fixed interlaced encoding

git-svn-id: file:///var/local/repositories/ffmpeg/trunk@2590 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

libavcodec/mpegvideo.c

@@ -404,7 +404,8 @@ int MPV_common_init(MpegEncContext *s)
     s->y_dc_scale_table=
     s->c_dc_scale_table= ff_mpeg1_dc_scale_table;
     s->chroma_qscale_table= ff_default_chroma_qscale_table;
-    s->progressive_sequence= 
+    if (!s->encoding)
+        s->progressive_sequence= 1;
     s->progressive_frame= 1;
 
     y_size = (2 * s->mb_width + 2) * (2 * s->mb_height + 2);