mpegvideo_enc: factor expression out

Fixes "warning: dc[0..5] may be used uninitialized in this function"
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/mpegvideo_enc.c

@@ -2844,6 +2844,7 @@ static int encode_thread(AVCodecContext *c, void *arg){
                         int16_t ac[6][16];
                         const int mvdir= (best_s.mv_dir&MV_DIR_BACKWARD) ? 1 : 0;
                         static const int dquant_tab[4]={-1,1,-2,2};
+                        int storecoefs = s->mb_intra && s->dc_val[0];
 
                         av_assert2(backup_s.dquant == 0);
 
@@ -2863,7 +2864,7 @@ static int encode_thread(AVCodecContext *c, void *arg){
                             if(qp < s->avctx->qmin || qp > s->avctx->qmax)
                                 continue;
                             backup_s.dquant= dquant;
-                            if(s->mb_intra && s->dc_val[0]){
+                            if(storecoefs){
                                 for(i=0; i<6; i++){
                                     dc[i]= s->dc_val[0][ s->block_index[i] ];
                                     memcpy(ac[i], s->ac_val[0][s->block_index[i]], sizeof(int16_t)*16);
@@ -2873,7 +2874,7 @@ static int encode_thread(AVCodecContext *c, void *arg){
                             encode_mb_hq(s, &backup_s, &best_s, CANDIDATE_MB_TYPE_INTER /* wrong but unused */, pb, pb2, tex_pb,
                                          &dmin, &next_block, s->mv[mvdir][0][0], s->mv[mvdir][0][1]);
                             if(best_s.qscale != qp){
-                                if(s->mb_intra && s->dc_val[0]){
+                                if(storecoefs){
                                     for(i=0; i<6; i++){
                                         s->dc_val[0][ s->block_index[i] ]= dc[i];
                                         memcpy(s->ac_val[0][s->block_index[i]], ac[i], sizeof(int16_t)*16);