fixed multiple allocation bug

Originally committed as revision 675 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/msmpeg4.c

@@ -760,9 +760,14 @@ static void init_h263_dc_for_msmpeg4(void)
 /* init all vlc decoding tables */
 int msmpeg4_decode_init_vlc(MpegEncContext *s)
 {
+    static int done = 0;
     int i;
     MVTable *mv;
 
+
+    if (!done) {
+        done = 1;
+
         for(i=0;i<NB_RL_TABLES;i++) {
             init_rl(&rl_table[i]);
             init_vlc_rl(&rl_table[i]);
@@ -821,7 +826,7 @@ int msmpeg4_decode_init_vlc(MpegEncContext *s)
         init_vlc(&v1_inter_cbpc_vlc, 6, 25, 
                  inter_MCBPC_bits, 1, 1,
                  inter_MCBPC_code, 1, 1);
-
+    }
     return 0;
 }