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audio/mp3: Refactoring: readSideInfo (was readAudioL3) returns *mpeg1SideInfo

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This commit is contained in:
Hajime Hoshi 2017-06-18 17:37:46 +09:00
parent 80e6d4a175
commit 2767136947
6 changed files with 72 additions and 69 deletions
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9
audio/mp3/decode_notjs.go
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@ -28,16 +28,9 @@ var (
readerEOF bool readerEOF bool
) )
func (f *frame) numberOfChannels() int {
if f.header.mode == mpeg1ModeSingleChannel {
return 1
}
return 2
}
func (f *frame) decodeL3() []uint8 { func (f *frame) decodeL3() []uint8 {
out := make([]uint8, 576*4*2) out := make([]uint8, 576*4*2)
nch := f.numberOfChannels() nch := f.header.numberOfChannels()
for gr := 0; gr < 2; gr++ { for gr := 0; gr < 2; gr++ {
for ch := 0; ch < nch; ch++ { for ch := 0; ch < nch; ch++ {
f.l3Requantize(gr, ch) f.l3Requantize(gr, ch)

2
audio/mp3/l3.go
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@ -552,7 +552,7 @@ func (f *frame) l3SubbandSynthesis(gr int, ch int, out []uint8) {
u_vec := make([]float32, 512) u_vec := make([]float32, 512)
s_vec := make([]float32, 32) s_vec := make([]float32, 32)
nch := f.numberOfChannels() nch := f.header.numberOfChannels()
/* Setup the n_win windowing vector and the v_vec intermediate vector */ /* 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 */ for ss := 0; ss < 18; ss++ { /* Loop through 18 samples in 32 subbands */
for i := 1023; i > 63; i-- { /* Shift up the V vector */ for i := 1023; i > 63; i-- { /* Shift up the V vector */

4
audio/mp3/maindata.go
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@ -27,9 +27,9 @@ var mpeg1_scalefac_sizes = [16][2]int{
} }
func (f *frame) readMainL3() error { func (f *frame) readMainL3() error {
nch := f.numberOfChannels() nch := f.header.numberOfChannels()
// Calculate header audio data size // Calculate header audio data size
framesize := f.size() framesize := f.header.frameSize()
if framesize > 2000 { if framesize > 2000 {
return fmt.Errorf("mp3: framesize = %d", framesize) return fmt.Errorf("mp3: framesize = %d", framesize)
} }

4
audio/mp3/read.go
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@ -63,9 +63,11 @@ func (f *frame) readNextFrame() (*frame, error) {
return nil, fmt.Errorf("mp3: only layer3 (want %d; got %d) is supported!", mpeg1Layer3, nf.header.layer) return nil, fmt.Errorf("mp3: only layer3 (want %d; got %d) is supported!", mpeg1Layer3, nf.header.layer)
} }
// Get side info // Get side info
if err := nf.readAudioL3(); err != nil { s, err := readSideInfo(&nf.header)
if err != nil {
return nil, err return nil, err
} }
nf.sideInfo = s
// If there's not enough main data in the bit reservoir, // If there's not enough main data in the bit reservoir,
// signal to calling function so that decoding isn't done! // signal to calling function so that decoding isn't done!
// Get main data(scalefactors and Huffman coded frequency data) // Get main data(scalefactors and Huffman coded frequency data)

90
audio/mp3/sideinfo.go
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@ -21,35 +21,12 @@ import (
"io" "io"
) )
var mpeg1Bitrates = map[mpeg1Layer][15]int{ func readSideInfo(header *mpeg1FrameHeader) (*mpeg1SideInfo, error) {
mpeg1Layer1: { nch := header.numberOfChannels()
0, 32000, 64000, 96000, 128000, 160000, 192000, 224000,
256000, 288000, 320000, 352000, 384000, 416000, 448000,
},
mpeg1Layer2: {
0, 32000, 48000, 56000, 64000, 80000, 96000, 112000,
128000, 160000, 192000, 224000, 256000, 320000, 384000,
},
mpeg1Layer3: {
0, 32000, 40000, 48000, 56000, 64000, 80000, 96000,
112000, 128000, 160000, 192000, 224000, 256000, 320000,
},
}
var samplingFrequency = [3]int{44100, 48000, 32000}
func (f *frame) size() int {
return (144*mpeg1Bitrates[f.header.layer][f.header.bitrate_index])/
samplingFrequency[f.header.sampling_frequency] +
int(f.header.padding_bit)
}
func (f *frame) readAudioL3() error {
nch := f.numberOfChannels()
/* Calculate header audio data size */ /* Calculate header audio data size */
framesize := f.size() framesize := header.frameSize()
if framesize > 2000 { if framesize > 2000 {
return fmt.Errorf("mp3: framesize = %d\n", framesize) return nil, fmt.Errorf("mp3: framesize = %d\n", 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
@ -59,67 +36,68 @@ func (f *frame) readAudioL3() error {
/* 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 header.protection_bit == 0 {
main_data_size -= 2 main_data_size -= 2
} }
/* Read sideinfo from bitstream into buffer used by getSideBits() */ /* Read sideinfo from bitstream into buffer used by getSideBits() */
s, err := getSideinfo(sideinfo_size) s, err := getSideinfo(sideinfo_size)
if err != nil { if err != nil {
return err return nil, err
} }
/* Parse audio data */ /* Parse audio data */
/* Pointer to where we should start reading main data */ /* Pointer to where we should start reading main data */
f.sideInfo.main_data_begin = s.getSideBits(9) si := &mpeg1SideInfo{}
si.main_data_begin = s.getSideBits(9)
/* Get private bits. Not used for anything. */ /* Get private bits. Not used for anything. */
if f.header.mode == mpeg1ModeSingleChannel { if header.mode == mpeg1ModeSingleChannel {
f.sideInfo.private_bits = s.getSideBits(5) si.private_bits = s.getSideBits(5)
} else { } else {
f.sideInfo.private_bits = s.getSideBits(3) si.private_bits = s.getSideBits(3)
} }
/* Get scale factor selection information */ /* Get scale factor selection information */
for ch := 0; ch < nch; ch++ { for ch := 0; ch < nch; ch++ {
for scfsi_band := 0; scfsi_band < 4; scfsi_band++ { for scfsi_band := 0; scfsi_band < 4; scfsi_band++ {
f.sideInfo.scfsi[ch][scfsi_band] = s.getSideBits(1) si.scfsi[ch][scfsi_band] = s.getSideBits(1)
} }
} }
/* Get the rest of the side information */ /* Get the rest of the side information */
for gr := 0; gr < 2; gr++ { for gr := 0; gr < 2; gr++ {
for ch := 0; ch < nch; ch++ { for ch := 0; ch < nch; ch++ {
f.sideInfo.part2_3_length[gr][ch] = s.getSideBits(12) si.part2_3_length[gr][ch] = s.getSideBits(12)
f.sideInfo.big_values[gr][ch] = s.getSideBits(9) si.big_values[gr][ch] = s.getSideBits(9)
f.sideInfo.global_gain[gr][ch] = s.getSideBits(8) si.global_gain[gr][ch] = s.getSideBits(8)
f.sideInfo.scalefac_compress[gr][ch] = s.getSideBits(4) si.scalefac_compress[gr][ch] = s.getSideBits(4)
f.sideInfo.win_switch_flag[gr][ch] = s.getSideBits(1) si.win_switch_flag[gr][ch] = s.getSideBits(1)
if f.sideInfo.win_switch_flag[gr][ch] == 1 { if si.win_switch_flag[gr][ch] == 1 {
f.sideInfo.block_type[gr][ch] = s.getSideBits(2) si.block_type[gr][ch] = s.getSideBits(2)
f.sideInfo.mixed_block_flag[gr][ch] = s.getSideBits(1) si.mixed_block_flag[gr][ch] = s.getSideBits(1)
for region := 0; region < 2; region++ { for region := 0; region < 2; region++ {
f.sideInfo.table_select[gr][ch][region] = s.getSideBits(5) si.table_select[gr][ch][region] = s.getSideBits(5)
} }
for window := 0; window < 3; window++ { for window := 0; window < 3; window++ {
f.sideInfo.subblock_gain[gr][ch][window] = s.getSideBits(3) si.subblock_gain[gr][ch][window] = s.getSideBits(3)
} }
if (f.sideInfo.block_type[gr][ch] == 2) && (f.sideInfo.mixed_block_flag[gr][ch] == 0) { if (si.block_type[gr][ch] == 2) && (si.mixed_block_flag[gr][ch] == 0) {
f.sideInfo.region0_count[gr][ch] = 8 /* Implicit */ si.region0_count[gr][ch] = 8 /* Implicit */
} else { } else {
f.sideInfo.region0_count[gr][ch] = 7 /* Implicit */ si.region0_count[gr][ch] = 7 /* Implicit */
} }
/* The standard is wrong on this!!! */ /* Implicit */ /* The standard is wrong on this!!! */ /* Implicit */
f.sideInfo.region1_count[gr][ch] = 20 - f.sideInfo.region0_count[gr][ch] si.region1_count[gr][ch] = 20 - si.region0_count[gr][ch]
} else { } else {
for region := 0; region < 3; region++ { for region := 0; region < 3; region++ {
f.sideInfo.table_select[gr][ch][region] = s.getSideBits(5) si.table_select[gr][ch][region] = s.getSideBits(5)
} }
f.sideInfo.region0_count[gr][ch] = s.getSideBits(4) si.region0_count[gr][ch] = s.getSideBits(4)
f.sideInfo.region1_count[gr][ch] = s.getSideBits(3) si.region1_count[gr][ch] = s.getSideBits(3)
f.sideInfo.block_type[gr][ch] = 0 /* Implicit */ si.block_type[gr][ch] = 0 /* Implicit */
} }
f.sideInfo.preflag[gr][ch] = s.getSideBits(1) si.preflag[gr][ch] = s.getSideBits(1)
f.sideInfo.scalefac_scale[gr][ch] = s.getSideBits(1) si.scalefac_scale[gr][ch] = s.getSideBits(1)
f.sideInfo.count1table_select[gr][ch] = s.getSideBits(1) si.count1table_select[gr][ch] = s.getSideBits(1)
} }
} }
return nil return si, nil
} }
// A sideInfoBytes is a bit reservoir for side info // A sideInfoBytes is a bit reservoir for side info

32
audio/mp3/types.go
View File

@ -87,10 +87,40 @@ type frame struct {
prev *frame prev *frame
header mpeg1FrameHeader header mpeg1FrameHeader
sideInfo mpeg1SideInfo sideInfo *mpeg1SideInfo
mainData mpeg1MainData mainData mpeg1MainData
mainDataBytes *mainDataBytes mainDataBytes *mainDataBytes
store [2][32][18]float32 store [2][32][18]float32
v_vec [2][1024]float32 v_vec [2][1024]float32
} }
var mpeg1Bitrates = map[mpeg1Layer][15]int{
mpeg1Layer1: {
0, 32000, 64000, 96000, 128000, 160000, 192000, 224000,
256000, 288000, 320000, 352000, 384000, 416000, 448000,
},
mpeg1Layer2: {
0, 32000, 48000, 56000, 64000, 80000, 96000, 112000,
128000, 160000, 192000, 224000, 256000, 320000, 384000,
},
mpeg1Layer3: {
0, 32000, 40000, 48000, 56000, 64000, 80000, 96000,
112000, 128000, 160000, 192000, 224000, 256000, 320000,
},
}
var samplingFrequency = [3]int{44100, 48000, 32000}
func (h *mpeg1FrameHeader) frameSize() int {
return (144*mpeg1Bitrates[h.layer][h.bitrate_index])/
samplingFrequency[h.sampling_frequency] +
int(h.padding_bit)
}
func (h *mpeg1FrameHeader) numberOfChannels() int {
if h.mode == mpeg1ModeSingleChannel {
return 1
}
return 2
}