static int opt_streamid(const char *opt, const char *arg)
{
    int idx;
    char *p;
    char idx_str[16];

    av_strlcpy(idx_str, arg, sizeof(idx_str));
    p = strchr(idx_str, ':');
    if (!p) {
        fprintf(stderr,
                "Invalid value '%s' for option '%s', required syntax is 'index:value'\n",
                arg, opt);
        ffmpeg_exit(1);
    }
    *p++ = '\0';
    idx = parse_number_or_die(opt, idx_str, OPT_INT, 0, INT_MAX);
    streamid_map = grow_array(streamid_map, sizeof(*streamid_map), &nb_streamid_map, idx+1);
    streamid_map[idx] = parse_number_or_die(opt, p, OPT_INT, 0, INT_MAX);
    return 0;
}