLAVE_FAILURE_IGNORE = 2
  36 } SlaveFailurePolicy;
  37
  38 #define DEFAULT_SLAVE_FAILURE_POLICY ON_SLAVE_FAILURE_ABORT
  39
  40 typedef struct {
  41     AVFormatContext *avf;
  42     AVBSFContext **bsfs; ///< bitstream filters per stream
  43
  44     SlaveFailurePolicy on_fail;
  45     int use_fifo;
  46     AVDictionary *fifo_options;
  47
  48     /** map from input to output streams indexes,
  49      * disabled output streams are set to -1 */
  50     int *stream_map;
  51     int header_written;
  52 } TeeSlave;
  53
  54 typedef struct TeeContext {
  55     const AVClass *class;
  56     unsigned nb_slaves;
  57     unsigned nb_alive;
  58     TeeSlave *slaves;
  59     int use_fifo;
  60     AVDictionary *fifo_options;
  61 } TeeContext;
  62
  63 static const char *const slave_delim     = "|";
  64 static const char *const slave_bsfs_spec_sep = "/";
  65 static const char *const slave_select_sep = ",";
  66
  67 #define OFFSET(x) offsetof(TeeContext, x)
  68 static const AVOption options[] = {
  69         {"use_fifo", "Use fifo pseudo-muxer to separate actual muxers from encoder",
  70          OFFSET(use_fifo), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, AV_OPT_FLAG_ENCODING_PARAM},
  71         {"fifo_options", "fifo pseudo-muxer options", OFFSET(fifo_options),
  72          AV_OPT_TYPE_DICT, {.str = NULL}, 0, 0, AV_OPT_FLAG_ENCODING_PARAM},
  73         {NULL}
  74 };
  75
  76 static const AVClass tee_muxer_class = {
  77     .class_name = "Tee muxer",
  78     .item_name  = av_default_item_name,
  79     .option = options,
  80     .version    = LIBAVUTIL_VERSION_INT,
  81 };
  82
  83 static inline int parse_slave_failure_policy_option(const char *opt, TeeSlave *tee_slave)
  84 {
  85     if (!opt) {
  86         tee_slave->on_fail = DEFAULT_SLAVE_FAILURE_POLICY;
  87         return 0;
  88     } else if (!av_strcasecmp("abort", opt)) {
  89         tee_slave->on_fail = ON_SLAVE_FAILURE_ABORT;
  90         return 0;
  91     } else if (!av_strcasecmp("ignore", opt)) {
  92         tee_slave->on_fail = ON_SLAVE_FAILURE_IGNORE;
  93         return 0;
  94     }
  95     /* Set failure behaviour to abort, so invalid option error will not be ignored */
  96     tee_slave->on_fail = ON_SLAVE_FAILURE_ABORT;
  97     return AVERROR(EINVAL);
  98 }
  99
 100 static int parse_slave_fifo_policy(const char *use_fifo, TeeSlave *tee_slave)
 101 {
 102     /*TODO - change this to use proper function for parsing boolean
 103      *       options when there is one */
 104     if (av_match_name(use_fifo, "true,y,yes,enable,enabled,on,1")) {
 105         tee_slave->use_fifo = 1;
 106     } else if (av_match_name(use_fifo, "false,n,no,disable,disabled,off,0")) {
 107         tee_slave->use_fifo = 0;
 108     } else {
 109         return AVERROR(EINVAL);
 110     }
 111     return 0;
 112 }
 113
 114 static int parse_slave_fifo_options(const char *fifo_options, TeeSlave *tee_slave)
 115 {
 116     return av_dict_parse_string(&tee_slave->fifo_options, fifo_options, "=", ":", 0);
 117 }
 118
 119 static int close_slave(TeeSlave *tee_slave)
 120 {
 121     AVFormatContext *avf;
 122     int ret = 0;
 123
 124     av_dict_free(&tee_slave->fifo_options);
 125     avf = tee_slave->avf;
 126     if (!avf)
 127         return 0;
 128
 129     if (tee_slave->header_written)
 130         ret = av_write_trailer(avf);
 131
 132     if (tee_slave->bsfs) {
 133         for (unsigned i = 0; i < avf->nb_streams; ++i)
 134             av_bsf_free(&tee_slave->bsfs[i]);
 135     }
 136     av_freep(&tee_slave->stream_map);
 137     av_freep(&tee_slave->bsfs);
 138
 139     ff_format_io_close(avf, &avf->pb);
 140     avformat_free_context(avf);
 141     tee_slave->avf = NULL;
 142     return ret;
 143 }
 144
 145 static void close_slaves(AVFormatContext *avf)
 146 {
 147     TeeContext *tee = avf->priv_data;
 148
 149     for (unsigned i = 0; i < tee->nb_slaves; i++) {
 150         close_slave(&tee->slaves[i]);
 151     }
 152     av_freep(&tee->slaves);
 153 }
 154
 155 static int open_slave(AVFormatContext *avf, char *slave, TeeSlave *tee_slave)
 156 {
 157     int ret;
 158     AVDictionary *options = NULL, *bsf_options = NULL;
 159     const AVDictionaryEntry *entry;
 160     char *filename;
 161     char *format = NULL, *select = NULL;
 162     AVFormatContext *avf2 = NULL;
 163     int stream_count;
 164     int fullret;
 165     char *subselect = NULL, *next_subselect = NULL, *first_subselect = NULL, *tmp_select = NULL;
 166
 167     if ((ret = ff_tee_parse_slave_options(avf, slave, &options, &filename)) < 0)
 168         return ret;
 169
 170     tee_slave->on_fail = DEFAULT_SLAVE_FAILURE_POLICY;
 171
 172 #define CONSUME_OPTION(option, field, action) do {                      \
 173         AVDictionaryEntry *en = av_dict_get(options, option, NULL, 0);  \
 174         if (en) {                                                       \
 175             field = en->value;                                          \
 176             { action }                                                  \
 177             av_dict_set(&options, option, NULL, 0);                     \
 178         }                                                               \
 179     } while (0)
 180 #define STEAL_OPTION(option, field)                                     \
 181     CONSUME_OPTION(option, field,                                       \
 182                    en->value = NULL; /* prevent it from being freed */)
 183 #define PROCESS_OPTION(option, function, on_error) do {                 \
 184         const char *value;                                              \
 185         CONSUME_OPTION(option, value, if ((ret = function) < 0)         \
 186                                           { { on_error } goto end; });  \
 187     } while (0)
 188
 189     STEAL_OPTION("f", format);
 190     STEAL_OPTION("select", select);
 191     PROCESS_OPTION("onfail",
 192                    parse_slave_failure_policy_option(value, tee_slave),
 193                    av_log(avf, AV_LOG_ERROR, "Invalid onfail option value, "
 194                           "valid options are 'abort' and 'ignore'\n"););
 195     PROCESS_OPTION("use_fifo",
 196                    parse_slave_fifo_policy(value, tee_slave),
 197                    av_log(avf, AV_LOG_ERROR, "Error parsing fifo options: %s\n",
 198                           av_err2str(ret)););
 199     PROCESS_OPTION("fifo_options",
 200                    parse_slave_fifo_options(value, tee_slave), ;);
 201     entry = NULL;
 202     while ((entry = av_dict_get(options, "bsfs", NULL, AV_DICT_IGNORE_SUFFIX))) {
 203         /* trim out strlen("bsfs") characters from key */
 204         av_dict_set(&bsf_options, entry->key + 4, entry->value, 0);
 205         av_dict_set(&options, entry->key, NULL, 0);
 206     }
 207
 208     if (tee_slave->use_fifo) {
 209
 210         if (options) {
 211             char *format_options_str = NULL;
 212             ret = av_dict_get_string(options, &format_options_str, '=', ':');
 213             if (ret < 0)
 214                 goto end;
 215
 216             ret = av_dict_set(&tee_slave->fifo_options, "format_opts", format_options_str,
 217                               AV_DICT_DONT_STRDUP_VAL);
 218             if (ret < 0)
 219                 goto end;
 220         }
 221
 222         if (format) {
 223             ret = av_dict_set(&tee_slave->fifo_options, "fifo_format", format,
 224                               AV_DICT_DONT_STRDUP_VAL);
 225             format = NULL;
 226             if (ret < 0)
 227                 goto end;
 228         }
 229
 230         av_dict_free(&options);
 231         options = tee_slave->fifo_options;
 232         tee_slave->fifo_options = NULL;
 233     }
 234     ret = avformat_alloc_output_context2(&avf2, NULL,
 235                                          tee_slave->use_fifo ? "fifo" :format, filename);
 236     if (ret < 0)
 237         goto end;
 238     tee_slave->avf = avf2;
 239     av_dict_copy(&avf2->metadata, avf->metadata, 0);
 240     avf2->opaque   = avf->opaque;
 241     avf2->io_open  = avf->io_open;
 242     avf2->io_close2 = avf->io_close2;
 243     avf2->interrupt_callback = avf->interrupt_callback;
 244     avf2->flags = avf->flags;
 245     avf2->strict_std_compliance = avf->strict_std_compliance;
 246
 247     tee_slave->stream_map = av_calloc(avf->nb_streams, sizeof(*tee_slave->stream_map));
 248     if (!tee_slave->stream_map) {
 249         ret = AVERROR(ENOMEM);
 250         goto end;
 251     }
 252
 253     stream_count = 0;
 254     for (unsigned i = 0; i < avf->nb_streams; i++) {
 255         const AVStream *st = avf->streams[i];
 256         AVStream *st2;
 257         if (select) {
 258             tmp_select = av_strdup(select);  // av_strtok is destructive so we regenerate it in each loop
 259             if (!tmp_select) {
 260                 ret = AVERROR(ENOMEM);
 261                 goto end;
 262             }
 263             fullret = 0;
 264             first_subselect = tmp_select;
 265             next_subselect = NULL;
 266             while (subselect = av_strtok(first_subselect, slave_select_sep, &next_subselect)) {
 267                 first_subselect = NULL;
 268
 269                 ret = avformat_match_stream_specifier(avf, avf->streams[i], subselect);
 270                 if (ret < 0) {
 271                     av_log(avf, AV_LOG_ERROR,
 272                            "Invalid stream specifier '%s' for output '%s'\n",
 273                            subselect, slave);
 274                     goto end;
 275                 }
 276                 if (ret != 0) {
 277                     fullret = 1; // match
 278                     break;
 279                 }
 280             }
 281             av_freep(&tmp_select);
 282
 283             if (fullret == 0) { /* no match */
 284                 tee_slave->stream_map[i] = -1;
 285                 continue;
 286             }
 287         }
 288         tee_slave->stream_map[i] = stream_count++;
 289
 290         st2 = ff_stream_clone(avf2, st);
 291         if (!st2) {
 292             ret = AVERROR(ENOMEM);
 293             goto end;
 294         }
 295     }
 296
 297     ret = ff_format_output_open(avf2, filename, &options);
 298     if (ret < 0) {
 299         av_log(avf, AV_LOG_ERROR, "Slave '%s': error opening: %s\n", slave,
 300                av_err2str(ret));
 301         goto end;
 302     }
 303
 304     if ((ret = avformat_write_header(avf2, &options)) < 0) {
 305         av_log(avf, AV_LOG_ERROR, "Slave '%s': error writing header: %s\n",
 306                slave, av_err2str(ret));
 307         goto end;
 308     }
 309     tee_slave->header_written = 1;
 310
 311     tee_slave->bsfs = av_calloc(avf2->nb_streams, sizeof(*tee_slave->bsfs));
 312     if (!tee_slave->bsfs) {
 313         ret = AVERROR(ENOMEM);
 314         goto end;
 315     }
 316
 317     entry = NULL;
 318     while (entry = av_dict_iterate(bsf_options, NULL)) {
 319         const char *spec = entry->key;
 320         if (*spec) {
 321             if (strspn(spec, slave_bsfs_spec_sep) != 1) {
 322                 av_log(avf, AV_LOG_ERROR,
 323                        "Specifier separator in '%s' is '%c', but only characters '%s' "
 324                        "are allowed\n", entry->key, *spec, slave_bsfs_spec_sep);
 325                 ret = AVERROR(EINVAL);
 326                 goto end;
 327             }
 328             spec++; /* consume separator */
 329         }
 330
 331         for (unsigned i = 0; i < avf2->nb_streams; i++) {
 332             ret = avformat_match_stream_specifier(avf2, avf2->streams[i], spec);
 333             if (ret < 0) {
 334                 av_log(avf, AV_LOG_ERROR,
 335                        "Invalid stream specifier '%s' in bsfs option '%s' for slave "
 336                        "output '%s'\n", spec, entry->key, filename);
 337                 goto end;
 338             }
 339
 340             if (ret > 0) {
 341                 av_log(avf, AV_LOG_DEBUG, "spec:%s bsfs:%s matches stream %d of slave "
 342                        "output '%s'\n", spec, entry->value, i, filename);
 343                 if (tee_slave->bsfs[i]) {
 344                     av_log(avf, AV_LOG_WARNING,
 345                            "Duplicate bsfs specification associated to stream %d of slave "
 346                            "output '%s', filters will be ignored\n", i, filename);
 347                     continue;
 348                 }
 349                 ret = av_bsf_list_parse_str(entry->value, &tee_slave->bsfs[i]);
 350                 if (ret < 0) {
 351                     av_log(avf, AV_LOG_ERROR,
 352                            "Error parsing bitstream filter sequence '%s' associated to "
 353                            "stream %d of slave output '%s'\n", entry->value, i, filename);
 354                     goto end;
 355                 }
 356             }
 357         }
 358
 359         av_dict_set(&bsf_options, entry->key, NULL, 0);
 360     }
 361
 362     for (unsigned i = 0; i < avf->nb_streams; i++){
 363         int target_stream = tee_slave->stream_map[i];
 364         if (target_stream < 0)
 365             continue;
 366
 367         if (!tee_slave->bsfs[target_stream]) {
 368             /* Add pass-through bitstream filter */
 369             ret = av_bsf_get_null_filter(&tee_slave->bsfs[target_stream]);
 370             if (ret < 0) {
 371                 av_log(avf, AV_LOG_ERROR,
 372                        "Failed to create pass-through bitstream filter: %s\n",
 373                        av_err2str(ret));
 374                 goto end;
 375             }
 376         }
 377
 378         tee_slave->bsfs[target_stream]->time_base_in = avf->streams[i]->time_base;
 379         ret = avcodec_parameters_copy(tee_slave->bsfs[target_stream]->par_in,
 380                                       avf->streams[i]->codecpar);
 381         if (ret < 0)
 382             goto end;
 383
 384         ret = av_bsf_init(tee_slave->bsfs[target_stream]);
 385         if (ret < 0) {
 386             av_log(avf, AV_LOG_ERROR,
 387             "Failed to initialize bitstream filter(s): %s\n",
 388             av_err2str(ret));
 389             goto end;
 390         }
 391     }
 392
 393     if (options) {
 394         entry = NULL;
 395         while ((entry = av_dict_iterate(options, entry)))
 396             av_log(avf2, AV_LOG_ERROR, "Unknown option '%s'\n", entry->key);
 397         ret = AVERROR_OPTION_NOT_FOUND;
 398         goto end;
 399     }
 400
 401 end:
 402     av_free(format);
 403     av_free(select);
 404     av_dict_free(&options);
 405     av_dict_free(&bsf_options);
 406     av_freep(&tmp_select);
 407     return ret;
 408 }
 409
 410 static void log_slave(TeeSlave *slave, void *log_ctx, int log_level)
 411 {
 412     av_log(log_ctx, log_level, "filename:'%s' format:%s\n",
 413            slave->avf->url, slave->avf->oformat->name);
 414     for (unsigned i = 0; i < slave->avf->nb_streams; i++) {
 415         AVStream *st = slave->avf->streams[i];
 416         AVBSFContext *bsf = slave->bsfs[i];
 417         const char *bsf_name;
 418
 419         av_log(log_ctx, log_level, "    stream:%d codec:%s type:%s",
 420                i, avcodec_get_name(st->codecpar->codec_id),
 421                av_get_media_type_string(st->codecpar->codec_type));
 422
 423         bsf_name = bsf->filter->priv_class ?
 424                    bsf->filter->priv_class->item_name(bsf) : bsf->filter->name;
 425         av_log(log_ctx, log_level, " bsfs: %s\n", bsf_name);
 426     }
 427 }
 428
 429 static int tee_process_slave_failure(AVFormatContext *avf, unsigned slave_idx, int err_n)
 430 {
 431     TeeContext *tee = avf->priv_data;
 432     TeeSlave *tee_slave = &tee->slaves[slave_idx];
 433
 434     tee->nb_alive--;
 435
 436     close_slave(tee_slave);
 437
 438     if (!tee->nb_alive) {
 439         av_log(avf, AV_LOG_ERROR, "All tee outputs failed.\n");
 440         return err_n;
 441     } else if (tee_slave->on_fail == ON_SLAVE_FAILURE_ABORT) {
 442         av_log(avf, AV_LOG_ERROR, "Slave muxer #%u failed, aborting.\n", slave_idx);
 443         return err_n;
 444     } else {
 445         av_log(avf, AV_LOG_ERROR, "Slave muxer #%u failed: %s, continuing with %u/%u slaves.\n",
 446                slave_idx, av_err2str(err_n), tee->nb_alive, tee->nb_slaves);
 447         return 0;
 448     }
 449 }
 450
 451 static int tee_write_header(AVFormatContext *avf)
 452 {
 453     TeeContext *tee = avf->priv_data;
 454     unsigned nb_slaves = 0;
 455     const char *filename = avf->url;
 456     char **slaves = NULL;
 457     int ret;
 458
 459     while (*filename) {
 460         char *slave = av_get_token(&filename, slave_delim);
 461         if (!slave) {
 462             ret = AVERROR(ENOMEM);
 463             goto fail;
 464         }
 465         ret = av_dynarray_add_nofree(&slaves, &nb_slaves, slave);
 466         if (ret < 0) {
 467             av_free(slave);
 468             goto fail;
 469         }
 470         if (strspn(filename, slave_delim))
 471             filename++;
 472     }
 473
 474     if (!FF_ALLOCZ_TYPED_ARRAY(tee->slaves, nb_slaves)) {
 475         ret = AVERROR(ENOMEM);
 476         goto fail;
 477     }
 478     tee->nb_slaves = tee->nb_alive = nb_slaves;
 479
 480     for (unsigned i = 0; i < nb_slaves; i++) {
 481
 482         tee->slaves[i].use_fifo = tee->use_fifo;
 483         ret = av_dict_copy(&tee->slaves[i].fifo_options, tee->fifo_options, 0);
 484         if (ret < 0)
 485             goto fail;
 486
 487         if ((ret = open_slave(avf, slaves[i], &tee->slaves[i])) < 0) {
 488             ret = tee_process_slave_failure(avf, i, ret);
 489             if (ret < 0)
 490                 goto fail;
 491         } else {
 492             log_slave(&tee->slaves[i], avf, AV_LOG_VERBOSE);
 493         }
 494         av_freep(&slaves[i]);
 495     }
 496
 497     for (unsigned i = 0; i < avf->nb_streams; i++) {
 498         int mapped = 0;
 499         for (unsigned j = 0; j < tee->nb_slaves; j++)
 500             if (tee->slaves[j].avf)
 501                 mapped += tee->slaves[j].stream_map[i] >= 0;
 502         if (!mapped)
 503             av_log(avf, AV_LOG_WARNING, "Input stream #%d is not mapped "
 504                    "to any slave.\n", i);
 505     }
 506     av_free(slaves);
 507     return 0;
 508
 509 fail:
 510     for (unsigned i = 0; i < nb_slaves; i++)
 511         av_freep(&slaves[i]);
 512     close_slaves(avf);
 513     av_free(slaves);
 514     return ret;
 515 }
 516
 517 static int tee_write_trailer(AVFormatContext *avf)
 518 {
 519     TeeContext *tee = avf->priv_data;
 520     int ret_all = 0, ret;
 521
 522     for (unsigned i = 0; i < tee->nb_slaves; i++) {
 523         if ((ret = close_slave(&tee->slaves[i])) < 0) {
 524             ret = tee_process_slave_failure(avf, i, ret);
 525             if (!ret_all && ret < 0)
 526                 ret_all = ret;
 527         }
 528     }
 529     av_freep(&tee->slaves);
 530     return ret_all;
 531 }
 532
 533 static int tee_write_packet(AVFormatContext *avf, AVPacket *pkt)
 534 {
 535     TeeContext *tee = avf->priv_data;
 536     AVPacket *const pkt2 = ffformatcontext(avf)->pkt;
 537     int ret_all = 0, ret;
 538     unsigned s;
 539     int s2;
 540
 541     for (unsigned i = 0; i < tee->nb_slaves; i++) {
 542         AVFormatContext *avf2 = tee->slaves[i].avf;
 543         AVBSFContext *bsfs;
 544
 545         if (!avf2)
 546             continue;
 547
 548         /* Flush slave if pkt is NULL*/
 549         if (!pkt) {
 550             ret = av_interleaved_write_frame(avf2, NULL);
 551             if (ret < 0) {
 552                 ret = tee_process_slave_failure(avf, i, ret);
 553                 if (!ret_all && ret < 0)
 554                     ret_all = ret;
 555             }
 556             continue;
 557         }
 558
 559         s = pkt->stream_index;
 560         s2 = tee->slaves[i].stream_map[s];
 561         if (s2 < 0)
 562             continue;
 563
 564         if ((ret = av_packet_ref(pkt2, pkt)) < 0) {
 565             if (!ret_all)
 566                 ret_all = ret;
 567             continue;
 568         }
 569         bsfs = tee->slaves[i].bsfs[s2];
 570         pkt2->stream_index = s2;
 571
 572         ret = av_bsf_send_packet(bsfs, pkt2);
 573         if (ret < 0) {
 574             av_packet_unref(pkt2);
 575             av_log(avf, AV_LOG_ERROR, "Error while sending packet to bitstream filter: %s\n",
 576                    av_err2str(ret));
 577             ret = tee_process_slave_failure(avf, i, ret);
 578             if (!ret_all && ret < 0)
 579                 ret_all = ret;
 580         }
 581
 582         while(1) {
 583             ret = av_bsf_receive_packet(bsfs, pkt2);
 584             if (ret == AVERROR(EAGAIN)) {
 585                 ret = 0;
 586                 break;
 587             } else if (ret < 0) {
 588                 break;
 589             }
 590
 591             av_packet_rescale_ts(pkt2, bsfs->time_base_out,
 592                                  avf2->streams[s2]->time_base);
 593             ret = av_interleaved_write_frame(avf2, pkt2);
 594             if (ret < 0)
 595                 break;
 596         };
 597
 598         if (ret < 0) {
 599             ret = tee_process_slave_failure(avf, i, ret);
 600             if (!ret_all && ret < 0)
 601                 ret_all = ret;
 602         }
 603     }
 604     return ret_all;
 605 }
 606
 607 const FFOutputFormat ff_tee_muxer = {
 608     .p.name            = "tee",
 609     .p.long_name       = NULL_IF_CONFIG_SMALL("Multiple muxer tee"),
 610     .priv_data_size    = sizeof(TeeContext),
 611     .write_header      = tee_write_header,
 612     .write_trailer     = tee_write_trailer,
 613     .write_packet      = tee_write_packet,
 614     .p.priv_class      = &tee_muxer_class,
 615     .p.flags           = AVFMT_NOFILE | AVFMT_TS_NEGATIVE,
 616     .flags_internal    = FF_OFMT_FLAG_ALLOW_FLUSH,
 617 };