make zero motion vector threshold user setable

Originally committed as revision 5348 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/avcodec.h

@@ -1967,6 +1967,14 @@ typedef struct AVCodecContext {
      * - decoding: unused
      */
     int scenechange_factor;
+
+    /**
+     *
+     * note: value depends upon the compare functin used for fullpel ME
+     * - encoding: set by user.
+     * - decoding: unused
+     */
+    int mv0_threshold;
 } AVCodecContext;
 
 /**

libavcodec/motion_est_template.c

@@ -896,7 +896,8 @@ static always_inline int epzs_motion_search_internal(MpegEncContext * s, int *mx
         CHECK_CLIPED_MV((last_mv[ref_mv_xy][0]*ref_mv_scale + (1<<15))>>16,
                         (last_mv[ref_mv_xy][1]*ref_mv_scale + (1<<15))>>16)
     }else{
-        if(dmin<h*h && ( P_LEFT[0]    |P_LEFT[1]
+        if(dmin<((h*h*s->avctx->mv0_threshold)>>8)
+                    && ( P_LEFT[0]    |P_LEFT[1]
                         |P_TOP[0]     |P_TOP[1]
                         |P_TOPRIGHT[0]|P_TOPRIGHT[1])==0){
             *mx_ptr= 0;

libavcodec/utils.c

@@ -739,6 +739,7 @@ static AVOption options[]={
 {"partp8x8", NULL, 0, FF_OPT_TYPE_CONST, X264_PART_P8X8, INT_MIN, INT_MAX, V|E, "partitions"},
 {"partb8x8", NULL, 0, FF_OPT_TYPE_CONST, X264_PART_B8X8, INT_MIN, INT_MAX, V|E, "partitions"},
 {"sc_factor", NULL, OFFSET(scenechange_factor), FF_OPT_TYPE_INT, 6, 0, INT_MAX, V|E},
+{"mv0_threshold", NULL, OFFSET(mv0_threshold), FF_OPT_TYPE_INT, 256, 0, INT_MAX, V|E},
 {NULL},
 };
 
@@ -793,6 +794,7 @@ void avcodec_get_context_defaults(AVCodecContext *s){
     s->frame_skip_cmp= FF_CMP_DCTMAX;
     s->nsse_weight= 8;
     s->sample_fmt= SAMPLE_FMT_S16; // FIXME: set to NONE
+    s->mv0_threshold= 256;
 
     s->intra_quant_bias= FF_DEFAULT_QUANT_BIAS;
     s->inter_quant_bias= FF_DEFAULT_QUANT_BIAS;