add_vf_pp_stage
err = add_vf_pp_stage(pipe, in_frame, vf_frame, vf_pp_binary,
err = add_vf_pp_stage(pipe, in_frame, out_frame, vf_pp_binary,
err = add_vf_pp_stage(pipe, in_frame,
err = add_vf_pp_stage(pipe, in_frame, vf_frame[0],
err = add_vf_pp_stage(pipe, in_frame, vf_frame, vf_pp_binary,