Adjust subpel refinement quality. This parameter controls qual-
ity versus speed tradeoffs involved in the motion estimation de-
cision process. subq=5 can compress up to 10% better than subq=1.
1 Runs fullpixel precision motion estimation on all candi-date macroblock types. Then selects the best type. Then refines the motion of that type to fast quarterpix-el precision (fastest).
2 Runs halfpixel precision motion estimation on all candi-date macroblock types. Then selects the best type. Then refines the motion of that type to fast quarterpix-el precision.
3 As 2, but uses a slower quarterpixel refinement.
4 Runs fast quarterpixel precision motion estimation on all candidate macroblock types. Then selects the best type. Then finishes the quarterpixel refinement for that type.
5 Runs best quality quarterpixel precision motion estima-tion on all candidate macroblock types, before selecting the best type (default).
6 Enables rate-distortion optimization of macroblock types in I- and P-frames.
7 Enables rate-distortion optimization of motion vectors and intra modes. (best)
In the above, "all candidates" does not exactly mean all enabled
types: 4x4, 4x8, 8x4 are tried only if 8x8 is better than 16x16.
