mirror of
https://github.com/wader/fq.git
synced 2024-12-25 22:34:14 +03:00
651 lines
22 KiB
Go
651 lines
22 KiB
Go
package flac
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import (
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"encoding/binary"
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"math/bits"
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"github.com/wader/fq/format"
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"github.com/wader/fq/format/registry"
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"github.com/wader/fq/internal/num"
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"github.com/wader/fq/pkg/checksum"
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"github.com/wader/fq/pkg/decode"
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"github.com/wader/fq/pkg/scalar"
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)
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func init() {
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registry.MustRegister(decode.Format{
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Name: format.FLAC_FRAME,
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Description: "FLAC frame",
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DecodeFn: frameDecode,
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})
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}
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const (
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SampleRateStreaminfo = 0b0000
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)
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const (
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SampleSizeStreaminfo = 0b000
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)
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const (
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BlockingStrategyFixed = 0
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BlockingStrategyVariable = 1
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)
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var BlockingStrategyNames = scalar.UToSymStr{
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BlockingStrategyFixed: "fixed",
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BlockingStrategyVariable: "variable",
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}
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const (
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BlockSizeEndOfHeader8 = 0b0110
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BlockSizeEndOfHeader16 = 0b0111
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)
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const (
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SampeleRateEndOfHeader8 = 0b1100
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SampeleRateEndOfHeader16 = 0b1101
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SampeleRateEndOfHeader160 = 0b1110
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)
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const (
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SubframeConstant = "constant"
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SubframeVerbatim = "verbatim"
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SubframeFixed = "fixed"
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SubframeLPC = "lpc"
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SubframeReserved = "reserved"
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)
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const (
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ChannelLeftSide = 0b1000
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ChannelSideRight = 0b1001
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ChannelMidSide = 0b1010
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)
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const (
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ResidualCodingMethodRice = 0b00
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ResidualCodingMethodRice2 = 0b01
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)
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var ResidualCodingMethodMap = scalar.UToScalar{
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ResidualCodingMethodRice: scalar.S{Sym: uint64(4), Description: "rice"},
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ResidualCodingMethodRice2: scalar.S{Sym: uint64(5), Description: "rice2"},
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}
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// TODO: generic enough?
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func utf8Uint(d *decode.D) uint64 {
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n := d.U8()
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// leading ones, bit negate and count zeroes
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c := bits.LeadingZeros8(^uint8(n))
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// 0b0xxxxxxx 1 byte
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// 0b110xxxxx 2 byte
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// 0b1110xxxx 3 byte
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// 0b11110xxx 4 byte
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switch c {
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case 0:
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// nop
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case 2, 3, 4:
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n = n & ((1 << (8 - c - 1)) - 1)
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for i := 1; i < c; i++ {
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n = n<<6 | d.U8()&0x3f
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}
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default:
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d.Errorf("invalid UTF8Uint")
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}
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return n
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}
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// in argument is an optional FlacFrameIn struct with stream info
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func frameDecode(d *decode.D, in interface{}) interface{} {
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var inStreamInfo *format.FlacStreamInfo
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ffi, ok := in.(format.FlacFrameIn)
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if ok {
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inStreamInfo = &ffi.StreamInfo
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}
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frameStart := d.Pos()
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blockSize := 0
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channelAssignment := uint64(0)
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channels := 0
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sampleSize := 0
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sideChannelIndex := -1
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d.FieldStruct("header", func(d *decode.D) {
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// <14> 11111111111110
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d.FieldU14("sync", d.AssertU(0b11111111111110), scalar.Bin)
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// <1> Reserved
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// 0 : mandatory value
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// 1 : reserved for future use
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d.FieldU1("reserved0", d.AssertU(0))
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// <1> Blocking strategy:
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// 0 : fixed-blocksize stream; frame header encodes the frame number
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// 1 : variable-blocksize stream; frame header encodes the sample number
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blockingStrategy := d.FieldU1("blocking_strategy", BlockingStrategyNames)
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// <4> Block size in inter-channel samples:
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// 0000 : reserved
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// 0001 : 192 samples
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// 0010-0101 : 576 * (2^(n-2)) samples, i.e. 576/1152/2304/4608
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// 0110 : get 8 bit (blocksize-1) from end of header
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// 0111 : get 16 bit (blocksize-1) from end of header
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// 1000-1111 : 256 * (2^(n-8)) samples, i.e. 256/512/1024/2048/4096/8192/16384/32768
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var blockSizeMap = scalar.UToScalar{
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0b0000: {Description: "reserved"},
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0b0001: {Sym: uint64(192)},
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0b0010: {Sym: uint64(576)},
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0b0011: {Sym: uint64(1152)},
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0b0100: {Sym: uint64(2304)},
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0b0101: {Sym: uint64(4608)},
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0b0110: {Description: "end of header (8 bit)"},
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0b0111: {Description: "end of header (16 bit)"},
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0b1000: {Sym: uint64(256)},
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0b1001: {Sym: uint64(512)},
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0b1010: {Sym: uint64(1024)},
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0b1011: {Sym: uint64(2048)},
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0b1100: {Sym: uint64(4096)},
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0b1101: {Sym: uint64(8192)},
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0b1110: {Sym: uint64(16384)},
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0b1111: {Sym: uint64(32768)},
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}
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blockSizeS := d.FieldScalarU4("block_size", blockSizeMap, scalar.Bin)
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if blockSizeS.Sym != nil {
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blockSize = int(blockSizeS.SymU())
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}
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// <4> Sample rate:
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// 0000 : get from STREAMINFO metadata block
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// 0001 : 88.2kHz
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// 0010 : 176.4kHz
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// 0011 : 192kHz
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// 0100 : 8kHz
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// 0101 : 16kHz
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// 0110 : 22.05kHz
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// 0111 : 24kHz
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// 1000 : 32kHz
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// 1001 : 44.1kHz
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// 1010 : 48kHz
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// 1011 : 96kHz
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// 1100 : get 8 bit sample rate (in kHz) from end of header
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// 1101 : get 16 bit sample rate (in Hz) from end of header
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// 1110 : get 16 bit sample rate (in tens of Hz) from end of header
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// 1111 : invalid, to prevent sync-fooling string of 1s
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var sampleRateMap = scalar.UToScalar{
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0b0000: {Description: "from streaminfo"},
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0b0001: {Sym: uint64(88200)},
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0b0010: {Sym: uint64(176400)},
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0b0011: {Sym: uint64(192000)},
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0b0100: {Sym: uint64(8000)},
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0b0101: {Sym: uint64(16000)},
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0b0110: {Sym: uint64(22050)},
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0b0111: {Sym: uint64(24000)},
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0b1000: {Sym: uint64(32000)},
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0b1001: {Sym: uint64(44100)},
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0b1010: {Sym: uint64(48000)},
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0b1011: {Sym: uint64(96000)},
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0b1100: {Description: "end of header (8 bit*1000)"},
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0b1101: {Description: "end of header (16 bit)"},
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0b1110: {Description: "end of header (16 bit*10)"},
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0b1111: {Description: "invalid"},
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}
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sampleRateS := d.FieldScalarU4("sample_rate", sampleRateMap, scalar.Bin)
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switch sampleRateS.ActualU() {
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case SampleRateStreaminfo:
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if inStreamInfo == nil {
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d.Fatalf("streaminfo required for sample rate")
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}
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}
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// <4> Channel assignment
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// 0000-0111 : (number of independent channels)-1. Where defined, the channel order follows SMPTE/ITU-R recommendations. The assignments are as follows:
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// 1 channel: mono
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// 2 channels: left, right
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// 3 channels: left, right, center
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// 4 channels: front left, front right, back left, back right
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// 5 channels: front left, front right, front center, back/surround left, back/surround right
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// 6 channels: front left, front right, front center, LFE, back/surround left, back/surround right
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// 7 channels: front left, front right, front center, LFE, back center, side left, side right
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// 8 channels: front left, front right, front center, LFE, back left, back right, side left, side right
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// 1000 : left/side stereo: channel 0 is the left channel, channel 1 is the side(difference) channel
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// 1001 : right/side stereo: channel 0 is the side(difference) channel, channel 1 is the right channel
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// 1010 : mid/side stereo: channel 0 is the mid(average) channel, channel 1 is the side(difference) channel
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// 1011-1111 : reserved
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// TODO: extract to tables and cleanup
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var channelAssignmentMap = scalar.UToScalar{
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0: {Sym: uint64(1), Description: "mono"},
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1: {Sym: uint64(2), Description: "lr"},
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2: {Sym: uint64(3), Description: "lrc"},
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3: {Sym: uint64(4), Description: "fl,fr,bl,br"},
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4: {Sym: uint64(5), Description: "fl,fr,fc,back/surround left,back/surround right"},
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5: {Sym: uint64(6), Description: "fl,fr,fc,lfe,back/surround left,back/surround right"},
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6: {Sym: uint64(7), Description: "fl,fr,fc,lfe,back center,sl,sr"},
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7: {Sym: uint64(8), Description: "fl,fr,fc,lfe,back left,br,sl,sr"},
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0b1000: {Sym: uint64(2), Description: "left/side stereo"},
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0b1001: {Sym: uint64(2), Description: "right/side stereo"},
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0b1010: {Sym: uint64(2), Description: "mid/side stereo"},
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0b1011: {Sym: nil, Description: "reserved"},
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0b1100: {Sym: nil, Description: "reserved"},
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0b1101: {Sym: nil, Description: "reserved"},
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0b1111: {Sym: nil, Description: "reserved"},
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}
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channelAssignmentS := d.FieldScalarU4("channel_assignment", channelAssignmentMap)
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if channelAssignmentS.Sym == nil {
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d.Fatalf("unknown number of channels")
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}
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channelAssignment = channelAssignmentS.ActualU()
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channels = int(channelAssignmentS.SymU())
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switch channelAssignmentS.ActualU() {
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case ChannelLeftSide:
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sideChannelIndex = 1
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case ChannelSideRight:
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sideChannelIndex = 0
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case ChannelMidSide:
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sideChannelIndex = 1
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}
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if sideChannelIndex != -1 {
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d.FieldValueU("side_channel_index", uint64(sideChannelIndex))
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}
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// <3> Sample size in bits:
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// 000 : get from STREAMINFO metadata block
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// 001 : 8 bits per sample
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// 010 : 12 bits per sample
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// 011 : reserved
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// 100 : 16 bits per sample
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// 101 : 20 bits per sample
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// 110 : 24 bits per sample
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// 111 : reserved
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var sampleSizeMap = scalar.UToScalar{
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0b000: {Description: "from streaminfo"},
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0b001: {Sym: uint64(8)},
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0b010: {Sym: uint64(12)},
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0b011: {Description: "reserved"},
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0b100: {Sym: uint64(16)},
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0b101: {Sym: uint64(20)},
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0b110: {Sym: uint64(24)},
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0b111: {Description: "reserved"},
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}
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sampleSizeS := d.FieldScalarU3("sample_size", sampleSizeMap, scalar.Bin)
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switch sampleSizeS.ActualU() {
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case SampleSizeStreaminfo:
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if inStreamInfo == nil {
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d.Fatalf("streaminfo required for sample size")
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}
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sampleSize = int(inStreamInfo.BitPerSample)
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default:
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if sampleSizeS.Sym != nil {
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sampleSize = int(sampleSizeS.SymU())
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}
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}
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// <1> Reserved:
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// 0 : mandatory value
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// 1 : reserved for future use
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d.FieldU1("reserved1", d.AssertU(0))
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d.FieldStruct("end_of_header", func(d *decode.D) {
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// if(variable blocksize)
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// <8-56>:"UTF-8" coded sample number (decoded number is 36 bits) [4]
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// else
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// <8-48>:"UTF-8" coded frame number (decoded number is 31 bits) [4]
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// 0 : fixed-blocksize stream; frame header encodes the frame number
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// 1 : variable-blocksize stream; frame header encodes the sample number
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switch blockingStrategy {
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case BlockingStrategyVariable:
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d.FieldUFn("sample_number", utf8Uint)
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case BlockingStrategyFixed:
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d.FieldUFn("frame_number", utf8Uint)
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}
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// if(blocksize bits == 011x)
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// 8/16 bit (blocksize-1)
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// 0110 : get 8 bit (blocksize-1) from end of header
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// 0111 : get 16 bit (blocksize-1) from end of header
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switch blockSizeS.ActualU() {
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case BlockSizeEndOfHeader8:
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blockSize = int(d.FieldU8("block_size", scalar.UAdd(1)))
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case BlockSizeEndOfHeader16:
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blockSize = int(d.FieldU16("block_size", scalar.UAdd(1)))
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}
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// if(sample rate bits == 11xx)
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// 8/16 bit sample rate
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// 1100 : get 8 bit sample rate (in kHz) from end of header
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// 1101 : get 16 bit sample rate (in Hz) from end of header
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// 1110 : get 16 bit sample rate (in tens of Hz) from end of header
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switch sampleRateS.ActualU() {
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case SampeleRateEndOfHeader8:
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d.FieldUFn("sample_rate", func(d *decode.D) uint64 { return d.U8() * 1000 })
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case SampeleRateEndOfHeader16:
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d.FieldU16("sample_rate")
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case SampeleRateEndOfHeader160:
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d.FieldUFn("sample_rate", func(d *decode.D) uint64 { return d.U16() * 10 })
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}
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})
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headerCRC := &checksum.CRC{Bits: 8, Table: checksum.ATM8Table}
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d.MustCopy(headerCRC, d.BitBufRange(frameStart, d.Pos()-frameStart))
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d.FieldU8("crc", d.ValidateUBytes(headerCRC.Sum(nil)), scalar.Hex)
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})
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var channelSamples [][]int64
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d.FieldArray("subframes", func(d *decode.D) {
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for channelIndex := 0; channelIndex < channels; channelIndex++ {
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d.FieldStruct("subframe", func(d *decode.D) {
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// <1> Zero bit padding, to prevent sync-fooling string of 1s
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d.FieldU1("zero_bit", d.AssertU(0))
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// <6> Subframe type:
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// 000000 : SUBFRAME_CONSTANT
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// 000001 : SUBFRAME_VERBATIM
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// 00001x : reserved
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// 0001xx : reserved
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// 001xxx : if(xxx <= 4) SUBFRAME_FIXED, xxx=order ; else reserved
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// 01xxxx : reserved
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// 1xxxxx : SUBFRAME_LPC, xxxxx=order-1
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lpcOrder := -1
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var subframeTypeRangeMap = scalar.URangeToScalar{
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{Range: [2]uint64{0b000000, 0b000000}, S: scalar.S{Sym: SubframeConstant}},
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{Range: [2]uint64{0b000001, 0b000001}, S: scalar.S{Sym: SubframeVerbatim}},
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{Range: [2]uint64{0b000010, 0b000011}, S: scalar.S{Sym: SubframeReserved}},
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{Range: [2]uint64{0b000100, 0b000111}, S: scalar.S{Sym: SubframeReserved}},
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{Range: [2]uint64{0b001000, 0b001100}, S: scalar.S{Sym: SubframeFixed}},
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{Range: [2]uint64{0b001101, 0b001111}, S: scalar.S{Sym: SubframeReserved}},
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{Range: [2]uint64{0b010000, 0b011111}, S: scalar.S{Sym: SubframeReserved}},
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{Range: [2]uint64{0b100000, 0b111111}, S: scalar.S{Sym: SubframeLPC}},
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}
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subframeTypeS := d.FieldScalarU6("subframe_type", subframeTypeRangeMap, scalar.Bin)
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switch subframeTypeS.SymStr() {
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case SubframeFixed:
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lpcOrder = int(subframeTypeS.ActualU() & 0b111)
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case SubframeLPC:
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lpcOrder = int((subframeTypeS.ActualU() & 0b11111) + 1)
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}
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if lpcOrder != -1 {
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d.FieldValueU("lpc_order", uint64(lpcOrder))
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}
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// 'Wasted bits-per-sample' flag:
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// 0 : no wasted bits-per-sample in source subblock, k=0
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// 1 : k wasted bits-per-sample in source subblock, k-1 follows, unary coded; e.g. k=3 => 001 follows, k=7 => 0000001 follows.
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wastedBitsFlag := d.FieldU1("wasted_bits_flag")
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var wastedBitsK int
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if wastedBitsFlag != 0 {
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wastedBitsK = int(d.FieldUnary("wasted_bits_k", 0, scalar.UAdd(1)))
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}
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subframeSampleSize := sampleSize - wastedBitsK
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if subframeSampleSize < 0 {
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d.Fatalf("negative subframeSampleSize %d", subframeSampleSize)
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}
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// if channel is side, add en extra sample bit
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// https://github.com/xiph/flac/blob/37e675b777d4e0de53ac9ff69e2aea10d92e729c/src/libFLAC/stream_decoder.c#L2040
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if channelIndex == sideChannelIndex {
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subframeSampleSize++
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}
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d.FieldValueU("subframe_sample_size", uint64(subframeSampleSize))
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decodeWarmupSamples := func(samples []int64, n int, sampleSize int) {
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if len(samples) < n {
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d.Fatalf("decodeWarmupSamples outside block size")
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}
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d.FieldArray("warmup_samples", func(d *decode.D) {
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for i := 0; i < n; i++ {
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samples[i] = d.FieldS("value", sampleSize)
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}
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})
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}
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decodeResiduals := func(samples []int64) {
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samplesLen := len(samples)
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n := 0
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// <2> Residual coding method:
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// 00 : partitioned Rice coding with 4-bit Rice parameter; RESIDUAL_CODING_METHOD_PARTITIONED_RICE follows
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// 01 : partitioned Rice coding with 5-bit Rice parameter; RESIDUAL_CODING_METHOD_PARTITIONED_RICE2 follows
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// 10-11 : reserved
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var riceEscape int
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var riceBits int
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residualCodingMethod := d.FieldU2("residual_coding_method", scalar.UToScalar{
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0b00: scalar.S{Sym: uint64(4), Description: "rice"},
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0b01: scalar.S{Sym: uint64(5), Description: "rice2"},
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})
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switch residualCodingMethod {
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case ResidualCodingMethodRice:
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riceEscape = 0b1111
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riceBits = 4
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case ResidualCodingMethodRice2:
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riceEscape = 0b11111
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riceBits = 5
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}
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// <4> Partition order.
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partitionOrder := int(d.FieldU4("partition_order"))
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// There will be 2^order partitions.
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ricePartitions := 1 << partitionOrder
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d.FieldValueU("rice_partitions", uint64(ricePartitions))
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d.FieldArray("partitions", func(d *decode.D) {
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for i := 0; i < ricePartitions; i++ {
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d.FieldStruct("partition", func(d *decode.D) {
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// Encoding parameter:
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// <4(+5)> Encoding parameter:
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// 0000-1110 : Rice parameter.
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// 1111 : Escape code, meaning the partition is in unencoded binary form using n bits per sample; n follows as a 5-bit number.
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// Or:
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// <5(+5)> Encoding parameter:
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// 00000-11110 : Rice parameter.
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// 11111 : Escape code, meaning the partition is in unencoded binary form using n bits per sample; n follows as a 5-bit number.
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// Encoded residual. The number of samples (n) in the partition is determined as follows:
|
|
// if the partition order is zero, n = frame's blocksize - predictor order
|
|
// else if this is not the first partition of the subframe, n = (frame's blocksize / (2^partition order))
|
|
// else n = (frame's blocksize / (2^partition order)) - predictor order
|
|
var count int
|
|
if partitionOrder == 0 {
|
|
count = blockSize - lpcOrder
|
|
} else if i != 0 {
|
|
count = blockSize / ricePartitions
|
|
} else {
|
|
count = (blockSize / ricePartitions) - lpcOrder
|
|
}
|
|
|
|
d.FieldValueU("count", uint64(count))
|
|
|
|
riceParameter := int(d.FieldU("rice_parameter", riceBits))
|
|
|
|
if samplesLen < n+count {
|
|
d.Fatalf("decodeResiduals outside block size")
|
|
}
|
|
|
|
if riceParameter == riceEscape {
|
|
escapeSampleSize := int(d.FieldU5("escape_sample_size"))
|
|
d.FieldRawLen("samples", int64(count*escapeSampleSize))
|
|
} else {
|
|
samplesStart := d.Pos()
|
|
for j := 0; j < count; j++ {
|
|
high := d.Unary(0)
|
|
_ = high
|
|
low := d.U(riceParameter)
|
|
_ = low
|
|
samples[n] = num.ZigZag(high<<riceParameter | low)
|
|
n++
|
|
}
|
|
samplesStop := d.Pos()
|
|
d.RangeFn(samplesStart, samplesStop-samplesStart, func(d *decode.D) {
|
|
d.FieldRawLen("samples", d.BitsLeft())
|
|
})
|
|
}
|
|
})
|
|
}
|
|
})
|
|
}
|
|
|
|
// modifies input samples slice and returns it
|
|
decodeLPC := func(lpcOrder int, samples []int64, coeffs []int64, shift int64) {
|
|
for i := lpcOrder; i < len(samples); i++ {
|
|
r := int64(0)
|
|
for j := 0; j < len(coeffs); j++ {
|
|
c := coeffs[j]
|
|
s := samples[i-j-1]
|
|
r += c * s
|
|
}
|
|
samples[i] = samples[i] + (r >> shift)
|
|
}
|
|
}
|
|
|
|
var samples []int64
|
|
switch subframeTypeS.SymStr() {
|
|
case SubframeConstant:
|
|
samples = make([]int64, blockSize)
|
|
// <n> Unencoded constant value of the subblock, n = frame's bits-per-sample.
|
|
v := d.FieldS("value", subframeSampleSize)
|
|
for i := 0; i < blockSize; i++ {
|
|
samples[i] = v
|
|
}
|
|
case SubframeVerbatim:
|
|
samples = make([]int64, blockSize)
|
|
// <n*i> Unencoded subblock; n = frame's bits-per-sample, i = frame's blocksize.
|
|
// TODO: refactor into some kind of FieldBitBufLenFn?
|
|
d.RangeFn(d.Pos(), int64(blockSize*subframeSampleSize), func(d *decode.D) {
|
|
d.FieldRawLen("samples", d.BitsLeft())
|
|
})
|
|
|
|
for i := 0; i < blockSize; i++ {
|
|
samples[i] = d.S(subframeSampleSize)
|
|
}
|
|
case SubframeFixed:
|
|
samples = make([]int64, blockSize)
|
|
|
|
// <n> Unencoded warm-up samples (n = frame's bits-per-sample * predictor order).
|
|
decodeWarmupSamples(samples, lpcOrder, subframeSampleSize)
|
|
// Encoded residual
|
|
decodeResiduals(samples[lpcOrder:])
|
|
// http://www.hpl.hp.com/techreports/1999/HPL-1999-144.pdf
|
|
fixedCoeffs := [][]int64{
|
|
{},
|
|
{1},
|
|
{2, -1},
|
|
{3, -3, 1},
|
|
{4, -6, 4, -1},
|
|
}
|
|
coeffs := fixedCoeffs[lpcOrder]
|
|
decodeLPC(lpcOrder, samples, coeffs, 0)
|
|
case SubframeLPC:
|
|
samples = make([]int64, blockSize)
|
|
|
|
// <n> Unencoded warm-up samples (n = frame's bits-per-sample * lpc order).
|
|
decodeWarmupSamples(samples, lpcOrder, subframeSampleSize)
|
|
// <4> (Quantized linear predictor coefficients' precision in bits)-1 (1111 = invalid).
|
|
precision := int(d.FieldU4("precision", scalar.UAdd(1)))
|
|
// <5> Quantized linear predictor coefficient shift needed in bits (NOTE: this number is signed two's-complement).
|
|
shift := d.FieldS5("shift")
|
|
if shift < 0 {
|
|
d.Fatalf("negative LPC shift %d", shift)
|
|
}
|
|
// <n> Unencoded predictor coefficients (n = qlp coeff precision * lpc order) (NOTE: the coefficients are signed two's-complement).
|
|
var coeffs []int64
|
|
d.FieldArray("coefficients", func(d *decode.D) {
|
|
for i := 0; i < lpcOrder; i++ {
|
|
coeffs = append(coeffs, d.FieldS("value", precision))
|
|
}
|
|
})
|
|
// Encoded residual
|
|
decodeResiduals(samples[lpcOrder:])
|
|
decodeLPC(lpcOrder, samples, coeffs, shift)
|
|
}
|
|
|
|
if wastedBitsK != 0 {
|
|
for i := 0; i < len(samples); i++ {
|
|
samples[i] <<= wastedBitsK
|
|
}
|
|
}
|
|
|
|
channelSamples = append(channelSamples, samples)
|
|
})
|
|
}
|
|
})
|
|
|
|
// <?> Zero-padding to byte alignment.
|
|
d.FieldU("byte_align", d.ByteAlignBits(), d.AssertU(0))
|
|
// <16> CRC-16 (polynomial = x^16 + x^15 + x^2 + x^0, initialized with 0) of everything before the crc, back to and including the frame header sync code
|
|
footerCRC := &checksum.CRC{Bits: 16, Table: checksum.ANSI16Table}
|
|
d.MustCopy(footerCRC, d.BitBufRange(frameStart, d.Pos()-frameStart))
|
|
d.FieldRawLen("footer_crc", 16, d.ValidateBitBuf(footerCRC.Sum(nil)), scalar.RawHex)
|
|
|
|
streamSamples := len(channelSamples[0])
|
|
for j := 0; j < len(channelSamples); j++ {
|
|
if streamSamples > len(channelSamples[j]) {
|
|
d.Fatalf("different amount of samples in channels %d != %d", streamSamples, len(channelSamples[j]))
|
|
}
|
|
}
|
|
|
|
// Transform mid/side channels into left, right
|
|
// mid = (left + right)/2
|
|
// side = left - right
|
|
switch channelAssignment {
|
|
case ChannelLeftSide:
|
|
for i := 0; i < len(channelSamples[0]); i++ {
|
|
channelSamples[1][i] = channelSamples[0][i] - channelSamples[1][i]
|
|
}
|
|
case ChannelSideRight:
|
|
for i := 0; i < len(channelSamples[0]); i++ {
|
|
channelSamples[0][i] = channelSamples[1][i] + channelSamples[0][i]
|
|
}
|
|
case ChannelMidSide:
|
|
for i := 0; i < len(channelSamples[0]); i++ {
|
|
m := channelSamples[0][i]
|
|
s := channelSamples[1][i]
|
|
m = m<<1 | s&1
|
|
channelSamples[0][i] = (m + s) >> 1
|
|
channelSamples[1][i] = (m - s) >> 1
|
|
}
|
|
default:
|
|
// not stereo or no side channel
|
|
}
|
|
|
|
outSampleSize := sampleSize + (sampleSize % 8)
|
|
|
|
bytesPerSample := outSampleSize / 8
|
|
p := 0
|
|
le := binary.LittleEndian
|
|
|
|
interleavedSamplesBuf := ffi.SamplesBuf
|
|
interleavedSamplesBufLen := len(channelSamples) * streamSamples * bytesPerSample
|
|
// TODO: decode read buffer?
|
|
// reuse buffer if possible
|
|
if interleavedSamplesBuf == nil || len(interleavedSamplesBuf) < interleavedSamplesBufLen {
|
|
interleavedSamplesBuf = make([]byte, interleavedSamplesBufLen)
|
|
}
|
|
|
|
// TODO: speedup by using more cache friendly memory layout for samples
|
|
for i := 0; i < streamSamples; i++ {
|
|
for j := 0; j < len(channelSamples); j++ {
|
|
|
|
s := channelSamples[j][i]
|
|
switch outSampleSize {
|
|
case 8:
|
|
interleavedSamplesBuf[p] = byte(s)
|
|
case 16:
|
|
le.PutUint16(interleavedSamplesBuf[p:], uint16(s))
|
|
case 24:
|
|
interleavedSamplesBuf[p] = byte(s)
|
|
le.PutUint16(interleavedSamplesBuf[p+1:], uint16(s>>8))
|
|
case 32:
|
|
le.PutUint32(interleavedSamplesBuf[p:], uint32(s))
|
|
}
|
|
p += bytesPerSample
|
|
}
|
|
}
|
|
|
|
return format.FlacFrameOut{
|
|
SamplesBuf: interleavedSamplesBuf,
|
|
Samples: uint64(streamSamples),
|
|
Channels: channels,
|
|
BitsPerSample: outSampleSize,
|
|
}
|
|
}
|