Enable direct_spatial_mv_pred_flag for B frame

this flag also improve the quality.

Fixes #28

Signed-off-by: Pengfei Qu <[email protected]>
(cherry picked from commit aa7809c)

Author: Pengfei Qu

encode/avcenc.c

@@ -642,7 +642,7 @@ static void avcenc_update_slice_parameter(int slice_type)
     slice_param->num_macroblocks = picture_height_in_mbs * picture_width_in_mbs; 
     slice_param->pic_parameter_set_id = 0;
     slice_param->slice_type = slice_type;
-    slice_param->direct_spatial_mv_pred_flag = 0;
+    slice_param->direct_spatial_mv_pred_flag = 1;
     slice_param->num_ref_idx_l0_active_minus1 = 0;      /* FIXME: ??? */
     slice_param->num_ref_idx_l1_active_minus1 = 0;
     slice_param->cabac_init_idc = 0;