mirror of
https://github.com/hajimehoshi/ebiten.git
synced 2024-09-20 05:12:18 +02:00
268 lines
8.0 KiB
Go
268 lines
8.0 KiB
Go
// Copyright 2017 The Ebiten Authors
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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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// +build !js
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package mp3
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import (
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"fmt"
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"io"
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)
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var mpeg1_scalefac_sizes = [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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func (f *frame) readMainL3() error {
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nch := f.numberOfChannels()
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// Calculate header audio data size
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framesize := (144*
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g_mpeg1_bitrates[f.header.layer][f.header.bitrate_index])/
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g_sampling_frequency[f.header.sampling_frequency] +
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f.header.padding_bit
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if framesize > 2000 {
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return fmt.Errorf("mp3: framesize = %d", framesize)
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}
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// Sideinfo is 17 bytes for one channel and 32 bytes for two
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sideinfo_size := 32
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if nch == 1 {
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sideinfo_size = 17
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}
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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 f.header.protection_bit == 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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// getMainBits function in the same way as the side info is.
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if err := getMainData(main_data_size, f.sideInfo.main_data_begin); err != nil {
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// This could be due to not enough data in reservoir
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return err
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}
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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 := getMainPos()
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// Number of bits in the bitstream for the bands
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slen1 := mpeg1_scalefac_sizes[f.sideInfo.scalefac_compress[gr][ch]][0]
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slen2 := mpeg1_scalefac_sizes[f.sideInfo.scalefac_compress[gr][ch]][1]
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if (f.sideInfo.win_switch_flag[gr][ch] != 0) && (f.sideInfo.block_type[gr][ch] == 2) {
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if f.sideInfo.mixed_block_flag[gr][ch] != 0 {
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for sfb := 0; sfb < 8; sfb++ {
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f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(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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f.mainData.scalefac_s[gr][ch][sfb][win] = getMainBits(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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f.mainData.scalefac_s[gr][ch][sfb][win] = getMainBits(nbits)
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}
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}
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}
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} else { // block_type == 0 if winswitch == 0
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// Scale factor bands 0-5
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if (f.sideInfo.scfsi[ch][0] == 0) || (gr == 0) {
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for sfb := 0; sfb < 6; sfb++ {
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f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen1)
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}
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} else if (f.sideInfo.scfsi[ch][0] == 1) && (gr == 1) {
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// Copy scalefactors from granule 0 to granule 1
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for sfb := 0; sfb < 6; sfb++ {
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f.mainData.scalefac_l[1][ch][sfb] = f.mainData.scalefac_l[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 (f.sideInfo.scfsi[ch][1] == 0) || (gr == 0) {
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for sfb := 6; sfb < 11; sfb++ {
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f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen1)
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}
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} else if (f.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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f.mainData.scalefac_l[1][ch][sfb] = f.mainData.scalefac_l[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 (f.sideInfo.scfsi[ch][2] == 0) || (gr == 0) {
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for sfb := 11; sfb < 16; sfb++ {
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f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen2)
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}
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} else if (f.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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f.mainData.scalefac_l[1][ch][sfb] = f.mainData.scalefac_l[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 (f.sideInfo.scfsi[ch][3] == 0) || (gr == 0) {
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for sfb := 16; sfb < 21; sfb++ {
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f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen2)
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}
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} else if (f.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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f.mainData.scalefac_l[1][ch][sfb] = f.mainData.scalefac_l[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 := f.readHuffman(part_2_start, gr, ch); err != nil {
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return 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 nil
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}
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type mainDataBytes struct {
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// Large static data
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vec [2 * 1024]int
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// Pointer into the reservoir
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ptr []int
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// Index into the current byte(0-7)
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idx int
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// Number of bytes in reservoir(0-1024)
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top int
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pos int
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}
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var theMainDataBytes mainDataBytes
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func getMainData(size int, begin int) error {
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if size > 1500 {
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return 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 begin > theMainDataBytes.top {
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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([]int, size)
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n := 0
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var err error
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for n < size && err == nil {
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nn, err2 := getBytes(buf)
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n += nn
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err = err2
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}
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if n < size {
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if err == io.EOF {
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return fmt.Errorf("mp3: unexpected EOF at getMainData")
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}
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return err
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}
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copy(theMainDataBytes.vec[theMainDataBytes.top:], buf[:n])
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// Set up pointers
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theMainDataBytes.ptr = theMainDataBytes.vec[0:]
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theMainDataBytes.pos = 0
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theMainDataBytes.idx = 0
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theMainDataBytes.top += size
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// TODO: Define a special error and enable to continue the next frame.
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return fmt.Errorf("mp3: frame can't be decoded")
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}
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// Copy data from previous frames
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copy(theMainDataBytes.vec[:begin], theMainDataBytes.vec[theMainDataBytes.top-begin:theMainDataBytes.top])
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// Read the main_data from file
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buf := make([]int, size)
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n := 0
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var err error
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for n < size && err == nil {
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nn, err2 := getBytes(buf)
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n += nn
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err = err2
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}
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if n < size {
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if err == io.EOF {
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return fmt.Errorf("mp3: unexpected EOF at getMainData")
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}
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return err
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}
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copy(theMainDataBytes.vec[begin:], buf[:n])
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// Set up pointers
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theMainDataBytes.ptr = theMainDataBytes.vec[0:]
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theMainDataBytes.pos = 0
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theMainDataBytes.idx = 0
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theMainDataBytes.top = begin + size
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return nil
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}
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func getMainBit() int {
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tmp := uint(theMainDataBytes.ptr[0]) >> (7 - uint(theMainDataBytes.idx))
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tmp &= 0x01
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theMainDataBytes.ptr = theMainDataBytes.ptr[(theMainDataBytes.idx+1)>>3:]
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theMainDataBytes.pos += (theMainDataBytes.idx + 1) >> 3
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theMainDataBytes.idx = (theMainDataBytes.idx + 1) & 0x07
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return int(tmp)
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}
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func getMainBits(num int) int {
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if num == 0 {
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return 0
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}
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// Form a word of the next four bytes
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b := make([]int, 4)
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for i := range b {
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if len(theMainDataBytes.ptr) > i {
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b[i] = theMainDataBytes.ptr[i]
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}
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}
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tmp := (uint32(b[0]) << 24) | (uint32(b[1]) << 16) | (uint32(b[2]) << 8) | (uint32(b[3]) << 0)
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// Remove bits already used
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tmp = tmp << uint(theMainDataBytes.idx)
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// Remove bits after the desired bits
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tmp = tmp >> (32 - uint(num))
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// Update pointers
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theMainDataBytes.ptr = theMainDataBytes.ptr[(theMainDataBytes.idx+num)>>3:]
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theMainDataBytes.pos += (theMainDataBytes.idx + num) >> 3
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theMainDataBytes.idx = (theMainDataBytes.idx + num) & 0x07
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return int(tmp)
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}
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func getMainPos() int {
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pos := theMainDataBytes.pos
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pos *= 8 // Multiply by 8 to get number of bits
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pos += theMainDataBytes.idx
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return pos
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}
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func setMainPos(bit_pos int) {
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theMainDataBytes.ptr = theMainDataBytes.vec[bit_pos>>3:]
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theMainDataBytes.pos = bit_pos >> 3
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theMainDataBytes.idx = bit_pos & 0x7
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}
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