av_read_frame（）方法的输入参数

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.I want to read and open a video in encoded doma