VSE: Improved Retiming system

Patch implements better way to control playback speed than it is
possible to do with speed effect. Speed factor property can be set in
Time panel.

There are 2 layers of control:

Option to retime movie to match scene FPS rate.
Custom speed factor to control playback rate.
Since playback rate is strip property, it is now possible to manipulate
strip as normal one even if it is retimed.

To facilitate manipulation, some functions need to consider speed factor
and apply necessary corrections to strip offset or strip start. These
corrections may need to be float numbers, so start and offsets must be
float as well.

Sound strips now use speed factor instead of pitch. This means, that
strips will change length to match usable length. In addition, it is
possible to group movie and sound strip and change speed of meta strip.

1 files changed, 9 insertions, 4 deletions

diff --git a/source/blender/sequencer/SEQ_render.h b/source/blender/sequencer/SEQ_render.h
index a74eba5fc6f..9c163de4230 100644
--- a/source/blender/sequencer/SEQ_render.h
+++ b/source/blender/sequencer/SEQ_render.h
@@ -79,20 +79,23 @@ struct ImBuf *SEQ_get_thumbnail(const struct SeqRenderData *context,
 /**
  * Get frame for first thumbnail.
  */
-float SEQ_render_thumbnail_first_frame_get(struct Sequence *seq,
+float SEQ_render_thumbnail_first_frame_get(const struct Scene *scene,
+                                           struct Sequence *seq,
                                            float frame_step,
                                            struct rctf *view_area);
 /**
  * Get frame for first thumbnail.
  */
-float SEQ_render_thumbnail_next_frame_get(struct Sequence *seq,
+float SEQ_render_thumbnail_next_frame_get(const struct Scene *scene,
+                                          struct Sequence *seq,
                                           float last_frame,
                                           float frame_step);
 /**
  * Get frame step for equally spaced thumbnails. These thumbnails should always be present in
  * memory, so they can be used when zooming.
  */
-int SEQ_render_thumbnails_guaranteed_set_frame_step_get(const struct Sequence *seq);
+int SEQ_render_thumbnails_guaranteed_set_frame_step_get(const struct Scene *scene,
+                                                        const struct Sequence *seq);
 /**
  * Render set of evenly spaced thumbnails that are drawn when zooming..
  */
@@ -112,7 +115,9 @@ void SEQ_render_new_render_data(struct Main *bmain,
                                 int for_render,
                                 SeqRenderData *r_context);
 int SEQ_render_evaluate_frame(struct ListBase *seqbase, int timeline_frame);
-struct StripElem *SEQ_render_give_stripelem(struct Sequence *seq, int timeline_frame);
+struct StripElem *SEQ_render_give_stripelem(const struct Scene *scene,
+                                            struct Sequence *seq,
+                                            int timeline_frame);
 
 void SEQ_render_imbuf_from_sequencer_space(struct Scene *scene, struct ImBuf *ibuf);
 void SEQ_render_pixel_from_sequencer_space_v4(struct Scene *scene, float pixel[4]);