avcodec/mjpegdec: Do not permute quantization tables

This fixes issues if the permutation changes, as quantizations tables would need to be reread
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/mjpegdec.c

@@ -166,7 +166,7 @@ av_cold int ff_mjpeg_decode_init(AVCodecContext *avctx)
 /* quantize tables */
 int ff_mjpeg_decode_dqt(MJpegDecodeContext *s)
 {
-    int len, index, i, j;
+    int len, index, i;
 
     len = get_bits(&s->gb, 16) - 2;
 
@@ -187,13 +187,12 @@ int ff_mjpeg_decode_dqt(MJpegDecodeContext *s)
         av_log(s->avctx, AV_LOG_DEBUG, "index=%d\n", index);
         /* read quant table */
         for (i = 0; i < 64; i++) {
-            j = s->scantable.permutated[i];
-            s->quant_matrixes[index][j] = get_bits(&s->gb, pr ? 16 : 8);
+            s->quant_matrixes[index][i] = get_bits(&s->gb, pr ? 16 : 8);
         }
 
         // XXX FIXME finetune, and perhaps add dc too
-        s->qscale[index] = FFMAX(s->quant_matrixes[index][s->scantable.permutated[1]],
-                                 s->quant_matrixes[index][s->scantable.permutated[8]]) >> 1;
+        s->qscale[index] = FFMAX(s->quant_matrixes[index][1],
+                                 s->quant_matrixes[index][8]) >> 1;
         av_log(s->avctx, AV_LOG_DEBUG, "qscale[%d]: %d\n",
                index, s->qscale[index]);
         len -= 1 + 64 * (1+pr);
@@ -723,7 +722,7 @@ static int decode_block(MJpegDecodeContext *s, int16_t *block, int component,
                 return AVERROR_INVALIDDATA;
             }
             j        = s->scantable.permutated[i];
-            block[j] = level * quant_matrix[j];
+            block[j] = level * quant_matrix[i];
         }
     } while (i < 63);
     CLOSE_READER(re, &s->gb);}
@@ -785,14 +784,14 @@ static int decode_block_progressive(MJpegDecodeContext *s, int16_t *block,
                 if (i >= se) {
                     if (i == se) {
                         j = s->scantable.permutated[se];
-                        block[j] = level * (quant_matrix[j] << Al);
+                        block[j] = level * (quant_matrix[se] << Al);
                         break;
                     }
                     av_log(s->avctx, AV_LOG_ERROR, "error count: %d\n", i);
                     return AVERROR_INVALIDDATA;
                 }
                 j = s->scantable.permutated[i];
-                block[j] = level * (quant_matrix[j] << Al);
+                block[j] = level * (quant_matrix[i] << Al);
             } else {
                 if (run == 0xF) {// ZRL - skip 15 coefficients
                     i += 15;
@@ -825,7 +824,7 @@ static int decode_block_progressive(MJpegDecodeContext *s, int16_t *block,
     UPDATE_CACHE(re, &s->gb);                                       \
     sign = block[j] >> 15;                                          \
     block[j] += SHOW_UBITS(re, &s->gb, 1) *                         \
-                ((quant_matrix[j] ^ sign) - sign) << Al;            \
+                ((quant_matrix[i] ^ sign) - sign) << Al;            \
     LAST_SKIP_BITS(re, &s->gb, 1);                                  \
 }
 
@@ -871,7 +870,7 @@ static int decode_block_refinement(MJpegDecodeContext *s, int16_t *block,
                 ZERO_RUN;
                 j = s->scantable.permutated[i];
                 val--;
-                block[j] = ((quant_matrix[j] << Al) ^ val) - val;
+                block[j] = ((quant_matrix[i] << Al) ^ val) - val;
                 if (i == se) {
                     if (i > *last_nnz)
                         *last_nnz = i;