ebiten/audio/mp3/read.go
2017-06-17 00:08:47 +09:00

204 lines
6.8 KiB
Go

// Copyright 2017 The Ebiten Authors
//
// 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.
// +build !js
package mp3
// #include "pdmp3.h"
//
// extern t_mpeg1_main_data g_main_data;
// extern t_mpeg1_side_info g_side_info;
// extern t_mpeg1_header g_frame_header;
import "C"
import (
"fmt"
)
func isHeader(header uint32) bool {
const C_SYNC = 0xffe00000
if (header & C_SYNC) != C_SYNC {
return false
}
// Bitrate must not be 15.
if (header & (0xf << 12)) == 0xf<<12 {
return false
}
// Sample Frequency must not be 3.
if (header & (3 << 10)) == 3<<10 {
return false
}
return true
}
//export Read_Header
func Read_Header() C.int {
/* Get the next four bytes from the bitstream */
b1 := uint32(Get_Byte())
b2 := uint32(Get_Byte())
b3 := uint32(Get_Byte())
b4 := uint32(Get_Byte())
/* If we got an End Of File condition we're done */
if (b1 == eof) || (b2 == eof) || (b3 == eof) || (b4 == eof) {
return C.ERROR
}
header := (b1 << 24) | (b2 << 16) | (b3 << 8) | (b4 << 0)
for !isHeader(uint32(header)) {
/* No,so scan the bitstream one byte at a time until we find it or EOF */
/* Shift the values one byte to the left */
b1 = b2
b2 = b3
b3 = b4
/* Get one new byte from the bitstream */
b4 = uint32(Get_Byte())
/* If we got an End Of File condition we're done */
if b4 == eof {
return C.ERROR
}
/* Make up the new header */
header = (b1 << 24) | (b2 << 16) | (b3 << 8) | (b4 << 0)
} /* while... */
/* If we get here we've found the sync word,and can decode the header
* which is in the low 20 bits of the 32-bit sync+header word. */
/* Decode the header */
C.g_frame_header.id = C.uint((header & 0x00180000) >> 19)
C.g_frame_header.layer = C.t_mpeg1_layer((header & 0x00060000) >> 17)
C.g_frame_header.protection_bit = C.uint((header & 0x00010000) >> 16)
C.g_frame_header.bitrate_index = C.uint((header & 0x0000f000) >> 12)
C.g_frame_header.sampling_frequency = C.uint((header & 0x00000c00) >> 10)
C.g_frame_header.padding_bit = C.uint((header & 0x00000200) >> 9)
C.g_frame_header.private_bit = C.uint((header & 0x00000100) >> 8)
C.g_frame_header.mode = C.t_mpeg1_mode((header & 0x000000c0) >> 6)
C.g_frame_header.mode_extension = C.uint((header & 0x00000030) >> 4)
C.g_frame_header.copyright = C.uint((header & 0x00000008) >> 3)
C.g_frame_header.original_or_copy = C.uint((header & 0x00000004) >> 2)
C.g_frame_header.emphasis = C.uint((header & 0x00000003) >> 0)
/* Check for invalid values and impossible combinations */
if C.g_frame_header.id != 3 {
g_error = fmt.Errorf("mp3: ID must be 3\nHeader word is 0x%08x at file pos %d",
header, C.Get_Filepos())
return C.ERROR
}
if C.g_frame_header.bitrate_index == 0 {
g_error = fmt.Errorf("mp3: Free bitrate format NIY!\nHeader word is 0x%08x at file pos %d",
header, Get_Filepos())
return C.ERROR
//exit(1);
}
if C.g_frame_header.bitrate_index == 15 {
g_error = fmt.Errorf("mp3: bitrate_index = 15 is invalid!\nHeader word is 0x%08x at file pos %d",
header, Get_Filepos())
return C.ERROR
}
if C.g_frame_header.sampling_frequency == 3 {
g_error = fmt.Errorf("mp3: sampling_frequency = 3 is invalid! Header word is 0x%08x at file pos %d",
header, Get_Filepos())
return C.ERROR
}
if C.g_frame_header.layer == 0 {
g_error = fmt.Errorf("mp3: layer = 0 is invalid! Header word is 0x%08x at file pos %d",
header, Get_Filepos())
return C.ERROR
}
C.g_frame_header.layer = 4 - C.g_frame_header.layer
return C.OK
}
func readHuffman(part_2_start, gr, ch int) error {
/* Check that there is any data to decode. If not,zero the array. */
if C.g_side_info.part2_3_length[gr][ch] == 0 {
for is_pos := 0; is_pos < 576; is_pos++ {
C.g_main_data.is[gr][ch][is_pos] = 0.0
}
return nil
}
/* Calculate bit_pos_end which is the index of the last bit for this part. */
bit_pos_end := part_2_start + int(C.g_side_info.part2_3_length[gr][ch]) - 1
/* Determine region boundaries */
region_1_start := 0
region_2_start := 0
if (C.g_side_info.win_switch_flag[gr][ch] == 1) && (C.g_side_info.block_type[gr][ch] == 2) {
region_1_start = 36 /* sfb[9/3]*3=36 */
region_2_start = 576 /* No Region2 for short block case. */
} else {
sfreq := C.g_frame_header.sampling_frequency
region_1_start =
sfBandIndicesSet[sfreq].l[C.g_side_info.region0_count[gr][ch]+1]
region_2_start =
sfBandIndicesSet[sfreq].l[C.g_side_info.region0_count[gr][ch]+
C.g_side_info.region1_count[gr][ch]+2]
}
/* Read big_values using tables according to region_x_start */
for is_pos := 0; is_pos < int(C.g_side_info.big_values[gr][ch])*2; is_pos++ {
table_num := 0
if is_pos < region_1_start {
table_num = int(C.g_side_info.table_select[gr][ch][0])
} else if is_pos < region_2_start {
table_num = int(C.g_side_info.table_select[gr][ch][1])
} else {
table_num = int(C.g_side_info.table_select[gr][ch][2])
}
/* Get next Huffman coded words */
x, y, _, _, err := huffmanDecode(table_num)
if err != nil {
return err
}
/* In the big_values area there are two freq lines per Huffman word */
C.g_main_data.is[gr][ch][is_pos] = C.float(x)
is_pos++
C.g_main_data.is[gr][ch][is_pos] = C.float(y)
}
/* Read small values until is_pos = 576 or we run out of huffman data */
table_num := int(C.g_side_info.count1table_select[gr][ch]) + 32
is_pos := int(C.g_side_info.big_values[gr][ch]) * 2
for ; (is_pos <= 572) && (int(Get_Main_Pos()) <= bit_pos_end); is_pos++ {
/* Get next Huffman coded words */
x, y, v, w, err := huffmanDecode(table_num)
if err != nil {
return err
}
C.g_main_data.is[gr][ch][is_pos] = C.float(v)
is_pos++
if is_pos >= 576 {
break
}
C.g_main_data.is[gr][ch][is_pos] = C.float(w)
is_pos++
if is_pos >= 576 {
break
}
C.g_main_data.is[gr][ch][is_pos] = C.float(x)
is_pos++
if is_pos >= 576 {
break
}
C.g_main_data.is[gr][ch][is_pos] = C.float(y)
}
/* Check that we didn't read past the end of this section */
if int(C.Get_Main_Pos()) > (bit_pos_end + 1) {
/* Remove last words read */
is_pos -= 4
}
/* Setup count1 which is the index of the first sample in the rzero reg. */
C.g_side_info.count1[gr][ch] = C.unsigned(is_pos)
/* Zero out the last part if necessary */
for ; /* is_pos comes from last for-loop */ is_pos < 576; is_pos++ {
C.g_main_data.is[gr][ch][is_pos] = 0.0
}
/* Set the bitpos to point to the next part to read */
C.Set_Main_Pos(C.unsigned(bit_pos_end) + 1)
return nil
}