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h264: add 3 pixels below for subpixel filter wait position

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If the motion vector is at a subpixel position, we need 3 pixels below
the motion vector's wholepel position available, not 2, since the MC
filter is a sixtap filter for the hpel position, and then a bilin filter
for the qpel position.

This patch fixes highly irreproducible (0.1%) fate failures in frame 2
and 4 of h264-conformance-cama2_vtc_b (e.g. first P-frame, first field,
last line of MB x=40,y=2 and second field and last lines of MBs x=39-40,
y=3). These used pre-loopfilter instead of post-loopfilter data because
the await_progress() waited for one line too little in that field, and
the motion vector of these particular MBs happened to align exactly to a
position where that demonstrates the bug.

CC: libav-stable@libav.org

Signed-off-by: Luca Barbato <lu_zero@gentoo.org>
This commit is contained in:
Ronald S. Bultje 2013-01-15 08:38:54 -08:00 committed by Luca Barbato
parent f924d52975
commit fb845ffdd3
1 changed files with 4 additions and 3 deletions
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7
libavcodec/h264.c
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@ -290,10 +290,11 @@ static inline int get_lowest_part_list_y(H264Context *h, Picture *pic, int n,
int height, int y_offset, int list)
{
int raw_my = h->mv_cache[list][scan8[n]][1];
int filter_height = (raw_my & 3) ? 2 : 0;
int filter_height_up = (raw_my & 3) ? 2 : 0;
int filter_height_down = (raw_my & 3) ? 3 : 0;
int full_my = (raw_my >> 2) + y_offset;
int top = full_my - filter_height;
int bottom = full_my + filter_height + height;
int top = full_my - filter_height_up;
int bottom = full_my + filter_height_down + height;
return FFMAX(abs(top), bottom);
}