h264: avoid pointless copying of ref lists

ref_list is constructed from other fields per slice when needed, so do
not copy it for both frame and slice threading.
default_ref_list is constructed per frame and still needs to be copied
to per-slice contexts for slice threading, but a copy is not needed for
frame threading.

libavcodec/h264.c

@@ -1253,7 +1253,7 @@ static int decode_update_thread_context(AVCodecContext *dst,
 
     // reference lists
     copy_fields(h, h1, ref_count, list_count);
-    copy_fields(h, h1, ref_list, intra_gb);
+    copy_fields(h, h1, ref2frm, intra_gb);
     copy_fields(h, h1, short_ref, cabac_init_idc);
 
     copy_picture_range(h->short_ref, h1->short_ref, 32, s, s1);
@@ -2369,7 +2369,6 @@ static int clone_slice(H264Context *dst, H264Context *src)
     memcpy(dst->short_ref,        src->short_ref,        sizeof(dst->short_ref));
     memcpy(dst->long_ref,         src->long_ref,         sizeof(dst->long_ref));
     memcpy(dst->default_ref_list, src->default_ref_list, sizeof(dst->default_ref_list));
-    memcpy(dst->ref_list,         src->ref_list,         sizeof(dst->ref_list));
 
     memcpy(dst->dequant4_coeff,   src->dequant4_coeff,   sizeof(src->dequant4_coeff));
     memcpy(dst->dequant8_coeff,   src->dequant8_coeff,   sizeof(src->dequant8_coeff));

libavcodec/h264.h

@@ -481,9 +481,9 @@ typedef struct H264Context {
 
     int redundant_pic_count;
 
+    Picture default_ref_list[2][32]; ///< base reference list for all slices of a coded picture
     Picture *short_ref[32];
     Picture *long_ref[32];
-    Picture default_ref_list[2][32]; ///< base reference list for all slices of a coded picture
     Picture *delayed_pic[MAX_DELAYED_PIC_COUNT + 2]; // FIXME size?
     int last_pocs[MAX_DELAYED_PIC_COUNT];
     Picture *next_output_pic;