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, 5 insertions, 1 deletions

diff --git a/source/blender/editors/space_clip/clip_ops.c b/source/blender/editors/space_clip/clip_ops.c
index b53cf027c78..1938cd7b53d 100644
--- a/source/blender/editors/space_clip/clip_ops.c
+++ b/source/blender/editors/space_clip/clip_ops.c
@@ -40,6 +40,7 @@
 #include "BLI_path_util.h"
 #include "BLI_math.h"
 #include "BLI_rect.h"
+#include "BLI_threads.h"
 
 #include "BLF_translation.h"
 
@@ -1004,8 +1005,11 @@ static void proxy_startjob(void *pjv, short *stop, short *do_update, float *prog
 		}
 	}
 
-	if (build_undistort_count)
+	if (build_undistort_count) {
+		int threads = BLI_system_thread_count();
 		distortion = BKE_tracking_distortion_new();
+		BKE_tracking_distortion_set_threads(distortion, threads);
+	}
 
 	for (cfra = sfra; cfra <= efra; cfra++) {
 		if (clip->source != MCLIP_SRC_MOVIE)