305 lines
8.9 KiB
Go
305 lines
8.9 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 maindata
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import (
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"fmt"
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"io"
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"github.com/hajimehoshi/go-mp3/internal/bits"
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"github.com/hajimehoshi/go-mp3/internal/consts"
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"github.com/hajimehoshi/go-mp3/internal/frameheader"
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"github.com/hajimehoshi/go-mp3/internal/sideinfo"
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)
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type FullReader interface {
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ReadFull([]byte) (int, error)
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}
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// A MainData is MPEG1 Layer 3 Main Data.
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type MainData struct {
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ScalefacL [2][2][22]int // 0-4 bits
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ScalefacS [2][2][13][3]int // 0-4 bits
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Is [2][2][576]float32 // Huffman coded freq. lines
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}
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var scalefacSizesMpeg1 = [16][2]int{
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{0, 0}, {0, 1}, {0, 2}, {0, 3}, {3, 0}, {1, 1}, {1, 2}, {1, 3},
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{2, 1}, {2, 2}, {2, 3}, {3, 1}, {3, 2}, {3, 3}, {4, 2}, {4, 3},
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}
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var scalefacSizesMpeg2 = [3][6][4]int{
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{{6, 5, 5, 5}, {6, 5, 7, 3}, {11, 10, 0, 0},
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{7, 7, 7, 0}, {6, 6, 6, 3}, {8, 8, 5, 0}},
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{{9, 9, 9, 9}, {9, 9, 12, 6}, {18, 18, 0, 0},
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{12, 12, 12, 0}, {12, 9, 9, 6}, {15, 12, 9, 0}},
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{{6, 9, 9, 9}, {6, 9, 12, 6}, {15, 18, 0, 0},
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{6, 15, 12, 0}, {6, 12, 9, 6}, {6, 18, 9, 0}}}
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var nSlen2 = initSlen() /* MPEG 2.0 slen for 'normal' mode */
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func initSlen() (nSlen2 [512]int) {
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for i := 0; i < 4; i++ {
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for j := 0; j < 3; j++ {
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n := j + i*3
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nSlen2[n+500] = i | (j << 3) | (2 << 12) | (1 << 15)
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}
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}
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for i := 0; i < 5; i++ {
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for j := 0; j < 5; j++ {
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for k := 0; k < 4; k++ {
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for l := 0; l < 4; l++ {
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n := l + k*4 + j*16 + i*80
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nSlen2[n] = i | (j << 3) | (k << 6) | (l << 9) | (0 << 12)
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}
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}
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}
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}
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for i := 0; i < 5; i++ {
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for j := 0; j < 5; j++ {
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for k := 0; k < 4; k++ {
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n := k + j*4 + i*20
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nSlen2[n+400] = i | (j << 3) | (k << 6) | (1 << 12)
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}
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}
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}
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return
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}
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func Read(source FullReader, prev *bits.Bits, header frameheader.FrameHeader, sideInfo *sideinfo.SideInfo) (*MainData, *bits.Bits, error) {
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nch := header.NumberOfChannels()
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// Calculate header audio data size
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framesize, err := header.FrameSize()
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if err != nil {
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return nil, nil, err
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}
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if framesize > 2000 {
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return nil, nil, fmt.Errorf("mp3: framesize = %d", framesize)
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}
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sideinfo_size := header.SideInfoSize()
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// Main data size is the rest of the frame,including ancillary data
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main_data_size := framesize - sideinfo_size - 4 // sync+header
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// CRC is 2 bytes
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if header.ProtectionBit() == 0 {
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main_data_size -= 2
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}
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// Assemble main data buffer with data from this frame and the previous
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// two frames. main_data_begin indicates how many bytes from previous
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// frames that should be used. This buffer is later accessed by the
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// Bits function in the same way as the side info is.
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m, err := read(source, prev, main_data_size, sideInfo.MainDataBegin)
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if err != nil {
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// This could be due to not enough data in reservoir
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return nil, nil, err
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}
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if header.LowSamplingFrequency() == 1 {
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return getScaleFactorsMpeg2(m, header, sideInfo)
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}
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return getScaleFactorsMpeg1(nch, m, header, sideInfo)
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}
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func getScaleFactorsMpeg2(m *bits.Bits, header frameheader.FrameHeader, sideInfo *sideinfo.SideInfo) (*MainData, *bits.Bits, error) {
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nch := header.NumberOfChannels()
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md := &MainData{}
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for ch := 0; ch < nch; ch++ {
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part_2_start := m.BitPos()
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numbits := 0
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slen := nSlen2[sideInfo.ScalefacCompress[0][ch]]
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sideInfo.Preflag[0][ch] = (slen >> 15) & 0x1
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n := 0
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if sideInfo.BlockType[0][ch] == 2 {
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n++
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if sideInfo.MixedBlockFlag[0][ch] != 0 {
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n++
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}
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}
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var scaleFactors []int
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d := (slen >> 12) & 0x7
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for i := 0; i < 4; i++ {
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num := slen & 0x7
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slen >>= 3
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if num > 0 {
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for j := 0; j < scalefacSizesMpeg2[n][d][i]; j++ {
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scaleFactors = append(scaleFactors, m.Bits(num))
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}
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numbits += scalefacSizesMpeg2[n][d][i] * num
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} else {
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for j := 0; j < scalefacSizesMpeg2[n][d][i]; j++ {
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scaleFactors = append(scaleFactors, 0)
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}
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}
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}
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n = (n << 1) + 1
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for i := 0; i < n; i++ {
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scaleFactors = append(scaleFactors, 0)
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}
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if len(scaleFactors) == 22 {
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for i := 0; i < 22; i++ {
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md.ScalefacL[0][ch][i] = scaleFactors[i]
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}
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} else {
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for x := 0; x < 13; x++ {
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for i := 0; i < 3; i++ {
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md.ScalefacS[0][ch][x][i] = scaleFactors[(x*3)+i]
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}
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}
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}
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// Read Huffman coded data. Skip stuffing bits.
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if err := readHuffman(m, header, sideInfo, md, part_2_start, 0, ch); err != nil {
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return nil, nil, err
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}
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}
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// The ancillary data is stored here,but we ignore it.
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return md, m, nil
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}
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func getScaleFactorsMpeg1(nch int, m *bits.Bits, header frameheader.FrameHeader, sideInfo *sideinfo.SideInfo) (*MainData, *bits.Bits, error) {
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md := &MainData{}
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for gr := 0; gr < 2; gr++ {
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for ch := 0; ch < nch; ch++ {
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part_2_start := m.BitPos()
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// Number of bits in the bitstream for the bands
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slen1 := scalefacSizesMpeg1[sideInfo.ScalefacCompress[gr][ch]][0]
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slen2 := scalefacSizesMpeg1[sideInfo.ScalefacCompress[gr][ch]][1]
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if sideInfo.WinSwitchFlag[gr][ch] == 1 && sideInfo.BlockType[gr][ch] == 2 {
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if sideInfo.MixedBlockFlag[gr][ch] != 0 {
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for sfb := 0; sfb < 8; sfb++ {
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md.ScalefacL[gr][ch][sfb] = m.Bits(slen1)
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}
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for sfb := 3; sfb < 12; sfb++ {
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//slen1 for band 3-5,slen2 for 6-11
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nbits := slen2
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if sfb < 6 {
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nbits = slen1
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}
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for win := 0; win < 3; win++ {
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md.ScalefacS[gr][ch][sfb][win] = m.Bits(nbits)
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}
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}
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} else {
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for sfb := 0; sfb < 12; sfb++ {
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//slen1 for band 3-5,slen2 for 6-11
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nbits := slen2
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if sfb < 6 {
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nbits = slen1
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}
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for win := 0; win < 3; win++ {
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md.ScalefacS[gr][ch][sfb][win] = m.Bits(nbits)
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}
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}
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}
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} else {
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// Scale factor bands 0-5
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if sideInfo.Scfsi[ch][0] == 0 || gr == 0 {
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for sfb := 0; sfb < 6; sfb++ {
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md.ScalefacL[gr][ch][sfb] = m.Bits(slen1)
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}
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} else if sideInfo.Scfsi[ch][0] == 1 && gr == 1 {
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// Copy scalefactors from granule 0 to granule 1
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// TODO: This is not listed on the spec.
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for sfb := 0; sfb < 6; sfb++ {
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md.ScalefacL[1][ch][sfb] = md.ScalefacL[0][ch][sfb]
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}
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}
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// Scale factor bands 6-10
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if sideInfo.Scfsi[ch][1] == 0 || gr == 0 {
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for sfb := 6; sfb < 11; sfb++ {
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md.ScalefacL[gr][ch][sfb] = m.Bits(slen1)
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}
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} else if sideInfo.Scfsi[ch][1] == 1 && gr == 1 {
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// Copy scalefactors from granule 0 to granule 1
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for sfb := 6; sfb < 11; sfb++ {
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md.ScalefacL[1][ch][sfb] = md.ScalefacL[0][ch][sfb]
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}
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}
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// Scale factor bands 11-15
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if sideInfo.Scfsi[ch][2] == 0 || gr == 0 {
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for sfb := 11; sfb < 16; sfb++ {
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md.ScalefacL[gr][ch][sfb] = m.Bits(slen2)
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}
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} else if sideInfo.Scfsi[ch][2] == 1 && gr == 1 {
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// Copy scalefactors from granule 0 to granule 1
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for sfb := 11; sfb < 16; sfb++ {
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md.ScalefacL[1][ch][sfb] = md.ScalefacL[0][ch][sfb]
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}
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}
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// Scale factor bands 16-20
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if sideInfo.Scfsi[ch][3] == 0 || gr == 0 {
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for sfb := 16; sfb < 21; sfb++ {
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md.ScalefacL[gr][ch][sfb] = m.Bits(slen2)
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}
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} else if sideInfo.Scfsi[ch][3] == 1 && gr == 1 {
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// Copy scalefactors from granule 0 to granule 1
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for sfb := 16; sfb < 21; sfb++ {
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md.ScalefacL[1][ch][sfb] = md.ScalefacL[0][ch][sfb]
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}
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}
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}
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// Read Huffman coded data. Skip stuffing bits.
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if err := readHuffman(m, header, sideInfo, md, part_2_start, gr, ch); err != nil {
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return nil, nil, err
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}
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}
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}
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// The ancillary data is stored here,but we ignore it.
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return md, m, nil
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}
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func read(source FullReader, prev *bits.Bits, size int, offset int) (*bits.Bits, error) {
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if size > 1500 {
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return nil, fmt.Errorf("mp3: size = %d", size)
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}
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// Check that there's data available from previous frames if needed
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if prev != nil && offset > prev.LenInBytes() {
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// No, there is not, so we skip decoding this frame, but we have to
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// read the main_data bits from the bitstream in case they are needed
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// for decoding the next frame.
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buf := make([]byte, size)
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if n, err := source.ReadFull(buf); n < size {
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if err == io.EOF {
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return nil, &consts.UnexpectedEOF{"maindata.Read (1)"}
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}
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return nil, err
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}
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// TODO: Define a special error and enable to continue the next frame.
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return bits.Append(prev, buf), nil
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}
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// Copy data from previous frames
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vec := []byte{}
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if prev != nil {
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vec = prev.Tail(offset)
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}
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// Read the main_data from file
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buf := make([]byte, size)
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if n, err := source.ReadFull(buf); n < size {
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if err == io.EOF {
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return nil, &consts.UnexpectedEOF{"maindata.Read (2)"}
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}
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return nil, err
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}
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return bits.New(append(vec, buf...)), nil
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}
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