You need to appreciate that any TV card is a 'low-resolution' device as far as the computer monitor display is concerned. To put a number to that, the underlying TV display is only 576 pixels high (for PAL standard).
So if, for example, you try to expand the TV display to make it full-screen on your (presumably) much higher resolution monitor, the TV display has to be scaled up considerably. This isn't so bad for still images and moving pictures - but makes it /very/ difficult to read moving text. It's a fact of life and nothing to do with your graphics card or monitor.(It's rather more techie than that, but hopefully that explanation will suffice).
You may find that the clarity of the rolling titles will improve considerably if (oddly) you /reduce/ the TV display window size so that it's the same as the original picture, i.e. 576 pixels high. Some TV card software actually gives a readout of the TV window size; our Hauppauge cards do so you may be in luck.
So if you tweak the windows size to be /exactly/ 768x576 pixels (PAL TV display), that's exactly 1:1 scaling when overlaid onto your monitor display, even though in a relatively small window, but will be the clearest you can get.
As an alternative, if you happen to have a very high-res monitor (e.g. 1600x1200), you could bump up the TV window to 1536x1152 pixels, when the scaling ratio is then /exactly/ 2:1. That also should maximise the clarity of the text.
Finally, if you need to catch a particular title screen, you can always take a snapshot which will give a still image of 768x576 pixels. HTH.