See http://www.nabble.com/-MacPorts---18551:-MPlayer-1.0rc2_3-fails-to-build-with-%2Bx264-td22110540.html

--- ./libavcodec/libx264.c.orig	2009-03-25 09:53:39.000000000 +0100
+++ ./libavcodec/libx264.c	2009-03-25 09:54:53.000000000 +0100
@@ -124,6 +124,8 @@
 {
     X264Context *x4 = avctx->priv_data;
 
+    av_freep(&avctx->extradata);
+
     if(x4->enc)
         x264_encoder_close(x4->enc);
 
@@ -162,7 +164,7 @@
 
     x4->params.i_bframe = avctx->max_b_frames;
     x4->params.b_cabac = avctx->coder_type == FF_CODER_TYPE_AC;
-    x4->params.b_bframe_adaptive = avctx->b_frame_strategy;
+    x4->params.i_bframe_adaptive = avctx->b_frame_strategy;
     x4->params.i_bframe_bias = avctx->bframebias;
     x4->params.b_bframe_pyramid = (avctx->flags2 & CODEC_FLAG2_BPYRAMID);
     avctx->has_b_frames= (avctx->flags2 & CODEC_FLAG2_BPYRAMID) ? 2 : !!avctx->max_b_frames;
@@ -225,8 +227,6 @@
     x4->params.analyse.i_me_range = avctx->me_range;
     x4->params.analyse.i_subpel_refine = avctx->me_subpel_quality;
 
-    x4->params.analyse.b_bidir_me = (avctx->bidir_refine > 0);
-    x4->params.analyse.b_bframe_rdo = (avctx->flags2 & CODEC_FLAG2_BRDO);
     x4->params.analyse.b_mixed_references =
         (avctx->flags2 & CODEC_FLAG2_MIXED_REFS);
     x4->params.analyse.b_chroma_me = (avctx->me_cmp & FF_CMP_CHROMA);