[x264-devel] [PATCH] fix bug of weighted bipred according to Rec. ITU-T H.264 (10/2016) 8.4.3

[Lingjiang Fang]

From: Lingjiang Fang <vacingfang at tencent.com>

---
 common/macroblock.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/common/macroblock.c b/common/macroblock.c
index 9a3c7132..638a5c42 100644
--- a/common/macroblock.c
+++ b/common/macroblock.c
@@ -1890,13 +1890,17 @@ void x264_macroblock_bipred_init( x264_t *h )
                 int poc0 = l0->i_poc + mbfield*l0->i_delta_poc[field^(i_ref0&1)];
                 for( int i_ref1 = 0; i_ref1 < (h->i_ref[1]<<mbfield); i_ref1++ )
                 {
+                    int use_default = 0;
                     int dist_scale_factor;
                     x264_frame_t *l1 = h->fref[1][i_ref1>>mbfield];
                     int cur_poc = h->fdec->i_poc + mbfield*h->fdec->i_delta_poc[field];
                     int poc1 = l1->i_poc + mbfield*l1->i_delta_poc[field^(i_ref1&1)];
                     int td = x264_clip3( poc1 - poc0, -128, 127 );
                     if( td == 0 /* || pic0 is a long-term ref */ )
+                    {
                         dist_scale_factor = 256;
+                        use_default = 1;
+                    }
                     else
                     {
                         int tb = x264_clip3( cur_poc - poc0, -128, 127 );
@@ -1907,7 +1911,7 @@ void x264_macroblock_bipred_init( x264_t *h )
                     h->mb.dist_scale_factor_buf[mbfield][field][i_ref0][i_ref1] = dist_scale_factor;

                     dist_scale_factor >>= 2;
-                    if( h->param.analyse.b_weighted_bipred
+                    if( !use_default && h->param.analyse.b_weighted_bipred
                           && dist_scale_factor >= -64
                           && dist_scale_factor <= 128 )
                     {
--
2.29.2