Thanks for your support @crackwitz.
Sorry, but maybe I did not understand correctly you suggestion.
Your answer means that opencv is using the video libraries: gstreamer or ffmpeg and I should test my stream in a program which use these libraries, right?
Is not that exactly what I did in my print screen above, when I compare VLC to opencv, same time, same camera? I showed the stream running perfectly in VLC and grayscreen in opencv.
Sorry about misunderstanding. I wait for your support.
Thanks and best regards.