h264: move the DPB init/uninit to init_context()/free_context()

Currently, the DPB is initialized in alloc_tables() and uninitialized in
free_tables(), but those functions manage frame size-dependent
variables, so DPB management does not logically belong in there.

Since we want the init/uninit to happen exactly once per the context
lifetime, init_context()/free_context() are the proper place for this
code.

libavcodec/h264.c

@@ -355,14 +355,6 @@ void ff_h264_free_tables(H264Context *h, int free_rbsp)
     av_buffer_pool_uninit(&h->motion_val_pool);
     av_buffer_pool_uninit(&h->ref_index_pool);
 
-    if (free_rbsp && h->DPB) {
-        for (i = 0; i < H264_MAX_PICTURE_COUNT; i++)
-            ff_h264_unref_picture(h, &h->DPB[i]);
-        av_freep(&h->DPB);
-    }
-
-    h->cur_pic_ptr = NULL;
-
     for (i = 0; i < h->nb_slice_ctx; i++) {
         H264SliceContext *sl = &h->slice_ctx[i];
 
@@ -392,7 +384,7 @@ int ff_h264_alloc_tables(H264Context *h)
 {
     const int big_mb_num = h->mb_stride * (h->mb_height + 1);
     const int row_mb_num = h->mb_stride * 2 * h->avctx->thread_count;
-    int x, y, i;
+    int x, y;
 
     FF_ALLOCZ_OR_GOTO(h->avctx, h->intra4x4_pred_mode,
                       row_mb_num * 8 * sizeof(uint8_t), fail)
@@ -438,15 +430,6 @@ int ff_h264_alloc_tables(H264Context *h)
     if (!h->dequant4_coeff[0])
         h264_init_dequant_tables(h);
 
-    if (!h->DPB) {
-        h->DPB = av_mallocz_array(H264_MAX_PICTURE_COUNT, sizeof(*h->DPB));
-        if (!h->DPB)
-            goto fail;
-        for (i = 0; i < H264_MAX_PICTURE_COUNT; i++)
-            av_frame_unref(&h->DPB[i].f);
-        av_frame_unref(&h->cur_pic.f);
-    }
-
     return 0;
 
 fail:
@@ -613,6 +596,13 @@ static int h264_init_context(AVCodecContext *avctx, H264Context *h)
         return AVERROR(ENOMEM);
     }
 
+    h->DPB = av_mallocz_array(H264_MAX_PICTURE_COUNT, sizeof(*h->DPB));
+    if (!h->DPB)
+        return AVERROR(ENOMEM);
+    for (i = 0; i < H264_MAX_PICTURE_COUNT; i++)
+        av_frame_unref(&h->DPB[i].f);
+    av_frame_unref(&h->cur_pic.f);
+
     for (i = 0; i < h->nb_slice_ctx; i++)
         h->slice_ctx[i].h264 = h;
 
@@ -1756,6 +1746,14 @@ av_cold void ff_h264_free_context(H264Context *h)
 
     ff_h264_free_tables(h, 1); // FIXME cleanup init stuff perhaps
 
+    if (h->DPB) {
+        for (i = 0; i < H264_MAX_PICTURE_COUNT; i++)
+            ff_h264_unref_picture(h, &h->DPB[i]);
+        av_freep(&h->DPB);
+    }
+
+    h->cur_pic_ptr = NULL;
+
     av_freep(&h->slice_ctx);
     h->nb_slice_ctx = 0;
 

libavcodec/h264_slice.c

@@ -454,6 +454,7 @@ int ff_h264_update_thread_context(AVCodecContext *dst,
 
     if (!inited) {
         H264SliceContext *orig_slice_ctx = h->slice_ctx;
+        H264Picture *orig_DPB = h->DPB;
 
         for (i = 0; i < MAX_SPS_COUNT; i++)
             av_freep(h->sps_buffers + i);
@@ -471,6 +472,7 @@ int ff_h264_update_thread_context(AVCodecContext *dst,
         h->cur_pic.tf.f = &h->cur_pic.f;
 
         h->slice_ctx = orig_slice_ctx;
+        h->DPB       = orig_DPB;
 
         memset(&h->slice_ctx[0].er,         0, sizeof(h->slice_ctx[0].er));
         memset(&h->slice_ctx[0].mb,         0, sizeof(h->slice_ctx[0].mb));
@@ -478,7 +480,6 @@ int ff_h264_update_thread_context(AVCodecContext *dst,
         memset(&h->slice_ctx[0].mb_padding, 0, sizeof(h->slice_ctx[0].mb_padding));
 
         h->avctx             = dst;
-        h->DPB               = NULL;
         h->qscale_table_pool = NULL;
         h->mb_type_pool      = NULL;
         h->ref_index_pool    = NULL;