         for ob in @objects
             # TODO: optimize
             affected_channels = {}
-            for strip in ob.animation_strips
+            for strip in ob.animation_strips when strip in @strips
                 {frame_start, frame_end, action_frame_start, action_frame_end} = strip
                 strip_pos = @pos - frame_start
                 strip_pos_reverse = frame_end - @pos

        # - members usually assigned in step()
        # - members used in apply()
        # - methods for regular usage, that can be chained
        {exclude=[], start_marker, end_marker} = options or {}
        full_exclude_list = []
        for thing in exclude
            if thing.length?

        @_index = -1

    has_strips: ->
        @strips.length != 0

    debug_strip_filters: ->
        for ob in @objects
            for strip in ob.animation_strips
                console.log @_strip_name_filter, strip.name, @_strip_name_filter.test (strip.name or '')
        return

    play: ->
        if not @playing
