h264: eliminate default_ref_list

According to the spec, the reference list for a slice should be
constructed by first generating an initial (what we now call "default")
reference list and then optionally applying modifications to it.

Our code has an optimization where the initial reference list is
constructed for the first inter slice and then rebuilt for other slices
if needed. This, however, adds complexity to the code, requires an extra
2.5kB array in the codec context and there is no reason to think that it
has any positive effect on performance. Therefore, simplify the code by
generating the reference list from scratch for each slice.

1 files changed, 21 insertions, 25 deletions

diff --git a/libavcodec/h264_refs.c b/libavcodec/h264_refs.c
index adc2213944..46b51e0bfd 100644
--- a/libavcodec/h264_refs.c
+++ b/libavcodec/h264_refs.c
@@ -119,7 +119,7 @@ static int add_sorted(H264Picture **sorted, H264Picture **src, int len, int limi
     return out_i;
 }
 
-int ff_h264_fill_default_ref_list(H264Context *h, H264SliceContext *sl)
+static void h264_initialise_ref_list(H264Context *h, H264SliceContext *sl)
 {
     int i, len;
 
@@ -138,52 +138,51 @@ int ff_h264_fill_default_ref_list(H264Context *h, H264SliceContext *sl)
             len += add_sorted(sorted + len, h->short_ref, h->short_ref_count, cur_poc, 0 ^ list);
             assert(len <= 32);
 
-            len  = build_def_list(h->default_ref_list[list], FF_ARRAY_ELEMS(h->default_ref_list[0]),
+            len  = build_def_list(sl->ref_list[list], FF_ARRAY_ELEMS(sl->ref_list[0]),
                                   sorted, len, 0, h->picture_structure);
-            len += build_def_list(h->default_ref_list[list] + len,
-                                  FF_ARRAY_ELEMS(h->default_ref_list[0]) - len,
+            len += build_def_list(sl->ref_list[list] + len,
+                                  FF_ARRAY_ELEMS(sl->ref_list[0]) - len,
                                   h->long_ref, 16, 1, h->picture_structure);
 
             if (len < sl->ref_count[list])
-                memset(&h->default_ref_list[list][len], 0, sizeof(H264Ref) * (sl->ref_count[list] - len));
+                memset(&sl->ref_list[list][len], 0, sizeof(H264Ref) * (sl->ref_count[list] - len));
             lens[list] = len;
         }
 
         if (lens[0] == lens[1] && lens[1] > 1) {
             for (i = 0; i < lens[0] &&
-                        h->default_ref_list[0][i].parent->f->buf[0]->buffer ==
-                        h->default_ref_list[1][i].parent->f->buf[0]->buffer; i++);
+                        sl->ref_list[0][i].parent->f->buf[0]->buffer ==
+                        sl->ref_list[1][i].parent->f->buf[0]->buffer; i++);
             if (i == lens[0]) {
-                FFSWAP(H264Ref, h->default_ref_list[1][0], h->default_ref_list[1][1]);
+                FFSWAP(H264Ref, sl->ref_list[1][0], sl->ref_list[1][1]);
             }
         }
     } else {
-        len  = build_def_list(h->default_ref_list[0], FF_ARRAY_ELEMS(h->default_ref_list[0]),
+        len  = build_def_list(sl->ref_list[0], FF_ARRAY_ELEMS(sl->ref_list[0]),
                               h->short_ref, h->short_ref_count, 0, h->picture_structure);
-        len += build_def_list(h->default_ref_list[0] + len,
-                              FF_ARRAY_ELEMS(h->default_ref_list[0]) - len,
+        len += build_def_list(sl->ref_list[0] + len,
+                              FF_ARRAY_ELEMS(sl->ref_list[0]) - len,
                               h-> long_ref, 16, 1, h->picture_structure);
 
         if (len < sl->ref_count[0])
-            memset(&h->default_ref_list[0][len], 0, sizeof(H264Ref) * (sl->ref_count[0] - len));
+            memset(&sl->ref_list[0][len], 0, sizeof(H264Ref) * (sl->ref_count[0] - len));
     }
 #ifdef TRACE
     for (i = 0; i < sl->ref_count[0]; i++) {
         ff_tlog(h->avctx, "List0: %s fn:%d 0x%p\n",
-                (h->default_ref_list[0][i].long_ref ? "LT" : "ST"),
-                h->default_ref_list[0][i].pic_id,
-                h->default_ref_list[0][i].f->data[0]);
+                (sl->ref_list[0][i].long_ref ? "LT" : "ST"),
+                sl->ref_list[0][i].pic_id,
+                sl->ref_list[0][i].f->data[0]);
     }
     if (sl->slice_type_nos == AV_PICTURE_TYPE_B) {
         for (i = 0; i < sl->ref_count[1]; i++) {
             ff_tlog(h->avctx, "List1: %s fn:%d 0x%p\n",
-                    (h->default_ref_list[1][i].long_ref ? "LT" : "ST"),
-                    h->default_ref_list[1][i].pic_id,
-                    h->default_ref_list[1][i].f->data[0]);
+                    (sl->ref_list[1][i].long_ref ? "LT" : "ST"),
+                    sl->ref_list[1][i].pic_id,
+                    sl->ref_list[1][i].f->data[0]);
         }
     }
 #endif
-    return 0;
 }
 
 static void print_short_term(H264Context *h);
@@ -219,9 +218,9 @@ int ff_h264_decode_ref_pic_list_reordering(H264Context *h, H264SliceContext *sl)
     print_short_term(h);
     print_long_term(h);
 
-    for (list = 0; list < sl->list_count; list++) {
-        memcpy(sl->ref_list[list], h->default_ref_list[list], sl->ref_count[list] * sizeof(sl->ref_list[0][0]));
+    h264_initialise_ref_list(h, sl);
 
+    for (list = 0; list < sl->list_count; list++) {
         if (get_bits1(&sl->gb)) {    // ref_pic_list_modification_flag_l[01]
             int pred = h->curr_pic_num;
 
@@ -326,10 +325,7 @@ int ff_h264_decode_ref_pic_list_reordering(H264Context *h, H264SliceContext *sl)
         for (index = 0; index < sl->ref_count[list]; index++) {
             if (!sl->ref_list[list][index].parent) {
                 av_log(h->avctx, AV_LOG_ERROR, "Missing reference picture\n");
-                if (h->default_ref_list[list][0].parent)
-                    sl->ref_list[list][index] = h->default_ref_list[list][0];
-                else
-                    return -1;
+                return -1;
             }
         }
     }