fix mjpeg.mov

Originally committed as revision 8738 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/mjpeg.c

@@ -1760,7 +1760,7 @@ static int mjpeg_decode_dri(MJpegDecodeContext *s)
 
 static int mjpeg_decode_app(MJpegDecodeContext *s)
 {
-    int len, id;
+    int len, id, i;
 
     len = get_bits(&s->gb, 16);
     if (len < 5)
@@ -1791,7 +1791,9 @@ static int mjpeg_decode_app(MJpegDecodeContext *s)
             s->buggy_avid = 1;
 //        if (s->first_picture)
 //            printf("mjpeg: workarounding buggy AVID\n");
-        s->bottom_field = get_bits(&s->gb, 8) == 2;
+        i = get_bits(&s->gb, 8);
+        if     (i==2) s->bottom_field= 1;
+        else if(i==1) s->bottom_field= 0;
 #if 0
         skip_bits(&s->gb, 8);
         skip_bits(&s->gb, 32);