I have tried to get a proper video-output for TV via nvtv but the problem is the size of the output picture. When I am using the fullscreen in video player the TV shows only 1/4-1/3 of the whole screen this is of course because the desktop resolution is 1280x1024 and TV much less. Is there some option or method to grap whole screen and downscale it to the TV?

One possibility could also be to use low-resolution fullscreenmode but this doesn't seem to be possible in VLC or MPlayer for example.