These are granular controls to optimize the quality of your outputs, for users who want to tightly control the methods used for partitioning and motion estimation. The vast majority of users do not need to override the optimized defaults.
Specify the combinations of inter and intra partitions.
+partp8x8, +partp4x4, +partb8x8, +parti8x8, +parti4x4
This allows B-frames to use weighted prediction options other than the default. There is no real speed cost for this, so it should always be enabled.
+bpyramid, +wpred, +mixed_refs, +dct8×8, -fastpskip/+fastpskip, –no-fast-pskip/nothing, +aud.
Specify the motion estimation method to method.
epzs, hex, umh, full
Specify the maximum range of motion search.
Specify which algorithms are used for both subpixel motion searching and partition decision.
1: Fastest, but extremely low quality. Should be avoided except on first pass encoding.
2-5: Progressively better and slower, 5 serves as a good medium for higher speed encoding.
8-9: Activates rate-distortion refinement, which uses RDO to refine both motion vectors and intra prediction modes. Slower than subme 6, but again, more efficient.
Specify the optimal rounding choices for the maximum rate-distortion score, to maximize PSNR relative to bitrate.
0, 1, 2