1 files changed, 50 insertions, 0 deletions
diff --git a/src/dsp/convolve.inc b/src/dsp/convolve.inc
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+++ b/src/dsp/convolve.inc
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+// Copyright 2020 The libgav1 Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Constants and utility functions used for convolve implementations.
+// This will be included inside an anonymous namespace on files where these are
+// necessary.
+
+int GetNumTapsInFilter(const int filter_index) {
+  if (filter_index < 2) {
+    // Despite the names these only use 6 taps.
+    // kInterpolationFilterEightTap
+    // kInterpolationFilterEightTapSmooth
+    return 6;
+  }
+
+  if (filter_index == 2) {
+    // kInterpolationFilterEightTapSharp
+    return 8;
+  }
+
+  if (filter_index == 3) {
+    // kInterpolationFilterBilinear
+    return 2;
+  }
+
+  assert(filter_index > 3);
+  // For small sizes (width/height <= 4) the large filters are replaced with 4
+  // tap options.
+  // If the original filters were |kInterpolationFilterEightTap| or
+  // |kInterpolationFilterEightTapSharp| then it becomes
+  // |kInterpolationFilterSwitchable|.
+  // If it was |kInterpolationFilterEightTapSmooth| then it becomes an unnamed 4
+  // tap filter.
+  return 4;
+}
+
+constexpr int kIntermediateStride = kMaxSuperBlockSizeInPixels;
+constexpr int kHorizontalOffset = 3;
+constexpr int kFilterIndexShift = 6;