h264: decode the MMCOs into per-slice contexts

They are stored in the slice header, so technically they are per-slice
(though they must be the same in every slice). This will simplify the
following commits.

libavcodec/h264.h

@@ -439,6 +439,9 @@ typedef struct H264SliceContext {
     CABACContext cabac;
     uint8_t cabac_state[1024];
     int cabac_init_idc;
+
+    MMCO mmco[MAX_MMCO_COUNT];
+    int  nb_mmco;
 } H264SliceContext;
 
 /**
@@ -671,10 +674,10 @@ void ff_h264_remove_all_refs(H264Context *h);
  */
 int ff_h264_execute_ref_pic_marking(H264Context *h, MMCO *mmco, int mmco_count);
 
-int ff_h264_decode_ref_pic_marking(H264Context *h, GetBitContext *gb,
-                                   int first_slice);
+int ff_h264_decode_ref_pic_marking(const H264Context *h, H264SliceContext *sl,
+                                   GetBitContext *gb);
 
-int ff_generate_sliding_window_mmcos(H264Context *h, int first_slice);
+int ff_generate_sliding_window_mmcos(const H264Context *h, H264SliceContext *sl);
 
 void ff_h264_hl_decode_mb(const H264Context *h, H264SliceContext *sl);
 int ff_h264_decode_init(AVCodecContext *avctx);

libavcodec/h264_refs.c

@@ -536,9 +536,10 @@ static int check_opcodes(MMCO *mmco1, MMCO *mmco2, int n_mmcos)
     return 0;
 }
 
-int ff_generate_sliding_window_mmcos(H264Context *h, int first_slice)
+int ff_generate_sliding_window_mmcos(const H264Context *h,
+                                     H264SliceContext *sl)
 {
-    MMCO mmco_temp[MAX_MMCO_COUNT], *mmco = first_slice ? h->mmco : mmco_temp;
+    MMCO *mmco = sl->mmco;
     int nb_mmco = 0, i = 0;
 
     assert(h->long_ref_count + h->short_ref_count <= h->ps.sps->ref_frame_count);
@@ -557,16 +558,8 @@ int ff_generate_sliding_window_mmcos(H264Context *h, int first_slice)
         }
     }
 
-    if (first_slice) {
-        h->nb_mmco = nb_mmco;
-    } else if (!first_slice && nb_mmco >= 0 &&
-               (nb_mmco != h->nb_mmco ||
-                (i = check_opcodes(h->mmco, mmco_temp, nb_mmco)))) {
-        av_log(h->avctx, AV_LOG_ERROR,
-               "Inconsistent MMCO state between slices [%d, %d, %d]\n",
-               nb_mmco, h->nb_mmco, i);
-        return AVERROR_INVALIDDATA;
-    }
+    sl->nb_mmco = nb_mmco;
+
     return 0;
 }
 
@@ -743,11 +736,11 @@ int ff_h264_execute_ref_pic_marking(H264Context *h, MMCO *mmco, int mmco_count)
     return (h->avctx->err_recognition & AV_EF_EXPLODE) ? err : 0;
 }
 
-int ff_h264_decode_ref_pic_marking(H264Context *h, GetBitContext *gb,
-                                   int first_slice)
+int ff_h264_decode_ref_pic_marking(const H264Context *h, H264SliceContext *sl,
+                                   GetBitContext *gb)
 {
     int i, ret;
-    MMCO mmco_temp[MAX_MMCO_COUNT], *mmco = first_slice ? h->mmco : mmco_temp;
+    MMCO *mmco = sl->mmco;
     int nb_mmco = 0;
 
     if (h->nal_unit_type == NAL_IDR_SLICE) { // FIXME fields
@@ -803,25 +796,15 @@ int ff_h264_decode_ref_pic_marking(H264Context *h, GetBitContext *gb,
             }
             nb_mmco = i;
         } else {
-            if (first_slice) {
-                ret = ff_generate_sliding_window_mmcos(h, first_slice);
-                if (ret < 0 && h->avctx->err_recognition & AV_EF_EXPLODE)
-                    return ret;
-            }
+            ret = ff_generate_sliding_window_mmcos(h, sl);
+            if (ret < 0 && h->avctx->err_recognition & AV_EF_EXPLODE)
+                return ret;
             nb_mmco = -1;
         }
     }
 
-    if (first_slice && nb_mmco != -1) {
-        h->nb_mmco = nb_mmco;
-    } else if (!first_slice && nb_mmco >= 0 &&
-               (nb_mmco != h->nb_mmco ||
-                check_opcodes(h->mmco, mmco_temp, nb_mmco))) {
-        av_log(h->avctx, AV_LOG_ERROR,
-               "Inconsistent MMCO state between slices [%d, %d]\n",
-               nb_mmco, h->nb_mmco);
-        return AVERROR_INVALIDDATA;
-    }
+    if (nb_mmco != -1)
+        sl->nb_mmco = nb_mmco;
 
     return 0;
 }

libavcodec/h264_slice.c

@@ -1201,10 +1201,12 @@ static int h264_slice_header_parse(H264Context *h, H264SliceContext *sl)
             h->cur_pic_ptr->frame_num = h->poc.prev_frame_num;
             ff_thread_report_progress(&h->cur_pic_ptr->tf, INT_MAX, 0);
             ff_thread_report_progress(&h->cur_pic_ptr->tf, INT_MAX, 1);
-            ret = ff_generate_sliding_window_mmcos(h, 1);
+
+            ret = ff_generate_sliding_window_mmcos(h, sl);
             if (ret < 0 && (h->avctx->err_recognition & AV_EF_EXPLODE))
                 return ret;
-            ret = ff_h264_execute_ref_pic_marking(h, h->mmco, h->nb_mmco);
+
+            ret = ff_h264_execute_ref_pic_marking(h, sl->mmco, sl->nb_mmco);
             if (ret < 0 && (h->avctx->err_recognition & AV_EF_EXPLODE))
                 return ret;
             /* Error concealment: If a ref is missing, copy the previous ref
@@ -1342,15 +1344,8 @@ static int h264_slice_header_parse(H264Context *h, H264SliceContext *sl)
         ff_h264_pred_weight_table(&sl->gb, sps, sl->ref_count,
                                   sl->slice_type_nos, &sl->pwt);
 
-    // If frame-mt is enabled, only update mmco tables for the first slice
-    // in a field. Subsequent slices can temporarily clobber h->nb_mmco
-    // or h->mmco, which will cause ref list mix-ups and decoding errors
-    // further down the line. This may break decoding if the first slice is
-    // corrupt, thus we only do this if frame-mt is enabled.
     if (h->nal_ref_idc) {
-        ret = ff_h264_decode_ref_pic_marking(h, &sl->gb,
-                                             !(h->avctx->active_thread_type & FF_THREAD_FRAME) ||
-                                             h->current_slice == 0);
+        ret = ff_h264_decode_ref_pic_marking(h, sl, &sl->gb);
         if (ret < 0 && (h->avctx->err_recognition & AV_EF_EXPLODE))
             return AVERROR_INVALIDDATA;
     }
@@ -1441,10 +1436,14 @@ int ff_h264_decode_slice_header(H264Context *h, H264SliceContext *sl)
         sl->resync_mb_y = sl->mb_y = sl->mb_y + 1;
     assert(sl->mb_y < h->mb_height);
 
-    if (!h->setup_finished)
+    if (!h->setup_finished) {
         ff_h264_init_poc(h->cur_pic_ptr->field_poc, &h->cur_pic_ptr->poc,
                          h->ps.sps, &h->poc, h->picture_structure, h->nal_ref_idc);
 
+        memcpy(h->mmco, sl->mmco, sl->nb_mmco * sizeof(*h->mmco));
+        h->nb_mmco = sl->nb_mmco;
+    }
+
     ret = ff_h264_build_ref_list(h, sl);
     if (ret < 0)
         return ret;