check mb/me_threshold range, fixes assertion failure

Originally committed as revision 4082 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/motion_est.c

@@ -1016,7 +1016,7 @@ static inline int check_input_motion(MpegEncContext * s, int mb_x, int mb_y, int
     
     if(p_type && USES_LIST(mb_type, 1)){
         av_log(c->avctx, AV_LOG_ERROR, "backward motion vector in P frame\n");
-        return INT_MAX/4;
+        return INT_MAX/2;
     }
     assert(IS_INTRA(mb_type) || USES_LIST(mb_type,0) || USES_LIST(mb_type,1));
     
@@ -1034,7 +1034,7 @@ static inline int check_input_motion(MpegEncContext * s, int mb_x, int mb_y, int
         
         if(!(s->flags & CODEC_FLAG_INTERLACED_ME)){
             av_log(c->avctx, AV_LOG_ERROR, "Interlaced macroblock selected but interlaced motion estimation disabled\n");
-            return INT_MAX/4;
+            return INT_MAX/2;
         }
 
         if(USES_LIST(mb_type, 0)){
@@ -1095,7 +1095,7 @@ static inline int check_input_motion(MpegEncContext * s, int mb_x, int mb_y, int
     }else if(IS_8X8(mb_type)){
         if(!(s->flags & CODEC_FLAG_4MV)){
             av_log(c->avctx, AV_LOG_ERROR, "4MV macroblock selected but 4MV encoding disabled\n");
-            return INT_MAX/4;
+            return INT_MAX/2;
         }
         cmpf= s->dsp.sse[1];
         chroma_cmpf= s->dsp.sse[1];

libavcodec/mpegvideo.c

@@ -1054,6 +1054,16 @@ int MPV_encode_init(AVCodecContext *avctx)
         av_log(avctx, AV_LOG_ERROR, "framerate not set\n");
         return -1;
     }
+    
+    i= (INT_MAX/2+128)>>8;
+    if(avctx->me_threshold >= i){
+        av_log(avctx, AV_LOG_ERROR, "me_threshold too large, max is %d\n", i - 1);
+        return -1;
+    }
+    if(avctx->mb_threshold >= i){
+        av_log(avctx, AV_LOG_ERROR, "mb_threshold too large, max is %d\n", i - 1);
+        return -1;
+    }
         
     i= ff_gcd(avctx->frame_rate, avctx->frame_rate_base);
     if(i > 1){