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108 lines
2.6 KiB
Go
108 lines
2.6 KiB
Go
// Copyright 2017 Hajime Hoshi
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package imdct
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import (
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"math"
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)
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var imdctWinData = [4][36]float32{}
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func init() {
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for i := 0; i < 36; i++ {
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imdctWinData[0][i] = float32(math.Sin(math.Pi / 36 * (float64(i) + 0.5)))
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}
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for i := 0; i < 18; i++ {
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imdctWinData[1][i] = float32(math.Sin(math.Pi / 36 * (float64(i) + 0.5)))
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}
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for i := 18; i < 24; i++ {
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imdctWinData[1][i] = 1.0
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}
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for i := 24; i < 30; i++ {
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imdctWinData[1][i] = float32(math.Sin(math.Pi / 12 * (float64(i) + 0.5 - 18.0)))
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}
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for i := 30; i < 36; i++ {
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imdctWinData[1][i] = 0.0
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}
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for i := 0; i < 12; i++ {
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imdctWinData[2][i] = float32(math.Sin(math.Pi / 12 * (float64(i) + 0.5)))
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}
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for i := 12; i < 36; i++ {
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imdctWinData[2][i] = 0.0
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}
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for i := 0; i < 6; i++ {
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imdctWinData[3][i] = 0.0
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}
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for i := 6; i < 12; i++ {
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imdctWinData[3][i] = float32(math.Sin(math.Pi / 12 * (float64(i) + 0.5 - 6.0)))
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}
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for i := 12; i < 18; i++ {
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imdctWinData[3][i] = 1.0
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}
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for i := 18; i < 36; i++ {
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imdctWinData[3][i] = float32(math.Sin(math.Pi / 36 * (float64(i) + 0.5)))
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}
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}
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var cosN12 = [6][12]float32{}
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func init() {
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const N = 12
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for i := 0; i < 6; i++ {
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for j := 0; j < 12; j++ {
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cosN12[i][j] = float32(math.Cos(math.Pi / (2 * N) * (2*float64(j) + 1 + N/2) * (2*float64(i) + 1)))
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}
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}
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}
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var cosN36 = [18][36]float32{}
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func init() {
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const N = 36
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for i := 0; i < 18; i++ {
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for j := 0; j < 36; j++ {
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cosN36[i][j] = float32(math.Cos(math.Pi / (2 * N) * (2*float64(j) + 1 + N/2) * (2*float64(i) + 1)))
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}
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}
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}
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func Win(in []float32, blockType int) []float32 {
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out := make([]float32, 36)
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if blockType == 2 {
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iwd := imdctWinData[blockType]
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const N = 12
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for i := 0; i < 3; i++ {
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for p := 0; p < N; p++ {
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sum := float32(0.0)
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for m := 0; m < N/2; m++ {
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sum += in[i+3*m] * cosN12[m][p]
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}
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out[6*i+p+6] += sum * iwd[p]
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}
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}
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return out
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}
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const N = 36
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iwd := imdctWinData[blockType]
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for p := 0; p < N; p++ {
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sum := float32(0.0)
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for m := 0; m < N/2; m++ {
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sum += in[m] * cosN36[m][p]
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}
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out[p] = sum * iwd[p]
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}
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return out
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}
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