Index: libavcodec/mjpeg.c
===================================================================
--- libavcodec/mjpeg.c	(revision 6260)
+++ libavcodec/mjpeg.c	(working copy)
@@ -1182,6 +1182,10 @@
         s->qscale_table= av_mallocz((s->width+15)/16);
 
         s->first_picture = 0;
+
+	s->avctx->vis_x0=s->avctx->vis_y1=0;
+	s->avctx->vis_x1=width;
+	s->avctx->vis_y1=height;
     }
 
     if(s->interlaced && s->bottom_field)
@@ -1465,21 +1469,29 @@
 static int mjpeg_decode_scan(MJpegDecodeContext *s){
     int i, mb_x, mb_y;
     const int nb_components=3;
+    int shft = 3 - s->avctx->lowres;
+    int x0 = s->avctx->vis_x0 >> shft, x1 = s->avctx->vis_x1+(1<<3-s->avctx->lowres)-1 >> shft;
+    int y0 = s->avctx->vis_y0 >> shft, y1 = s->avctx->vis_y1+(1<<3-s->avctx->lowres)-1 >> shft;
+    int px, py;
 
-    for(mb_y = 0; mb_y < s->mb_height; mb_y++) {
+    if (s->avctx->vis_x1<=s->avctx->vis_x0 || s->avctx->vis_y1<=s->avctx->vis_y0) return 0;
+    for(py = 0, mb_y = 0; mb_y < s->mb_height && py < y1; mb_y++, py += s->v_max) {
         for(mb_x = 0; mb_x < s->mb_width; mb_x++) {
             if (s->restart_interval && !s->restart_count)
                 s->restart_count = s->restart_interval;
 
             for(i=0;i<nb_components;i++) {
                 uint8_t *ptr;
-                int n, h, v, x, y, c, j;
+                int n, h, v, x, c, j;
                 n = s->nb_blocks[i];
                 c = s->comp_index[i];
                 h = s->h_scount[i];
                 v = s->v_scount[i];
                 x = 0;
-                y = 0;
+                ptr = s->picture.data[c] + ((s->linesize[c] * (v * mb_y) + h * mb_x) << 3 - s->avctx->lowres);
+		px = mb_x*s->h_max;
+                if (s->interlaced && s->bottom_field)
+                    ptr += s->linesize[c] >> 1;
                 for(j=0;j<n;j++) {
                     memset(s->block, 0, sizeof(s->block));
                     if (decode_block(s, s->block, i,
@@ -1488,19 +1500,18 @@
                         dprintf("error y=%d x=%d\n", mb_y, mb_x);
                         return -1;
                     }
-//                    dprintf("mb: %d %d processed\n", mb_y, mb_x);
-                    ptr = s->picture.data[c] +
-                        (((s->linesize[c] * (v * mb_y + y) * 8) +
-                        (h * mb_x + x) * 8) >> s->avctx->lowres);
-                    if (s->interlaced && s->bottom_field)
-                        ptr += s->linesize[c] >> 1;
-//av_log(NULL, AV_LOG_DEBUG, "%d %d %d %d %d %d %d %d \n", mb_x, mb_y, x, y, c, s->bottom_field, (v * mb_y + y) * 8, (h * mb_x + x) * 8);
-                    s->idct_put(ptr, s->linesize[c], s->block);
+                    if (px*h+s->v_max > x0*h && px < x1 && py*v+s->v_max > y0*v)
+			s->idct_put(ptr, s->linesize[c], s->block);
+                    ptr +=  1 << shft;
+		    px++;
                     if (++x == h) {
                         x = 0;
-                        y++;
+			px-=h;
+                        py++;
+                        ptr += s->linesize[c] - h << shft;
                     }
                 }
+		py-=v;
             }
             /* (< 1350) buggy workaround for Spectralfan.mov, should be fixed */
             if (s->restart_interval && (s->restart_interval < 1350) &&
Index: libavcodec/utils.c
===================================================================
--- libavcodec/utils.c	(revision 6260)
+++ libavcodec/utils.c	(working copy)
@@ -784,6 +784,9 @@
 
     s->palctrl = NULL;
     s->reget_buffer= avcodec_default_reget_buffer;
+
+    s->vis_x0=s->vis_y0=0;
+    s->vis_x1=s->vis_y1=INT_MAX;
 }
 
 /**
Index: libavcodec/avcodec.h
===================================================================
--- libavcodec/avcodec.h	(revision 6260)
+++ libavcodec/avcodec.h	(working copy)
@@ -1776,6 +1776,13 @@
      int lowres;
 
     /**
+     * Partial decoding. Visible rectangle: x0 <= x < x1
+     * - encoding: unused
+     * - decoding: set by user, defaults by avcodec_alloc_context, reset by codec if sizes was changed
+     */
+     int vis_x0, vis_x1, vis_y0, vis_y1;
+
+    /**
      * bitsream width / height. may be different from width/height if lowres
      * or other things are used
      * - encoding: unused