ffmpeg.c（4.3.1）源码剖析（二）

int main_ffmpeg431(int argc, char **argv)
{
    int i, ret;
    BenchmarkTimeStamps ti;
    init_dynload();
    register_exit(ffmpeg_cleanup);
    setvbuf(stderr,NULL,_IONBF,0); /* win32 runtime needs this */
    av_log_set_flags(AV_LOG_SKIP_REPEATED);
    parse_loglevel(argc, argv, options);
    if(argc>1 && !strcmp(argv[1], "-d")){
        run_as_daemon=1;
        av_log_set_callback(log_callback_null);
        argc--;
        argv++;
    }
#if CONFIG_AVDEVICE
    avdevice_register_all();
#endif
    avformat_network_init();
    //show_banner(argc, argv, options);
    /* parse options and open all input/output files */
    ret = ffmpeg_parse_options(argc, argv);
    if (ret < 0)
        exit_program(1);
    if (nb_output_files <= 0 && nb_input_files == 0) {
        show_usage();
        av_log(NULL, AV_LOG_WARNING, "Use -h to get full help or, even better, run 'man %s'\n", program_name);
        exit_program(1);
    }
    /* file converter / grab */
    if (nb_output_files <= 0) {
        av_log(NULL, AV_LOG_FATAL, "At least one output file must be specified\n");
        exit_program(1);
    }
    for (i = 0; i < nb_output_files; i++) {
        if (strcmp(output_files[i]->ctx->oformat->name, "rtp"))
            want_sdp = 0;
    }
    current_time = ti = get_benchmark_time_stamps();
    if (transcode() < 0)
        exit_program(1);
    if (do_benchmark) {
        int64_t utime, stime, rtime;
        current_time = get_benchmark_time_stamps();
        utime = current_time.user_usec - ti.user_usec;
        stime = current_time.sys_usec  - ti.sys_usec;
        rtime = current_time.real_usec - ti.real_usec;
        av_log(NULL, AV_LOG_INFO,
               "bench: utime=%0.3fs stime=%0.3fs rtime=%0.3fs\n",
               utime / 1000000.0, stime / 1000000.0, rtime / 1000000.0);
    }
    av_log(NULL, AV_LOG_DEBUG, "%"PRIu64" frames successfully decoded, %"PRIu64" decoding errors\n",
           decode_error_stat[0], decode_error_stat[1]);
    if ((decode_error_stat[0] + decode_error_stat[1]) * max_error_rate < decode_error_stat[1])
        exit_program(69);
    exit_program(received_nb_signals ? 255 : main_return_code);
    return main_return_code;
}

ffmpeg -i abc.mp4 -i bbb.avi -vcodec libx264 -acodec aac -vf scale=640:480 -f flv -y abc.flv

/**
 * Split the commandline into an intermediate form convenient for further
 * processing.
 *
 * The commandline is assumed to be composed of options which either belong to a
 * group (those with OPT_SPEC, OPT_OFFSET or OPT_PERFILE) or are global
 * (everything else).
 *
 * A group (defined by an OptionGroupDef struct) is a sequence of options
 * terminated by either a group separator option (e.g. -i) or a parameter that
 * is not an option (doesn't start with -). A group without a separator option
 * must always be first in the supplied groups list.
 *
 * All options within the same group are stored in one OptionGroup struct in an
 * OptionGroupList, all groups with the same group definition are stored in one
 * OptionGroupList in OptionParseContext.groups. The order of group lists is the
 * same as the order of group definitions.
 */
int split_commandline(OptionParseContext *octx, int argc, char *argv[],
                      const OptionDef *options,
                      const OptionGroupDef *groups, int nb_groups);

/**
 * Parse an options group and write results into optctx.
 *
 * @param optctx an app-specific options context. NULL for global options group
 */
int parse_optgroup(void *optctx, OptionGroup *g);

#define MATCH_PER_STREAM_OPT(name, type, outvar, fmtctx, st)\
{\
    int i, ret, matches = 0;\
    SpecifierOpt *so = NULL;\
    for (i = 0; i < o->nb_ ## name; i++) {\
        char *spec = o->name[i].specifier;\
        if ((ret = check_stream_specifier(fmtctx, st, spec)) > 0) {\
            outvar = o->name[i].u.type;\
            so = &o->name[i];\
            matches++;\
        } else if (ret < 0)\
            exit_program(1);\
    }\
    if (matches > 1)\
       WARN_MULTIPLE_OPT_USAGE(name, type, so, st);\
}
#define MATCH_PER_TYPE_OPT(name, type, outvar, fmtctx, mediatype)\
{\
    int i;\
    for (i = 0; i < o->nb_ ## name; i++) {\
        char *spec = o->name[i].specifier;\
        if (!strcmp(spec, mediatype))\
            outvar = o->name[i].u.type;\
    }\
}

/**
 * Add a graph described by a string to a graph.
 *
 * @param[in]  graph   the filter graph where to link the parsed graph context
 * @param[in]  filters string to be parsed
 * @param[out] inputs  a linked list of all free (unlinked) inputs of the
 *                     parsed graph will be returned here. It is to be freed
 *                     by the caller using avfilter_inout_free().
 * @param[out] outputs a linked list of all free (unlinked) outputs of the
 *                     parsed graph will be returned here. It is to be freed by the
 *                     caller using avfilter_inout_free().
 * @return zero on success, a negative AVERROR code on error
 *
 * @note This function returns the inputs and outputs that are left
 * unlinked after parsing the graph and the caller then deals with
 * them.
 * @note This function makes no reference whatsoever to already
 * existing parts of the graph and the inputs parameter will on return
 * contain inputs of the newly parsed part of the graph.  Analogously
 * the outputs parameter will contain outputs of the newly created
 * filters.
 */
int avfilter_graph_parse2(AVFilterGraph *graph, const char *filters,
                          AVFilterInOut **inputs,
                          AVFilterInOut **outputs);