My movie clip contains other movie clips at the moment
If your movieclip contains other movieclips which are triggered with actionscript this method will not work.
You will have to seperate this movielip from you main file, create a swf and convert the swf with a swf2video converter or export it as Quicktime/animation.
We write blitting scripts(AIR) that essentially frame capture to create sequences or sprite sheets (RGBA32 png no problem)
the only downside is you need to author a definitive start -> end to define the number of frames you want.
if you nest a Bird flap with 5 frames clips inside a 6 frame hop then the clip will only loop perffectly if you author 30 frames...
if you want to make it exactly 6 frames without skipping you need to manually unify these motions
There is sprite packing software (such as texture packer) which will blit a swf [movieClip]; I author traditional 2D vFX in flash, add some blur/glow and other tween FX such as advanced color/alpha changes. (make sure the timelines are unified) Bring the swf to Texturepacker and the thing blits out the sprite sheet wonderfully with all the movieClip filter FX.
too bad the native flash software can't do this. in order to do it in flash you have to use graphic symbols. therefore the timelines must show you the animation and what you see is what you get. And since they have to be graphics you don't get any movieclip filters blur/glow . dissapointing