// Copyright 2017 Hajime Hoshi // // 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. package frame import ( "fmt" "io" "math" "github.com/hajimehoshi/go-mp3/internal/bits" "github.com/hajimehoshi/go-mp3/internal/consts" "github.com/hajimehoshi/go-mp3/internal/frameheader" "github.com/hajimehoshi/go-mp3/internal/imdct" "github.com/hajimehoshi/go-mp3/internal/maindata" "github.com/hajimehoshi/go-mp3/internal/sideinfo" ) var ( powtab34 = make([]float64, 8207) pretab = []float64{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 3, 3, 3, 2, 0} ) func init() { for i := range powtab34 { powtab34[i] = math.Pow(float64(i), 4.0/3.0) } } type Frame struct { header frameheader.FrameHeader sideInfo *sideinfo.SideInfo mainData *maindata.MainData mainDataBits *bits.Bits store [2][32][18]float32 v_vec [2][1024]float32 } type FullReader interface { ReadFull([]byte) (int, error) } func readCRC(source FullReader) error { buf := make([]byte, 2) if n, err := source.ReadFull(buf); n < 2 { if err == io.EOF { return &consts.UnexpectedEOF{"readCRC"} } return fmt.Errorf("mp3: error at readCRC: %v", err) } return nil } func Read(source FullReader, position int64, prev *Frame) (frame *Frame, startPosition int64, err error) { h, pos, err := frameheader.Read(source, position) if err != nil { return nil, 0, err } if h.ProtectionBit() == 0 { if err := readCRC(source); err != nil { return nil, 0, err } } if h.ID() == consts.Version2_5 { return nil, 0, fmt.Errorf("mp3: MPEG version 2.5 is not supported") } if h.Layer() != consts.Layer3 { return nil, 0, fmt.Errorf("mp3: only layer3 (want %d; got %d) is supported", consts.Layer3, h.Layer()) } si, err := sideinfo.Read(source, h) if err != nil { return nil, 0, err } // If there's not enough main data in the bit reservoir, // signal to calling function so that decoding isn't done! // Get main data (scalefactors and Huffman coded frequency data) var prevM *bits.Bits if prev != nil { prevM = prev.mainDataBits } md, mdb, err := maindata.Read(source, prevM, h, si) if err != nil { return nil, 0, err } nf := &Frame{ header: h, sideInfo: si, mainData: md, mainDataBits: mdb, } if prev != nil { nf.store = prev.store nf.v_vec = prev.v_vec } return nf, pos, nil } func (f *Frame) SamplingFrequency() (int, error) { return f.header.SamplingFrequencyValue() } func (f *Frame) Decode() []byte { out := make([]byte, f.header.BytesPerFrame()) nch := f.header.NumberOfChannels() for gr := 0; gr < f.header.Granules(); gr++ { for ch := 0; ch < nch; ch++ { f.requantize(gr, ch) f.reorder(gr, ch) } f.stereo(gr) for ch := 0; ch < nch; ch++ { f.antialias(gr, ch) f.hybridSynthesis(gr, ch) f.frequencyInversion(gr, ch) f.subbandSynthesis(gr, ch, out[consts.SamplesPerGr*4*gr:]) } } return out } func (f *Frame) requantizeProcessLong(gr, ch, is_pos, sfb int) { sf_mult := 0.5 if f.sideInfo.ScalefacScale[gr][ch] != 0 { sf_mult = 1.0 } pf_x_pt := float64(f.sideInfo.Preflag[gr][ch]) * pretab[sfb] idx := -(sf_mult * (float64(f.mainData.ScalefacL[gr][ch][sfb]) + pf_x_pt)) + 0.25*(float64(f.sideInfo.GlobalGain[gr][ch])-210) tmp1 := math.Pow(2.0, idx) tmp2 := 0.0 if f.mainData.Is[gr][ch][is_pos] < 0.0 { tmp2 = -powtab34[int(-f.mainData.Is[gr][ch][is_pos])] } else { tmp2 = powtab34[int(f.mainData.Is[gr][ch][is_pos])] } f.mainData.Is[gr][ch][is_pos] = float32(tmp1 * tmp2) } func (f *Frame) requantizeProcessShort(gr, ch, is_pos, sfb, win int) { sf_mult := 0.5 if f.sideInfo.ScalefacScale[gr][ch] != 0 { sf_mult = 1.0 } idx := -(sf_mult * float64(f.mainData.ScalefacS[gr][ch][sfb][win])) + 0.25*(float64(f.sideInfo.GlobalGain[gr][ch])-210.0- 8.0*float64(f.sideInfo.SubblockGain[gr][ch][win])) tmp1 := math.Pow(2.0, idx) tmp2 := 0.0 if f.mainData.Is[gr][ch][is_pos] < 0 { tmp2 = -powtab34[int(-f.mainData.Is[gr][ch][is_pos])] } else { tmp2 = powtab34[int(f.mainData.Is[gr][ch][is_pos])] } f.mainData.Is[gr][ch][is_pos] = float32(tmp1 * tmp2) } func getSfBandIndicesArray(header *frameheader.FrameHeader) ([]int, []int) { sfreq := header.SamplingFrequency() // Setup sampling frequency index lsf := header.LowSamplingFrequency() sfBandIndicesShort := consts.SfBandIndices[lsf][sfreq][consts.SfBandIndicesShort] sfBandIndicesLong := consts.SfBandIndices[lsf][sfreq][consts.SfBandIndicesLong] return sfBandIndicesLong, sfBandIndicesShort } func (f *Frame) requantize(gr int, ch int) { sfBandIndicesLong, sfBandIndicesShort := getSfBandIndicesArray(&f.header) // Determine type of block to process if f.sideInfo.WinSwitchFlag[gr][ch] == 1 && f.sideInfo.BlockType[gr][ch] == 2 { // Short blocks // Check if the first two subbands // (=2*18 samples = 8 long or 3 short sfb's) uses long blocks if f.sideInfo.MixedBlockFlag[gr][ch] != 0 { // 2 longbl. sb first // First process the 2 long block subbands at the start sfb := 0 next_sfb := sfBandIndicesLong[sfb+1] for i := 0; i < 36; i++ { if i == next_sfb { sfb++ next_sfb = sfBandIndicesLong[sfb+1] } f.requantizeProcessLong(gr, ch, i, sfb) } // And next the remaining,non-zero,bands which uses short blocks sfb = 3 next_sfb = sfBandIndicesShort[sfb+1] * 3 win_len := sfBandIndicesShort[sfb+1] - sfBandIndicesShort[sfb] for i := 36; i < int(f.sideInfo.Count1[gr][ch]); /* i++ done below! */ { // Check if we're into the next scalefac band if i == next_sfb { sfb++ next_sfb = sfBandIndicesShort[sfb+1] * 3 win_len = sfBandIndicesShort[sfb+1] - sfBandIndicesShort[sfb] } for win := 0; win < 3; win++ { for j := 0; j < win_len; j++ { f.requantizeProcessShort(gr, ch, i, sfb, win) i++ } } } } else { // Only short blocks sfb := 0 next_sfb := sfBandIndicesShort[sfb+1] * 3 win_len := sfBandIndicesShort[sfb+1] - sfBandIndicesShort[sfb] for i := 0; i < int(f.sideInfo.Count1[gr][ch]); /* i++ done below! */ { // Check if we're into the next scalefac band if i == next_sfb { sfb++ next_sfb = sfBandIndicesShort[sfb+1] * 3 win_len = sfBandIndicesShort[sfb+1] - sfBandIndicesShort[sfb] } for win := 0; win < 3; win++ { for j := 0; j < win_len; j++ { f.requantizeProcessShort(gr, ch, i, sfb, win) i++ } } } } } else { // Only long blocks sfb := 0 next_sfb := sfBandIndicesLong[sfb+1] for i := 0; i < int(f.sideInfo.Count1[gr][ch]); i++ { if i == next_sfb { sfb++ next_sfb = sfBandIndicesLong[sfb+1] } f.requantizeProcessLong(gr, ch, i, sfb) } } } func (f *Frame) reorder(gr int, ch int) { re := make([]float32, consts.SamplesPerGr) _, sfBandIndicesShort := getSfBandIndicesArray(&f.header) // Only reorder short blocks if (f.sideInfo.WinSwitchFlag[gr][ch] == 1) && (f.sideInfo.BlockType[gr][ch] == 2) { // Short blocks // Check if the first two subbands // (=2*18 samples = 8 long or 3 short sfb's) uses long blocks sfb := 0 // 2 longbl. sb first if f.sideInfo.MixedBlockFlag[gr][ch] != 0 { sfb = 3 } next_sfb := sfBandIndicesShort[sfb+1] * 3 win_len := sfBandIndicesShort[sfb+1] - sfBandIndicesShort[sfb] i := 36 if sfb == 0 { i = 0 } for i < consts.SamplesPerGr { // Check if we're into the next scalefac band if i == next_sfb { // Copy reordered data back to the original vector j := 3 * sfBandIndicesShort[sfb] copy(f.mainData.Is[gr][ch][j:j+3*win_len], re[0:3*win_len]) // Check if this band is above the rzero region,if so we're done if i >= f.sideInfo.Count1[gr][ch] { return } sfb++ next_sfb = sfBandIndicesShort[sfb+1] * 3 win_len = sfBandIndicesShort[sfb+1] - sfBandIndicesShort[sfb] } for win := 0; win < 3; win++ { // Do the actual reordering for j := 0; j < win_len; j++ { re[j*3+win] = f.mainData.Is[gr][ch][i] i++ } } } // Copy reordered data of last band back to original vector j := 3 * sfBandIndicesShort[12] copy(f.mainData.Is[gr][ch][j:j+3*win_len], re[0:3*win_len]) } } var ( isRatios = []float32{0.000000, 0.267949, 0.577350, 1.000000, 1.732051, 3.732051} ) func (f *Frame) stereoProcessIntensityLong(gr int, sfb int) { is_ratio_l := float32(0) is_ratio_r := float32(0) // Check that((is_pos[sfb]=scalefac) < 7) => no intensity stereo if is_pos := f.mainData.ScalefacL[gr][0][sfb]; is_pos < 7 { sfBandIndicesLong, _ := getSfBandIndicesArray(&f.header) sfb_start := sfBandIndicesLong[sfb] sfb_stop := sfBandIndicesLong[sfb+1] if is_pos == 6 { // tan((6*PI)/12 = PI/2) needs special treatment! is_ratio_l = 1.0 is_ratio_r = 0.0 } else { is_ratio_l = isRatios[is_pos] / (1.0 + isRatios[is_pos]) is_ratio_r = 1.0 / (1.0 + isRatios[is_pos]) } // Now decode all samples in this scale factor band for i := sfb_start; i < sfb_stop; i++ { f.mainData.Is[gr][0][i] *= is_ratio_l f.mainData.Is[gr][1][i] *= is_ratio_r } } } func (f *Frame) stereoProcessIntensityShort(gr int, sfb int) { is_ratio_l := float32(0) is_ratio_r := float32(0) _, sfBandIndicesShort := getSfBandIndicesArray(&f.header) // The window length win_len := sfBandIndicesShort[sfb+1] - sfBandIndicesShort[sfb] // The three windows within the band has different scalefactors for win := 0; win < 3; win++ { // Check that((is_pos[sfb]=scalefac) < 7) => no intensity stereo is_pos := f.mainData.ScalefacS[gr][0][sfb][win] if is_pos < 7 { sfb_start := sfBandIndicesShort[sfb]*3 + win_len*win sfb_stop := sfb_start + win_len if is_pos == 6 { // tan((6*PI)/12 = PI/2) needs special treatment! is_ratio_l = 1.0 is_ratio_r = 0.0 } else { is_ratio_l = isRatios[is_pos] / (1.0 + isRatios[is_pos]) is_ratio_r = 1.0 / (1.0 + isRatios[is_pos]) } // Now decode all samples in this scale factor band for i := sfb_start; i < sfb_stop; i++ { // https://github.com/technosaurus/PDMP3/issues/3 f.mainData.Is[gr][0][i] *= is_ratio_l f.mainData.Is[gr][1][i] *= is_ratio_r } } } } func (f *Frame) stereo(gr int) { if f.header.UseMSStereo() { // Determine how many frequency lines to transform i := 1 if f.sideInfo.Count1[gr][0] > f.sideInfo.Count1[gr][1] { i = 0 } max_pos := int(f.sideInfo.Count1[gr][i]) // Do the actual processing const invSqrt2 = math.Sqrt2 / 2 for i := 0; i < max_pos; i++ { left := (f.mainData.Is[gr][0][i] + f.mainData.Is[gr][1][i]) * invSqrt2 right := (f.mainData.Is[gr][0][i] - f.mainData.Is[gr][1][i]) * invSqrt2 f.mainData.Is[gr][0][i] = left f.mainData.Is[gr][1][i] = right } } if f.header.UseIntensityStereo() { sfBandIndicesLong, sfBandIndicesShort := getSfBandIndicesArray(&f.header) // First band that is intensity stereo encoded is first band scale factor // band on or above count1 frequency line. N.B.: Intensity stereo coding is // only done for higher subbands, but logic is here for lower subbands. // Determine type of block to process if (f.sideInfo.WinSwitchFlag[gr][0] == 1) && (f.sideInfo.BlockType[gr][0] == 2) { // Short blocks // Check if the first two subbands // (=2*18 samples = 8 long or 3 short sfb's) uses long blocks if f.sideInfo.MixedBlockFlag[gr][0] != 0 { // 2 longbl. sb first for sfb := 0; sfb < 8; sfb++ { // First process 8 sfb's at start // Is this scale factor band above count1 for the right channel? if sfBandIndicesLong[sfb] >= f.sideInfo.Count1[gr][1] { f.stereoProcessIntensityLong(gr, sfb) } } // And next the remaining bands which uses short blocks for sfb := 3; sfb < 12; sfb++ { // Is this scale factor band above count1 for the right channel? if sfBandIndicesShort[sfb]*3 >= f.sideInfo.Count1[gr][1] { f.stereoProcessIntensityShort(gr, sfb) } } } else { // Only short blocks for sfb := 0; sfb < 12; sfb++ { // Is this scale factor band above count1 for the right channel? if sfBandIndicesShort[sfb]*3 >= f.sideInfo.Count1[gr][1] { f.stereoProcessIntensityShort(gr, sfb) } } } } else { // Only long blocks for sfb := 0; sfb < 21; sfb++ { // Is this scale factor band above count1 for the right channel? if sfBandIndicesLong[sfb] >= f.sideInfo.Count1[gr][1] { f.stereoProcessIntensityLong(gr, sfb) } } } } } var ( cs = []float32{0.857493, 0.881742, 0.949629, 0.983315, 0.995518, 0.999161, 0.999899, 0.999993} ca = []float32{-0.514496, -0.471732, -0.313377, -0.181913, -0.094574, -0.040966, -0.014199, -0.003700} ) func (f *Frame) antialias(gr int, ch int) { // No antialiasing is done for short blocks if (f.sideInfo.WinSwitchFlag[gr][ch] == 1) && (f.sideInfo.BlockType[gr][ch] == 2) && (f.sideInfo.MixedBlockFlag[gr][ch]) == 0 { return } // Setup the limit for how many subbands to transform sblim := 32 if (f.sideInfo.WinSwitchFlag[gr][ch] == 1) && (f.sideInfo.BlockType[gr][ch] == 2) && (f.sideInfo.MixedBlockFlag[gr][ch] == 1) { sblim = 2 } // Do the actual antialiasing for sb := 1; sb < sblim; sb++ { for i := 0; i < 8; i++ { li := 18*sb - 1 - i ui := 18*sb + i lb := f.mainData.Is[gr][ch][li]*cs[i] - f.mainData.Is[gr][ch][ui]*ca[i] ub := f.mainData.Is[gr][ch][ui]*cs[i] + f.mainData.Is[gr][ch][li]*ca[i] f.mainData.Is[gr][ch][li] = lb f.mainData.Is[gr][ch][ui] = ub } } } func (f *Frame) hybridSynthesis(gr int, ch int) { // Loop through all 32 subbands for sb := 0; sb < 32; sb++ { // Determine blocktype for this subband bt := int(f.sideInfo.BlockType[gr][ch]) if (f.sideInfo.WinSwitchFlag[gr][ch] == 1) && (f.sideInfo.MixedBlockFlag[gr][ch] == 1) && (sb < 2) { bt = 0 } // Do the inverse modified DCT and windowing in := make([]float32, 18) for i := range in { in[i] = f.mainData.Is[gr][ch][sb*18+i] } rawout := imdct.Win(in, bt) // Overlapp add with stored vector into main_data vector for i := 0; i < 18; i++ { f.mainData.Is[gr][ch][sb*18+i] = rawout[i] + f.store[ch][sb][i] f.store[ch][sb][i] = rawout[i+18] } } } func (f *Frame) frequencyInversion(gr int, ch int) { for sb := 1; sb < 32; sb += 2 { for i := 1; i < 18; i += 2 { f.mainData.Is[gr][ch][sb*18+i] = -f.mainData.Is[gr][ch][sb*18+i] } } } var synthNWin = [64][32]float32{} func init() { for i := 0; i < 64; i++ { for j := 0; j < 32; j++ { synthNWin[i][j] = float32(math.Cos(float64((16+i)*(2*j+1)) * (math.Pi / 64.0))) } } } var synthDtbl = [512]float32{ 0.000000000, -0.000015259, -0.000015259, -0.000015259, -0.000015259, -0.000015259, -0.000015259, -0.000030518, -0.000030518, -0.000030518, -0.000030518, -0.000045776, -0.000045776, -0.000061035, -0.000061035, -0.000076294, -0.000076294, -0.000091553, -0.000106812, -0.000106812, -0.000122070, -0.000137329, -0.000152588, -0.000167847, -0.000198364, -0.000213623, -0.000244141, -0.000259399, -0.000289917, -0.000320435, -0.000366211, -0.000396729, -0.000442505, -0.000473022, -0.000534058, -0.000579834, -0.000625610, -0.000686646, -0.000747681, -0.000808716, -0.000885010, -0.000961304, -0.001037598, -0.001113892, -0.001205444, -0.001296997, -0.001388550, -0.001480103, -0.001586914, -0.001693726, -0.001785278, -0.001907349, -0.002014160, -0.002120972, -0.002243042, -0.002349854, -0.002456665, -0.002578735, -0.002685547, -0.002792358, -0.002899170, -0.002990723, -0.003082275, -0.003173828, 0.003250122, 0.003326416, 0.003387451, 0.003433228, 0.003463745, 0.003479004, 0.003479004, 0.003463745, 0.003417969, 0.003372192, 0.003280640, 0.003173828, 0.003051758, 0.002883911, 0.002700806, 0.002487183, 0.002227783, 0.001937866, 0.001617432, 0.001266479, 0.000869751, 0.000442505, -0.000030518, -0.000549316, -0.001098633, -0.001693726, -0.002334595, -0.003005981, -0.003723145, -0.004486084, -0.005294800, -0.006118774, -0.007003784, -0.007919312, -0.008865356, -0.009841919, -0.010848999, -0.011886597, -0.012939453, -0.014022827, -0.015121460, -0.016235352, -0.017349243, -0.018463135, -0.019577026, -0.020690918, -0.021789551, -0.022857666, -0.023910522, -0.024932861, -0.025909424, -0.026840210, -0.027725220, -0.028533936, -0.029281616, -0.029937744, -0.030532837, -0.031005859, -0.031387329, -0.031661987, -0.031814575, -0.031845093, -0.031738281, -0.031478882, 0.031082153, 0.030517578, 0.029785156, 0.028884888, 0.027801514, 0.026535034, 0.025085449, 0.023422241, 0.021575928, 0.019531250, 0.017257690, 0.014801025, 0.012115479, 0.009231567, 0.006134033, 0.002822876, -0.000686646, -0.004394531, -0.008316040, -0.012420654, -0.016708374, -0.021179199, -0.025817871, -0.030609131, -0.035552979, -0.040634155, -0.045837402, -0.051132202, -0.056533813, -0.061996460, -0.067520142, -0.073059082, -0.078628540, -0.084182739, -0.089706421, -0.095169067, -0.100540161, -0.105819702, -0.110946655, -0.115921021, -0.120697021, -0.125259399, -0.129562378, -0.133590698, -0.137298584, -0.140670776, -0.143676758, -0.146255493, -0.148422241, -0.150115967, -0.151306152, -0.151962280, -0.152069092, -0.151596069, -0.150497437, -0.148773193, -0.146362305, -0.143264771, -0.139450073, -0.134887695, -0.129577637, 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0.000213623, 0.000198364, 0.000167847, 0.000152588, 0.000137329, 0.000122070, 0.000106812, 0.000106812, 0.000091553, 0.000076294, 0.000076294, 0.000061035, 0.000061035, 0.000045776, 0.000045776, 0.000030518, 0.000030518, 0.000030518, 0.000030518, 0.000015259, 0.000015259, 0.000015259, 0.000015259, 0.000015259, 0.000015259, } func (f *Frame) subbandSynthesis(gr int, ch int, out []byte) { u_vec := make([]float32, 512) s_vec := make([]float32, 32) nch := f.header.NumberOfChannels() // Setup the n_win windowing vector and the v_vec intermediate vector for ss := 0; ss < 18; ss++ { // Loop through 18 samples in 32 subbands copy(f.v_vec[ch][64:1024], f.v_vec[ch][0:1024-64]) d := f.mainData.Is[gr][ch] for i := 0; i < 32; i++ { // Copy next 32 time samples to a temp vector s_vec[i] = d[i*18+ss] } for i := 0; i < 64; i++ { // Matrix multiply input with n_win[][] matrix sum := float32(0) for j := 0; j < 32; j++ { sum += synthNWin[i][j] * s_vec[j] } f.v_vec[ch][i] = sum } v := f.v_vec[ch] for i := 0; i < 512; i += 64 { // Build the U vector copy(u_vec[i:i+32], v[(i<<1):(i<<1)+32]) copy(u_vec[i+32:i+64], v[(i<<1)+96:(i<<1)+128]) } for i := 0; i < 512; i++ { // Window by u_vec[i] with synthDtbl[i] u_vec[i] *= synthDtbl[i] } for i := 0; i < 32; i++ { // Calc 32 samples,store in outdata vector sum := float32(0) for j := 0; j < 512; j += 32 { sum += u_vec[j+i] } // sum now contains time sample 32*ss+i. Convert to 16-bit signed int samp := int(sum * 32767) if samp > 32767 { samp = 32767 } else if samp < -32767 { samp = -32767 } s := int16(samp) idx := 4 * (32*ss + i) if nch == 1 { // We always run in stereo mode and duplicate channels here for mono. out[idx] = byte(s) out[idx+1] = byte(s >> 8) out[idx+2] = byte(s) out[idx+3] = byte(s >> 8) continue } if ch == 0 { out[idx] = byte(s) out[idx+1] = byte(s >> 8) } else { out[idx+2] = byte(s) out[idx+3] = byte(s >> 8) } } } }