Small tasks #2 (Iterative motion estimation)
FFmpeg supports iterative motion estimation, but only for snow. It would be interresting to implement/port this code to the generic mpeg framework (motion_est.c/mpegvideo.c/h) in ffmpeg
This task requires:
- Reading and understanding the generic motion estimation code
- Reading and understanding the iterative motion estimation code in snow.c
- Porting/Implementing iterative ME for the generic code
The advantage of iterative ME is higher quality per bitrate (but at higher computational cost).
Normal motion estimation tries to optimize each motion vector so as to minimize the weighted sum of the distortion (difference to the input picture) and the rate (bits for the motion vector). And after doing that for vector i, its done with i+1, then i+2 and so on, where all past vectors are held constant and all future ones are ignored. This is of course not correct, iterative motion estimation OTOH does not ignore any vectors but rather considers the bits of the future vectors too and performs several passes over all blocks until no further improvement is achived (=the search found a local minimum)