134 lines
4.2 KiB
Go
134 lines
4.2 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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"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/huffman"
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"github.com/hajimehoshi/go-mp3/internal/sideinfo"
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)
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func readHuffman(m *bits.Bits, header frameheader.FrameHeader, sideInfo *sideinfo.SideInfo, mainData *MainData, part_2_start, gr, ch int) error {
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// Check that there is any data to decode. If not, zero the array.
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if sideInfo.Part2_3Length[gr][ch] == 0 {
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for i := 0; i < consts.SamplesPerGr; i++ {
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mainData.Is[gr][ch][i] = 0.0
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}
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return nil
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}
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// Calculate bit_pos_end which is the index of the last bit for this part.
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bit_pos_end := part_2_start + sideInfo.Part2_3Length[gr][ch] - 1
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// Determine region boundaries
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region_1_start := 0
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region_2_start := 0
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if (sideInfo.WinSwitchFlag[gr][ch] == 1) && (sideInfo.BlockType[gr][ch] == 2) {
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region_1_start = 36 // sfb[9/3]*3=36
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region_2_start = consts.SamplesPerGr // No Region2 for short block case.
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} else {
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sfreq := header.SamplingFrequency()
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lsf := header.LowSamplingFrequency()
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l := consts.SfBandIndices[lsf][sfreq][consts.SfBandIndicesLong]
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i := sideInfo.Region0Count[gr][ch] + 1
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if i < 0 || len(l) <= i {
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// TODO: Better error messages (#3)
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return fmt.Errorf("mp3: readHuffman failed: invalid index i: %d", i)
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}
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region_1_start = l[i]
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j := sideInfo.Region0Count[gr][ch] + sideInfo.Region1Count[gr][ch] + 2
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if j < 0 || len(l) <= j {
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// TODO: Better error messages (#3)
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return fmt.Errorf("mp3: readHuffman failed: invalid index j: %d", j)
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}
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region_2_start = l[j]
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}
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// Read big_values using tables according to region_x_start
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for is_pos := 0; is_pos < sideInfo.BigValues[gr][ch]*2; is_pos++ {
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// #22
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if is_pos >= len(mainData.Is[gr][ch]) {
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return fmt.Errorf("mp3: is_pos was too big: %d", is_pos)
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}
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table_num := 0
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if is_pos < region_1_start {
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table_num = sideInfo.TableSelect[gr][ch][0]
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} else if is_pos < region_2_start {
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table_num = sideInfo.TableSelect[gr][ch][1]
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} else {
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table_num = sideInfo.TableSelect[gr][ch][2]
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}
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// Get next Huffman coded words
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x, y, _, _, err := huffman.Decode(m, table_num)
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if err != nil {
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return err
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}
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// In the big_values area there are two freq lines per Huffman word
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mainData.Is[gr][ch][is_pos] = float32(x)
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is_pos++
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mainData.Is[gr][ch][is_pos] = float32(y)
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}
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// Read small values until is_pos = 576 or we run out of huffman data
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// TODO: Is this comment wrong?
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table_num := sideInfo.Count1TableSelect[gr][ch] + 32
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is_pos := sideInfo.BigValues[gr][ch] * 2
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for is_pos <= 572 && m.BitPos() <= bit_pos_end {
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// Get next Huffman coded words
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x, y, v, w, err := huffman.Decode(m, table_num)
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if err != nil {
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return err
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}
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mainData.Is[gr][ch][is_pos] = float32(v)
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is_pos++
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if is_pos >= consts.SamplesPerGr {
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break
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}
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mainData.Is[gr][ch][is_pos] = float32(w)
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is_pos++
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if is_pos >= consts.SamplesPerGr {
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break
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}
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mainData.Is[gr][ch][is_pos] = float32(x)
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is_pos++
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if is_pos >= consts.SamplesPerGr {
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break
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}
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mainData.Is[gr][ch][is_pos] = float32(y)
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is_pos++
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}
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// Check that we didn't read past the end of this section
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if m.BitPos() > (bit_pos_end + 1) {
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// Remove last words read
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is_pos -= 4
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}
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if is_pos < 0 {
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is_pos = 0
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}
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// Setup count1 which is the index of the first sample in the rzero reg.
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sideInfo.Count1[gr][ch] = is_pos
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// Zero out the last part if necessary
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for is_pos < consts.SamplesPerGr {
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mainData.Is[gr][ch][is_pos] = 0.0
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is_pos++
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}
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// Set the bitpos to point to the next part to read
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m.SetPos(bit_pos_end + 1)
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return nil
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}
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