src/dsp/convolve.h

/*
 * Copyright 2019 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.
 */

#ifndef LIBGAV1_SRC_DSP_CONVOLVE_H_
#define LIBGAV1_SRC_DSP_CONVOLVE_H_

#include <cassert>

// Pull in LIBGAV1_DspXXX defines representing the implementation status
// of each function. The resulting value of each can be used by each module to
// determine whether an implementation is needed at compile time.
// IWYU pragma: begin_exports

// ARM:
#include "src/dsp/arm/convolve_neon.h"

// x86:
// Note includes should be sorted in logical order avx2/avx/sse4, etc.
// The order of includes is important as each tests for a superior version
// before setting the base.
// clang-format off
#include "src/dsp/x86/convolve_avx2.h"
#include "src/dsp/x86/convolve_sse4.h"
// clang-format on

// IWYU pragma: end_exports

namespace libgav1 {
namespace dsp {

// Initializes Dsp::convolve and Dsp::convolve_scale. This function is not
// thread-safe.
void ConvolveInit_C();

inline 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;
}

}  // namespace dsp
}  // namespace libgav1

#endif  // LIBGAV1_SRC_DSP_CONVOLVE_H_