Update safety check as the maximum pixel size is no longer 4.

New max size is 16bit * 4 samples (RGBA).

Originally committed as revision 18655 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/utils.c

@@ -200,7 +200,7 @@ void avcodec_align_dimensions(AVCodecContext *s, int *width, int *height){
 }
 
 int avcodec_check_dimensions(void *av_log_ctx, unsigned int w, unsigned int h){
-    if((int)w>0 && (int)h>0 && (w+128)*(uint64_t)(h+128) < INT_MAX/4)
+    if((int)w>0 && (int)h>0 && (w+128)*(uint64_t)(h+128) < INT_MAX/8)
         return 0;
 
     av_log(av_log_ctx, AV_LOG_ERROR, "picture size invalid (%ux%u)\n", w, h);