public static extern void avfilter_free(AVFilterContext* filter);
 public static extern int avfilter_insert_filter(AVFilterLink* link, AVFilterContext* filt, int filt_srcpad_idx, int filt_dstpad_idx);
 public static extern int avfilter_init_filter(AVFilterContext* filter, String args, void* opaque);
 public static extern int avfilter_open(AVFilterContext** filter_ctx, AVFilter* filter, String inst_name);
 public static extern int avfilter_process_command(AVFilterContext* filter, String cmd, String arg, String res, int res_len, int flags);
 public static extern int avfilter_config_links(AVFilterContext* filter);
 public static extern int avfilter_link(AVFilterContext* src, int srcpad, AVFilterContext* dst, int dstpad);