#include <stdio.h>
#include <libavformat/avformat.h>
#include <libavutil/opt.h>
#include <libavutil/dict.h>

int main (int argc, char **argv) {
    AVFormatContext *fmt_ctx = NULL;
    AVDictionary** tags = NULL;
    AVDictionaryEntry *tag = NULL;
    int ret;
    char err_msg[1024];

    if (argc != 2) {
        printf("usage: %s <input_file>\n"
               "example program to demonstrate the use of the libavformat metadata API.\n"
               "\n", argv[0]);
        return 1;
    }

    av_register_all();

    ret = avformat_open_input(&fmt_ctx, argv[1], NULL, NULL);
    if (ret != 0) {
        printf("%s", av_err2str(ret));
        return ret;  // fails here
    }

    printf("Opened file.\n");

    ret = av_opt_get_dict_val(fmt_ctx, "metadata", AV_OPT_SEARCH_CHILDREN, tags);
    if (ret != 0) {
        printf("%s", av_err2str(ret));
        return ret;  // fails here
    }

    printf("Copied metadata\n");

    while ((tag = av_dict_get(*tags, "", tag, AV_DICT_IGNORE_SUFFIX)))
        printf("%s=%s\n", tag->key, tag->value);

    avformat_close_input(&fmt_ctx);
    return 0;
}