fix seek() with no previous frame displayed allow stepping forwards through a video source frame by frame
fix seek() with no previous frame displayed
allow stepping forwards through a video source frame by frame


git-svn-id: d4fdfcd4de20a449196f78acc655f735742cd30d@2522 14d46d22-621c-0410-bb3d-6f67920f7d95

regular/pyglet-avbin-optimizations,regular/pyglet-avbin-optimizations,regular/pyglet-avbin-optimizations,regular/pyglet-avbin-optimizations