vaapi_encode_h265: Don't require uniform_spacing_flag

Though still use it if the tile arrangement matches.  Also try to keep the
fields in the same order as the standard.

libavcodec/vaapi_encode_h265.c

@@ -555,23 +555,42 @@ static int vaapi_encode_h265_init_sequence_params(AVCodecContext *avctx)
     pps->cu_qp_delta_enabled_flag = (ctx->va_rc_mode != VA_RC_CQP);
     pps->diff_cu_qp_delta_depth   = 0;
 
-    pps->pps_loop_filter_across_slices_enabled_flag = 1;
-
     if (ctx->tile_rows && ctx->tile_cols) {
-        pps->tiles_enabled_flag         = 1;
-        pps->uniform_spacing_flag       = 1;
-
-        pps->num_tile_rows_minus1       = ctx->tile_rows - 1;
-        pps->num_tile_columns_minus1    = ctx->tile_cols - 1;
-
-        pps->loop_filter_across_tiles_enabled_flag = 1;
+        int uniform_spacing;
+
+        pps->tiles_enabled_flag      = 1;
+        pps->num_tile_columns_minus1 = ctx->tile_cols - 1;
+        pps->num_tile_rows_minus1    = ctx->tile_rows - 1;
+
+        // Test whether the spacing provided matches the H.265 uniform
+        // spacing, and set the flag if it does.
+        uniform_spacing = 1;
+        for (i = 0; i <= pps->num_tile_columns_minus1 &&
+                    uniform_spacing; i++) {
+            if (ctx->col_width[i] !=
+                (i + 1) * ctx->slice_block_cols / ctx->tile_cols -
+                 i      * ctx->slice_block_cols / ctx->tile_cols)
+                uniform_spacing = 0;
+        }
+        for (i = 0; i <= pps->num_tile_rows_minus1 &&
+                    uniform_spacing; i++) {
+            if (ctx->row_height[i] !=
+                (i + 1) * ctx->slice_block_rows / ctx->tile_rows -
+                 i      * ctx->slice_block_rows / ctx->tile_rows)
+                uniform_spacing = 0;
+        }
+        pps->uniform_spacing_flag = uniform_spacing;
 
-        for (i = 0; i <= pps->num_tile_rows_minus1; i++)
-            pps->row_height_minus1[i]   = ctx->row_height[i] - 1;
         for (i = 0; i <= pps->num_tile_columns_minus1; i++)
             pps->column_width_minus1[i] = ctx->col_width[i] - 1;
+        for (i = 0; i <= pps->num_tile_rows_minus1; i++)
+            pps->row_height_minus1[i]   = ctx->row_height[i] - 1;
+
+        pps->loop_filter_across_tiles_enabled_flag = 1;
     }
 
+    pps->pps_loop_filter_across_slices_enabled_flag = 1;
+
     // Fill VAAPI parameter buffers.
 
     *vseq = (VAEncSequenceParameterBufferHEVC) {