Make timestamp interpolation work with mpeg2 field pictures.

Cleaner/simpler solutions are welcome.

Originally committed as revision 12156 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/avcodec.h

@@ -2788,6 +2788,7 @@ typedef struct AVCodecParserContext {
     /* video info */
     int pict_type; /* XXX: Put it back in AVCodecContext. */
     int repeat_pict; /* XXX: Put it back in AVCodecContext. */
+    int parity;
     int64_t pts;     /* pts of the current frame */
     int64_t dts;     /* dts of the current frame */
 

libavcodec/mpegvideo_parser.c

@@ -36,6 +36,7 @@ static void mpegvideo_extract_headers(AVCodecParserContext *s,
     int horiz_size_ext, vert_size_ext, bit_rate_ext;
 //FIXME replace the crap with get_bits()
     s->repeat_pict = 0;
+    s->parity = 0;
     buf_end = buf + buf_size;
     while (buf < buf_end) {
         start_code= -1;
@@ -105,8 +106,11 @@ static void mpegvideo_extract_headers(AVCodecParserContext *s,
 
                         /* the packet only represents half a frame
                            XXX,FIXME maybe find a different solution */
-                        if(picture_structure != 3)
+                        if(picture_structure != 3){
                             s->repeat_pict = -1;
+                            s->parity = picture_structure-1;
+                        }else
+                            s->parity = !top_field_first;
                     }
                     break;
                 }