Multi-threaded frame calculation for movie clip proxies

This commit implements multi-threaded calculation of frames
when building proxies. Both scaling and undistortion steps
are now threaded.

Frames and proxy resolution are still handled one-by-one,
saving files after every single step. So if HDD is not so
fast, this commit could have not so much benefit.

Internal changes:

- Added IMB_scaleImBuf_threaded which scales given image
  buffer in multiple threads and uses bilinear filtering.

- libmv's camera intrinsics now have SetThreads() method
  which is used to specify how many OpenMP threads to use
  for buffer distortion/undistortion.

  And yeah, this code is using OpenMP for threading.

- Reshuffled a bit libmv-capi calls and added function
  BKE_tracking_distortion_set_threads to specify number
  of threads used by intrinscis.

1 files changed, 1 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_tracking.h b/source/blender/blenkernel/BKE_tracking.h
index ebf29fde8ee..c8ad708f832 100644
--- a/source/blender/blenkernel/BKE_tracking.h
+++ b/source/blender/blenkernel/BKE_tracking.h
@@ -144,6 +144,7 @@ void BKE_tracking_camera_get_reconstructed_interpolate(struct MovieTracking *tra
 struct MovieDistortion *BKE_tracking_distortion_new(void);
 void BKE_tracking_distortion_update(struct MovieDistortion *distortion, struct MovieTracking *tracking,
                                     int calibration_width, int calibration_height);
+void BKE_tracking_distortion_set_threads(struct MovieDistortion *distortion, int threads);
 struct MovieDistortion *BKE_tracking_distortion_copy(struct MovieDistortion *distortion);
 struct ImBuf *BKE_tracking_distortion_exec(struct MovieDistortion *distortion, struct MovieTracking *tracking,
                                            struct ImBuf *ibuf, int width, int height, float overscan, int undistort);