[SCM] libav/experimental: Fix dual prime motion compensation in field pictures. Fixes issue1125.

[siretart at users.alioth.debian.org]

The following commit has been merged in the experimental branch:
commit f0ec23943861c42b2633c821ddfac45c61899973
Author: Michael Niedermayer <michaelni at gmx.at>
Date:   Mon Nov 30 02:37:03 2009 +0000

    Fix dual prime motion compensation in field pictures.
    Fixes issue1125.
    
    Originally committed as revision 20666 to svn://svn.ffmpeg.org/ffmpeg/trunk

diff --git a/libavcodec/mpeg12.c b/libavcodec/mpeg12.c
index 74b8eea..2f8928d 100644
--- a/libavcodec/mpeg12.c
+++ b/libavcodec/mpeg12.c
@@ -448,18 +448,20 @@ static int mpeg_decode_mb(MpegEncContext *s,
                 for(i=0;i<2;i++) {
                     if (USES_LIST(mb_type, i)) {
                         int dmx, dmy, mx, my, m;
+                        const int my_shift= s->picture_structure == PICT_FRAME;
+
                         mx = mpeg_decode_motion(s, s->mpeg_f_code[i][0],
                                                 s->last_mv[i][0][0]);
                         s->last_mv[i][0][0] = mx;
                         s->last_mv[i][1][0] = mx;
                         dmx = get_dmv(s);
                         my = mpeg_decode_motion(s, s->mpeg_f_code[i][1],
-                                                s->last_mv[i][0][1] >> 1);
+                                                s->last_mv[i][0][1] >> my_shift);
                         dmy = get_dmv(s);
 
 
-                        s->last_mv[i][0][1] = my<<1;
-                        s->last_mv[i][1][1] = my<<1;
+                        s->last_mv[i][0][1] = my<<my_shift;
+                        s->last_mv[i][1][1] = my<<my_shift;
 
                         s->mv[i][0][0] = mx;
                         s->mv[i][0][1] = my;

-- 
Libav/FFmpeg packaging