diff --git a/libavcodec/mpeg12.c b/libavcodec/mpeg12.c
index fde4e02..0ea14c6 100644
--- a/libavcodec/mpeg12.c
+++ b/libavcodec/mpeg12.c
@@ -112,7 +112,7 @@ static inline int mpeg1_decode_block_intra(MpegEncContext *s, DCTELEM *block, in
                 break;
             } else if (level != 0) {
                 i += run;
-                j = scantable[i];
+                j = scantable[i & 63];
                 level = (level * qscale * quant_matrix[j]) >> 4;
                 level = (level - 1) | 1;
                 level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
@@ -128,7 +128,7 @@ static inline int mpeg1_decode_block_intra(MpegEncContext *s, DCTELEM *block, in
                     level = SHOW_UBITS(re, &s->gb, 8)      ; LAST_SKIP_BITS(re, &s->gb, 8);
                 }
                 i += run;
-                j = scantable[i];
+                j = scantable[i & 63];
                 if (level < 0) {
                     level = -level;
                     level = (level * qscale * quant_matrix[j]) >> 4;
@@ -187,7 +187,7 @@ static inline int mpeg1_decode_block_inter(MpegEncContext *s, DCTELEM *block, in
 
             if (level != 0) {
                 i += run;
-                j = scantable[i];
+                j = scantable[i & 63];
                 level = ((level * 2 + 1) * qscale * quant_matrix[j]) >> 5;
                 level = (level - 1) | 1;
                 level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
@@ -203,7 +203,7 @@ static inline int mpeg1_decode_block_inter(MpegEncContext *s, DCTELEM *block, in
                     level = SHOW_UBITS(re, &s->gb, 8)      ; SKIP_BITS(re, &s->gb, 8);
                 }
                 i += run;
-                j = scantable[i];
+                j = scantable[i & 63];
                 if (level < 0) {
                     level = -level;
                     level = ((level * 2 + 1) * qscale * quant_matrix[j]) >> 5;
@@ -262,7 +262,7 @@ static inline int mpeg1_fast_decode_block_inter(MpegEncContext *s, DCTELEM *bloc
 
             if (level != 0) {
                 i += run;
-                j = scantable[i];
+                j = scantable[i & 63];
                 level = ((level * 2 + 1) * qscale) >> 1;
                 level = (level - 1) | 1;
                 level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
@@ -278,7 +278,7 @@ static inline int mpeg1_fast_decode_block_inter(MpegEncContext *s, DCTELEM *bloc
                     level = SHOW_UBITS(re, &s->gb, 8)      ; SKIP_BITS(re, &s->gb, 8);
                 }
                 i += run;
-                j = scantable[i];
+                j = scantable[i & 63];
                 if (level < 0) {
                     level = -level;
                     level = ((level * 2 + 1) * qscale) >> 1;
@@ -343,7 +343,7 @@ static inline int mpeg2_decode_block_non_intra(MpegEncContext *s, DCTELEM *block
 
             if (level != 0) {
                 i += run;
-                j = scantable[i];
+                j = scantable[i & 63];
                 level = ((level * 2 + 1) * qscale * quant_matrix[j]) >> 5;
                 level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
                 SKIP_BITS(re, &s->gb, 1);
@@ -354,7 +354,7 @@ static inline int mpeg2_decode_block_non_intra(MpegEncContext *s, DCTELEM *block
                 level = SHOW_SBITS(re, &s->gb, 12); SKIP_BITS(re, &s->gb, 12);
 
                 i += run;
-                j = scantable[i];
+                j = scantable[i & 63];
                 if (level < 0) {
                     level = ((-level * 2 + 1) * qscale * quant_matrix[j]) >> 5;
                     level = -level;
@@ -412,7 +412,7 @@ static inline int mpeg2_fast_decode_block_non_intra(MpegEncContext *s,
 
         if (level != 0) {
             i += run;
-            j  = scantable[i];
+            j  = scantable[i & 63];
             level = ((level * 2 + 1) * qscale) >> 1;
             level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
             SKIP_BITS(re, &s->gb, 1);
@@ -423,7 +423,7 @@ static inline int mpeg2_fast_decode_block_non_intra(MpegEncContext *s,
             level = SHOW_SBITS(re, &s->gb, 12); SKIP_BITS(re, &s->gb, 12);
 
             i += run;
-            j  = scantable[i];
+            j  = scantable[i & 63];
             if (level < 0) {
                 level = ((-level * 2 + 1) * qscale) >> 1;
                 level = -level;
@@ -489,7 +489,7 @@ static inline int mpeg2_decode_block_intra(MpegEncContext *s, DCTELEM *block, in
                 break;
             } else if (level != 0) {
                 i += run;
-                j  = scantable[i];
+                j  = scantable[i & 63];
                 level = (level * qscale * quant_matrix[j]) >> 4;
                 level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
                 LAST_SKIP_BITS(re, &s->gb, 1);
@@ -499,7 +499,7 @@ static inline int mpeg2_decode_block_intra(MpegEncContext *s, DCTELEM *block, in
                 UPDATE_CACHE(re, &s->gb);
                 level = SHOW_SBITS(re, &s->gb, 12); SKIP_BITS(re, &s->gb, 12);
                 i += run;
-                j  = scantable[i];
+                j  = scantable[i & 63];
                 if (level < 0) {
                     level = (-level * qscale * quant_matrix[j]) >> 4;
                     level = -level;
@@ -526,6 +526,7 @@ static inline int mpeg2_decode_block_intra(MpegEncContext *s, DCTELEM *block, in
 static inline int mpeg2_fast_decode_block_intra(MpegEncContext *s, DCTELEM *block, int n)
 {
     int level, dc, diff, j, run;
+    int i=0;
     int component;
     RLTable *rl;
     uint8_t * scantable = s->intra_scantable.permutated;
@@ -562,8 +563,8 @@ static inline int mpeg2_fast_decode_block_intra(MpegEncContext *s, DCTELEM *bloc
             if (level == 127) {
                 break;
             } else if (level != 0) {
-                scantable += run;
-                j = *scantable;
+                i += run;
+                j = scantable[i & 63];
                 level = (level * qscale * quant_matrix[j]) >> 4;
                 level = (level ^ SHOW_SBITS(re, &s->gb, 1)) - SHOW_SBITS(re, &s->gb, 1);
                 LAST_SKIP_BITS(re, &s->gb, 1);
@@ -572,8 +573,8 @@ static inline int mpeg2_fast_decode_block_intra(MpegEncContext *s, DCTELEM *bloc
                 run = SHOW_UBITS(re, &s->gb, 6) + 1; LAST_SKIP_BITS(re, &s->gb, 6);
                 UPDATE_CACHE(re, &s->gb);
                 level = SHOW_SBITS(re, &s->gb, 12); SKIP_BITS(re, &s->gb, 12);
-                scantable += run;
-                j = *scantable;
+                i += run;
+                j = scantable[ i & 63];
                 if (level < 0) {
                     level = (-level * qscale * quant_matrix[j]) >> 4;
                     level = -level;