c++ - av_read_frame() 方法的输入参数

Question

我想在不解码的情况下在编码域中读取和打开视频。到目前为止，我已经编写了代码，并且它可以正常工作。但是方法 av_read_frame() 的输出只是给出了零的数量，并且相同的负整数值正在重复。
我不确定我是否将参数正确传递给了方法。请帮忙。

void CFfmpegmethods::VideoRead(){
av_register_all();

    const char *url = "H:\\Sanduni_projects\\ad_1.mp4";
    AVDictionary *options = NULL;
    AVFormatContext *s = avformat_alloc_context(); //NULL;
    //AVFormatContext *avfmt = NULL;
    //avformat_alloc_context();

    AVPacket pkt;

    //AVFormatContext *avformat_alloc_context();
    //AVIOContext *avio_alloc_context();

    //open an input stream and read the header
    int ret = avformat_open_input(&s, url, NULL, NULL); 

    //avformat_find_stream_info(s, &options); //finding the missing information 

    if (ret < 0)
        abort();

    av_dict_set(&options, "video_size", "640x480", 0);
    av_dict_set(&options, "pixel_format", "rgb24", 0);

    if (avformat_open_input(&s, url, NULL, &options) < 0){
        abort();
    }

    av_dict_free(&options);

    AVDictionaryEntry *e;

    if (e = av_dict_get(options, "", NULL, AV_DICT_IGNORE_SUFFIX)) {
        fprintf(stderr, "Option %s not recognized by the demuxer.\n", e->key);
        abort();
    }
    //int i = 0;
    while (1){
        //Split what is stored in the file into frames and return one for each call
        //returns the next frame of the stream
        int frame = av_read_frame(s, &pkt);
        //cout <<i << " " << frame << endl;
        waitKey(30);
        //i++;
    }

    //make the packet free
    av_packet_unref(&pkt);

    //Close the file after reading
    avformat_close_input(&s);

}

Answer 1

方法 av_read_frame() 在读取数据包时输出零，然后给出负值。在我的代码循环中无限运行。因此给出无限数量的负值。