avcodec/mpegvideo_motion: Check P field references

If a reference is unavailable use a field from the current
picture
Fixes null pointer dereference

Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
This commit is contained in:
Michael Niedermayer 2013-04-18 19:53:00 +02:00
parent 4c8ce750ab
commit 23daee0dcc

View File

@ -809,7 +809,8 @@ static av_always_inline void MPV_motion_internal(MpegEncContext *s,
s->mv[dir][1][0], s->mv[dir][1][1], 8, mb_y);
}
} else {
if(s->picture_structure != s->field_select[dir][0] + 1 && s->pict_type != AV_PICTURE_TYPE_B && !s->first_field){
if( s->picture_structure != s->field_select[dir][0] + 1 && s->pict_type != AV_PICTURE_TYPE_B && !s->first_field
|| !ref_picture[0]){
ref_picture = s->current_picture_ptr->f.data;
}