[MPlayer-cvslog] CVS: main/libmpcodecs ve_lavc.c,1.121,1.122

[Corey Hickey]

Michael Niedermayer wrote:
> ok, there are different macroblock types in b frames,
> 1. forward predicted ones, they use the previous non B frame
> 2. backward predicted ones, they use the next non B frame
> 3. bidirectional ones, they use 2 vectors, one pointing to the previous frame
>    one to the next
> 4. direct ones, they are like 3. except that they store only one vector and
>    calculate the second one from the colocated vector in the next non B frame
> (this is what mpeg4 supports, other standards are very similar)
> 
> now 1. 2. and 4. are the same from a motion estimation point of view, just
> find the best single vector using your favorite ME algorithm for P frames
> 3. has 2 vectors, previously we simply used the vectors from the forward
> and backward searches without refining them, now bidir_refine does a simple
> 4-dimensional diamond like search with the number affecting the shape of
> the used diamond, (larger number is slower)

Thanks for the explanation. I think that makes sense to me. Would the
following be appropriate for the man page?

bidir_refine=<0-4>
    Refine the two motion vectors used in biderectional macroblocks,
    rather than re-using vectors from the forward and backward searches.
    This option has no effect without B-frames.
       0    Disabled (default).
       1-4  Use a wider search (larger values are slower).


-Corey