On 8 Apr 2008, at 16:43, Ian Bates wrote:

What I would like is to maintain the stream 16:9 ratio but by by cropping the left and right sections of the stream that fall 'outside' the TV, so the full real estate of the TV is used, at the expense of losing some stream information.

This setting is most often called crop mode. The specific setting you're after is often called pan-and-scan.

I can't say how to achieve the desired output with xineliboutput though, since I use softdevice.