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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;
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