I can only get it working some of the time, but when I did, I triple checked that it saved 2 pixels every 8 frames. (1,2,1,2,1,2,2,3 instead of 1,2,1,2,1,2,1,2) I could be wrong. counting pixels is a difficult task.
I got that wrong, I counted the pixels wrong three times.
Address A202 is maro's speed, and is only measured in pixels. There are no subpixels.
It turns out that the pixel trick has nothing to do with ducking, only slowing down, and your normal oscilation (1,2,1,2,1,2,1,2) is considered faster than this oscilation (1,2,1,2,2,1,1,2) even though they are exatly the same overall. Slowing down slightly, by pressing backwards or ducking and sliding will put you into this oscilation, and pressing forward again will bring you to the normal oscilation. you will notice that the "slower" oscilation has two 2's adjacent to each other. By swithching between the "slow" oscilation and the "fast" ones at the right time, we gain a pixel.
Pressing backwards for 2 frames, forwards for 4 frames backwards for 2 and forwards for 6 frames is, as far as I know the fastest method of travel on the ground. This is very hard to do as it only works sometimes, and with very specific setups (meaning, I have done it once and have never been able to do it again). The pixel trick can also be used in the air as well.
EDITAGAIN: you can now use the pixel trick in the air. watch this short demonstration video to see how.
it's 3 frames backwards, 1 frame forwards, 1 frame backwards, 3 frames forwards. repeat.
http://dehacked.2y.net/microstorage.php/info/796437324/omgf.vbm
I couldn't figure out how to land and do the pixel trick on the ground without losing any time, so i guess if you start jumping, you can't stop until the end of the level. This is probably going to make the next SML2 run much less entertaining with all the spazzing.