Added frame offset slider to clip datablocks

In contrast to start_frame (which affects on where footage actually
starts to play and also affects on all data associated with a clip
such as motion tracking, reconstruction and so on) this slider only
affects on a way how frame number is mapping to a filename, without
touching any kind of tracking data.

The formula is:
  file_name = clip_file_name + frame_offset - (start_frame - 1)

1 files changed, 8 insertions, 1 deletions

diff --git a/source/blender/makesdna/DNA_movieclip_types.h b/source/blender/makesdna/DNA_movieclip_types.h
index 19004dbc8b8..d8bba4a3bf5 100644
--- a/source/blender/makesdna/DNA_movieclip_types.h
+++ b/source/blender/makesdna/DNA_movieclip_types.h
@@ -86,7 +86,14 @@ typedef struct MovieClip {
 
 	int len;    /* length of movie */
 
-	int start_frame, pad;
+	int start_frame;    /* scene frame number footage starts playing at */
+	                    /* affects all data which is associated with a clip */
+	                    /* such as motion tracking, camera reconstruciton and so */
+
+	int frame_offset;   /* offset which is adding to a file number when reading frame */
+	                    /* from a file. affects only a way how scene frame is mapping */
+	                    /* to a file name and not touches other data associated with */
+	                    /* a clip */
 } MovieClip;
 
 typedef struct MovieClipScopes {