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audio/mp3: Refactoring

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This commit is contained in:
Hajime Hoshi 2017-06-18 02:38:43 +09:00
parent 93c48e15c0
commit 3a55c2f805
1 changed files with 41 additions and 46 deletions
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87
audio/mp3/maindata.go
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@ -28,39 +28,38 @@ var mpeg1_scalefac_sizes = [16][2]int{
func (f *frame) readMainL3() error { func (f *frame) readMainL3() error {
nch := f.numberOfChannels() nch := f.numberOfChannels()
/* Calculate header audio data size */ // Calculate header audio data size
framesize := (144* framesize := (144*
g_mpeg1_bitrates[f.header.layer][f.header.bitrate_index])/ g_mpeg1_bitrates[f.header.layer][f.header.bitrate_index])/
g_sampling_frequency[f.header.sampling_frequency] + g_sampling_frequency[f.header.sampling_frequency] +
int(f.header.padding_bit) f.header.padding_bit
if framesize > 2000 { if framesize > 2000 {
return fmt.Errorf("mp3: framesize = %d", framesize) return fmt.Errorf("mp3: framesize = %d", framesize)
} }
/* Sideinfo is 17 bytes for one channel and 32 bytes for two */ // Sideinfo is 17 bytes for one channel and 32 bytes for two
sideinfo_size := 32 sideinfo_size := 32
if nch == 1 { if nch == 1 {
sideinfo_size = 17 sideinfo_size = 17
} }
/* Main data size is the rest of the frame,including ancillary data */ // Main data size is the rest of the frame,including ancillary data
main_data_size := framesize - sideinfo_size - 4 /* sync+header */ main_data_size := framesize - sideinfo_size - 4 // sync+header
/* CRC is 2 bytes */ // CRC is 2 bytes
if f.header.protection_bit == 0 { if f.header.protection_bit == 0 {
main_data_size -= 2 main_data_size -= 2
} }
/* Assemble main data buffer with data from this frame and the previous // Assemble main data buffer with data from this frame and the previous
* two frames. main_data_begin indicates how many bytes from previous // two frames. main_data_begin indicates how many bytes from previous
* frames that should be used. This buffer is later accessed by the // frames that should be used. This buffer is later accessed by the
* getMainBits function in the same way as the side info is. // getMainBits function in the same way as the side info is.
*/ if err := getMainData(main_data_size, f.sideInfo.main_data_begin); err != nil {
if err := getMainData(main_data_size, int(f.sideInfo.main_data_begin)); err != nil { // This could be due to not enough data in reservoir
/* This could be due to not enough data in reservoir */
return err return err
} }
for gr := 0; gr < 2; gr++ { for gr := 0; gr < 2; gr++ {
for ch := 0; ch < nch; ch++ { for ch := 0; ch < nch; ch++ {
part_2_start := getMainPos() part_2_start := getMainPos()
/* Number of bits in the bitstream for the bands */ // Number of bits in the bitstream for the bands
slen1 := mpeg1_scalefac_sizes[f.sideInfo.scalefac_compress[gr][ch]][0] slen1 := mpeg1_scalefac_sizes[f.sideInfo.scalefac_compress[gr][ch]][0]
slen2 := mpeg1_scalefac_sizes[f.sideInfo.scalefac_compress[gr][ch]][1] slen2 := mpeg1_scalefac_sizes[f.sideInfo.scalefac_compress[gr][ch]][1]
if (f.sideInfo.win_switch_flag[gr][ch] != 0) && (f.sideInfo.block_type[gr][ch] == 2) { if (f.sideInfo.win_switch_flag[gr][ch] != 0) && (f.sideInfo.block_type[gr][ch] == 2) {
@ -69,7 +68,7 @@ func (f *frame) readMainL3() error {
f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen1) f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen1)
} }
for sfb := 3; sfb < 12; sfb++ { for sfb := 3; sfb < 12; sfb++ {
/*slen1 for band 3-5,slen2 for 6-11*/ //slen1 for band 3-5,slen2 for 6-11
nbits := slen2 nbits := slen2
if sfb < 6 { if sfb < 6 {
nbits = slen1 nbits = slen1
@ -80,7 +79,7 @@ func (f *frame) readMainL3() error {
} }
} else { } else {
for sfb := 0; sfb < 12; sfb++ { for sfb := 0; sfb < 12; sfb++ {
/*slen1 for band 3-5,slen2 for 6-11*/ //slen1 for band 3-5,slen2 for 6-11
nbits := slen2 nbits := slen2
if sfb < 6 { if sfb < 6 {
nbits = slen1 nbits = slen1
@ -90,59 +89,59 @@ func (f *frame) readMainL3() error {
} }
} }
} }
} else { /* block_type == 0 if winswitch == 0 */ } else { // block_type == 0 if winswitch == 0
/* Scale factor bands 0-5 */ // Scale factor bands 0-5
if (f.sideInfo.scfsi[ch][0] == 0) || (gr == 0) { if (f.sideInfo.scfsi[ch][0] == 0) || (gr == 0) {
for sfb := 0; sfb < 6; sfb++ { for sfb := 0; sfb < 6; sfb++ {
f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen1) f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen1)
} }
} else if (f.sideInfo.scfsi[ch][0] == 1) && (gr == 1) { } else if (f.sideInfo.scfsi[ch][0] == 1) && (gr == 1) {
/* Copy scalefactors from granule 0 to granule 1 */ // Copy scalefactors from granule 0 to granule 1
for sfb := 0; sfb < 6; sfb++ { for sfb := 0; sfb < 6; sfb++ {
f.mainData.scalefac_l[1][ch][sfb] = f.mainData.scalefac_l[0][ch][sfb] f.mainData.scalefac_l[1][ch][sfb] = f.mainData.scalefac_l[0][ch][sfb]
} }
} }
/* Scale factor bands 6-10 */ // Scale factor bands 6-10
if (f.sideInfo.scfsi[ch][1] == 0) || (gr == 0) { if (f.sideInfo.scfsi[ch][1] == 0) || (gr == 0) {
for sfb := 6; sfb < 11; sfb++ { for sfb := 6; sfb < 11; sfb++ {
f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen1) f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen1)
} }
} else if (f.sideInfo.scfsi[ch][1] == 1) && (gr == 1) { } else if (f.sideInfo.scfsi[ch][1] == 1) && (gr == 1) {
/* Copy scalefactors from granule 0 to granule 1 */ // Copy scalefactors from granule 0 to granule 1
for sfb := 6; sfb < 11; sfb++ { for sfb := 6; sfb < 11; sfb++ {
f.mainData.scalefac_l[1][ch][sfb] = f.mainData.scalefac_l[0][ch][sfb] f.mainData.scalefac_l[1][ch][sfb] = f.mainData.scalefac_l[0][ch][sfb]
} }
} }
/* Scale factor bands 11-15 */ // Scale factor bands 11-15
if (f.sideInfo.scfsi[ch][2] == 0) || (gr == 0) { if (f.sideInfo.scfsi[ch][2] == 0) || (gr == 0) {
for sfb := 11; sfb < 16; sfb++ { for sfb := 11; sfb < 16; sfb++ {
f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen2) f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen2)
} }
} else if (f.sideInfo.scfsi[ch][2] == 1) && (gr == 1) { } else if (f.sideInfo.scfsi[ch][2] == 1) && (gr == 1) {
/* Copy scalefactors from granule 0 to granule 1 */ // Copy scalefactors from granule 0 to granule 1
for sfb := 11; sfb < 16; sfb++ { for sfb := 11; sfb < 16; sfb++ {
f.mainData.scalefac_l[1][ch][sfb] = f.mainData.scalefac_l[0][ch][sfb] f.mainData.scalefac_l[1][ch][sfb] = f.mainData.scalefac_l[0][ch][sfb]
} }
} }
/* Scale factor bands 16-20 */ // Scale factor bands 16-20
if (f.sideInfo.scfsi[ch][3] == 0) || (gr == 0) { if (f.sideInfo.scfsi[ch][3] == 0) || (gr == 0) {
for sfb := 16; sfb < 21; sfb++ { for sfb := 16; sfb < 21; sfb++ {
f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen2) f.mainData.scalefac_l[gr][ch][sfb] = getMainBits(slen2)
} }
} else if (f.sideInfo.scfsi[ch][3] == 1) && (gr == 1) { } else if (f.sideInfo.scfsi[ch][3] == 1) && (gr == 1) {
/* Copy scalefactors from granule 0 to granule 1 */ // Copy scalefactors from granule 0 to granule 1
for sfb := 16; sfb < 21; sfb++ { for sfb := 16; sfb < 21; sfb++ {
f.mainData.scalefac_l[1][ch][sfb] = f.mainData.scalefac_l[0][ch][sfb] f.mainData.scalefac_l[1][ch][sfb] = f.mainData.scalefac_l[0][ch][sfb]
} }
} }
} }
/* Read Huffman coded data. Skip stuffing bits. */ // Read Huffman coded data. Skip stuffing bits.
if err := f.readHuffman(part_2_start, gr, ch); err != nil { if err := f.readHuffman(part_2_start, gr, ch); err != nil {
return err return err
} }
} }
} }
/* The ancillary data is stored here,but we ignore it. */ // The ancillary data is stored here,but we ignore it.
return nil return nil
} }
@ -166,7 +165,7 @@ func getMainData(size int, begin int) error {
return fmt.Errorf("mp3: size = %d", size) return fmt.Errorf("mp3: size = %d", size)
} }
// Check that there's data available from previous frames if needed // Check that there's data available from previous frames if needed
if int(begin) > theMainDataBytes.top { if begin > theMainDataBytes.top {
// No,there is not, so we skip decoding this frame, but we have to // No,there is not, so we skip decoding this frame, but we have to
// read the main_data bits from the bitstream in case they are needed // read the main_data bits from the bitstream in case they are needed
// for decoding the next frame. // for decoding the next frame.
@ -185,7 +184,7 @@ func getMainData(size int, begin int) error {
return err return err
} }
copy(theMainDataBytes.vec[theMainDataBytes.top:], buf[:n]) copy(theMainDataBytes.vec[theMainDataBytes.top:], buf[:n])
/* Set up pointers */ // Set up pointers
theMainDataBytes.ptr = theMainDataBytes.vec[0:] theMainDataBytes.ptr = theMainDataBytes.vec[0:]
theMainDataBytes.pos = 0 theMainDataBytes.pos = 0
theMainDataBytes.idx = 0 theMainDataBytes.idx = 0
@ -193,11 +192,9 @@ func getMainData(size int, begin int) error {
// TODO: Define a special error and enable to continue the next frame. // TODO: Define a special error and enable to continue the next frame.
return fmt.Errorf("mp3: frame can't be decoded") return fmt.Errorf("mp3: frame can't be decoded")
} }
/* Copy data from previous frames */ // Copy data from previous frames
for i := 0; i < begin; i++ { copy(theMainDataBytes.vec[:begin], theMainDataBytes.vec[theMainDataBytes.top-begin:theMainDataBytes.top])
theMainDataBytes.vec[i] = theMainDataBytes.vec[theMainDataBytes.top-begin+i] // Read the main_data from file
}
/* Read the main_data from file */
buf := make([]int, size) buf := make([]int, size)
n := 0 n := 0
var err error var err error
@ -213,7 +210,7 @@ func getMainData(size int, begin int) error {
return err return err
} }
copy(theMainDataBytes.vec[begin:], buf[:n]) copy(theMainDataBytes.vec[begin:], buf[:n])
/* Set up pointers */ // Set up pointers
theMainDataBytes.ptr = theMainDataBytes.vec[0:] theMainDataBytes.ptr = theMainDataBytes.vec[0:]
theMainDataBytes.pos = 0 theMainDataBytes.pos = 0
theMainDataBytes.idx = 0 theMainDataBytes.idx = 0
@ -234,7 +231,7 @@ func getMainBits(num int) int {
if num == 0 { if num == 0 {
return 0 return 0
} }
/* Form a word of the next four bytes */ // Form a word of the next four bytes
b := make([]int, 4) b := make([]int, 4)
for i := range b { for i := range b {
if len(theMainDataBytes.ptr) > i { if len(theMainDataBytes.ptr) > i {
@ -243,30 +240,28 @@ func getMainBits(num int) int {
} }
tmp := (uint32(b[0]) << 24) | (uint32(b[1]) << 16) | (uint32(b[2]) << 8) | (uint32(b[3]) << 0) tmp := (uint32(b[0]) << 24) | (uint32(b[1]) << 16) | (uint32(b[2]) << 8) | (uint32(b[3]) << 0)
/* Remove bits already used */ // Remove bits already used
tmp = tmp << uint(theMainDataBytes.idx) tmp = tmp << uint(theMainDataBytes.idx)
/* Remove bits after the desired bits */ // Remove bits after the desired bits
tmp = tmp >> (32 - uint(num)) tmp = tmp >> (32 - uint(num))
/* Update pointers */ // Update pointers
theMainDataBytes.ptr = theMainDataBytes.ptr[(theMainDataBytes.idx+int(num))>>3:] theMainDataBytes.ptr = theMainDataBytes.ptr[(theMainDataBytes.idx+num)>>3:]
theMainDataBytes.pos += (theMainDataBytes.idx + num) >> 3 theMainDataBytes.pos += (theMainDataBytes.idx + num) >> 3
theMainDataBytes.idx = (theMainDataBytes.idx + num) & 0x07 theMainDataBytes.idx = (theMainDataBytes.idx + num) & 0x07
/* Done */
return int(tmp) return int(tmp)
} }
func getMainPos() int { func getMainPos() int {
pos := theMainDataBytes.pos pos := theMainDataBytes.pos
pos *= 8 /* Multiply by 8 to get number of bits */ pos *= 8 // Multiply by 8 to get number of bits
pos += theMainDataBytes.idx /* Add current bit index */ pos += theMainDataBytes.idx
return pos return pos
} }
func setMainPos(bit_pos int) { func setMainPos(bit_pos int) {
theMainDataBytes.ptr = theMainDataBytes.vec[bit_pos>>3:] theMainDataBytes.ptr = theMainDataBytes.vec[bit_pos>>3:]
theMainDataBytes.pos = int(bit_pos) >> 3 theMainDataBytes.pos = bit_pos >> 3
theMainDataBytes.idx = int(bit_pos) & 0x7 theMainDataBytes.idx = bit_pos & 0x7
} }