input parameters for av_read_frame() method - c++

Question

I want to read and open a video in encoded domain without decoding. I have written the code up to now and it works without errors. But the output of the method av_read_frame() just gives number of zeros and same negative integer value is repeating.
I'm not sure whether I passed the parameters correctly to the method. Please help.
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

Method av_read_frame() output zeros while reading the packets and after that gives negative values. In my code loop runs infinitely. Therefore gives infinite number of negative values.

Answer 2

This is the modified code
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);
duration = pkt->duration;
size = pkt->size;
total_size = total_size + size;
total_duration = total_duration + duration;
i++;
if (frame < 0) break;
cout << "frame" << i << " " << size << " "<< duration << endl;
}