jpeg2000: Split codeblock decoding from the main tile decoding

That loop is completely stand-alone.

libavcodec/jpeg2000dec.c

@@ -1060,14 +1060,12 @@ static inline void mct_decode(Jpeg2000DecoderContext *s, Jpeg2000Tile *tile)
     s->dsp.mct_decode[tile->codsty[0].transform](src[0], src[1], src[2], csize);
 }
 
-static int jpeg2000_decode_tile(Jpeg2000DecoderContext *s, Jpeg2000Tile *tile,
-                                AVFrame *picture)
+static void tile_codeblocks(Jpeg2000DecoderContext *s, Jpeg2000Tile *tile)
 {
+    Jpeg2000T1Context t1;
+
     int compno, reslevelno, bandno;
-    int x, y;
 
-    uint8_t *line;
-    Jpeg2000T1Context t1;
     /* Loop on tile components */
 
     for (compno = 0; compno < s->ncomponents; compno++) {
@@ -1116,6 +1114,17 @@ static int jpeg2000_decode_tile(Jpeg2000DecoderContext *s, Jpeg2000Tile *tile,
         /* inverse DWT */
         ff_dwt_decode(&comp->dwt, codsty->transform == FF_DWT97 ? (void*)comp->f_data : (void*)comp->i_data);
     } /*end comp */
+}
+
+static int jpeg2000_decode_tile(Jpeg2000DecoderContext *s, Jpeg2000Tile *tile,
+                                AVFrame *picture)
+{
+    int compno;
+    int x, y;
+
+    uint8_t *line;
+
+    tile_codeblocks(s, tile);
 
     /* inverse MCT transformation */
     if (tile->codsty[0].mct)