I'd like to say its easy, but its rocket science. In fact, since the shuttle astronauts tried to watch a dvd on a computer a few months back and even with NASA's assistance was unable to get it to play, I guess even rocket scientists cant figure out some parts of it!
High def tuner card in my htpc. I dont get all the channels because of a big ridge, but I get a few.
Capture the mpeg 2 stream from the tuner card. Convert the mpeg2 to mpeg4 with a high enough bitrate to maintain the same PQ as the mpeg2 stream. Stream the mpeg4 to a client with media player classic. Use a vista sidebar app to measure network throughput. Compare that to the network throughput used with directv2pc.
While directv may be using the same encoders as Sky, saying they'll produce the same results is like saying two cars both have v-8 engines, so they'll go the same speed.
H.264 encoders have a brazillion options for optimizing picture quality or bandwidth utilization, but unless you're prepared to use a lot of bandwidth you generally have to make compromises. Some will be hard to identify with the naked eye without looking for particular things. Some become quite obvious in high motion scenes, transition scenes, very dark or very light scenes, etc.
These particular encoders have at least 3 different default settings for 1080i. The difference in bandwidth needed for the highest quality of those settings is about 2.5x that of the lowest quality setting.