Fast first pass mode. During the first pass of a two or more pass
encode it is possible to gain speed by disabling some op-
tions with negligible or even no impact on the final pass output
quality.
0 disabled (default)
1 Reduce subq, frameref and disable some inter-macroblock
partition analysis modes.
2 Reduce subq and frameref to 1, use a diamond ME search
and disable all partition analysis modes.
Level 1 can increase first pass speed up to 2x with no change in
the global PSNR of the final pass compared to a full quality
first pass.
Level 2 can increase first pass speed up to 4x with about +/-
0.05dB change in the global PSNR of the final pass compared to a
full quality first pass.
