fix video-image request, zoom before video start.

diff --git a/gtk2_ardour/video_timeline.cc b/gtk2_ardour/video_timeline.cc
index eed09fdb23d24c8226feaab15c5afaedc778d45f..a1dd4bcfbbc89edaa03078c2886e3c7798703ed9 100644 (file)
--- a/gtk2_ardour/video_timeline.cc
+++ b/gtk2_ardour/video_timeline.cc
@@ -356,16 +356,20 @@ VideoTimeLine::update_video_timeline()
        vtl_start -= visible_video_frames * vtl_dist;
        visible_video_frames *=3;
 
-       if (vtl_start < video_offset ) {
-               visible_video_frames += ceil((double)vtl_start/vtl_dist);
+       /* don't request frames that are too far to the right */
+       if (vtl_start < video_offset) {
+               visible_video_frames = std::max((double)0.0, (double)visible_video_frames + ceil((double)(vtl_start - video_offset)/vtl_dist));
                vtl_start = video_offset;
        }
 
-       /* apply video-file constraints */
+       /* apply video-file constraints
+        * (first frame in video is at video_start_offset) */
        if (vtl_start > video_start_offset + video_duration + video_offset ) {
                visible_video_frames = 0;
        }
-       /* TODO optimize: compute rather than iterate */
+       /* trim end.
+        * end = position on timeline (video-offset)  minus  video-file's first frame position
+        * TODO optimize: compute rather than iterate */
        while (visible_video_frames > 0 && vtl_start + (visible_video_frames-1) * vtl_dist >= video_start_offset + video_duration + video_offset) {
                --visible_video_frames;
        }