support skiping of mb rows during decoding

Originally committed as revision 3253 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/avcodec.h

@@ -17,7 +17,7 @@ extern "C" {
 
 #define FFMPEG_VERSION_INT     0x000408
 #define FFMPEG_VERSION         "0.4.8"
-#define LIBAVCODEC_BUILD       4716
+#define LIBAVCODEC_BUILD       4717
 
 #define LIBAVCODEC_VERSION_INT FFMPEG_VERSION_INT
 #define LIBAVCODEC_VERSION     FFMPEG_VERSION
@@ -1605,6 +1605,20 @@ typedef struct AVCodecContext {
      * - decoding: unused
      */
      int nsse_weight;
+
+    /**
+     * number of macroblock rows at the top which are skiped.
+     * - encoding: unused
+     * - decoding: set by user
+     */
+     int skip_top;
+
+    /**
+     * number of macroblock rows at the bottom which are skiped.
+     * - encoding: unused
+     * - decoding: set by user
+     */
+     int skip_bottom;
 } AVCodecContext;