mirror of
https://github.com/wader/fq.git
synced 2024-11-24 03:05:22 +03:00
672 lines
22 KiB
Go
672 lines
22 KiB
Go
package flac
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import (
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"encoding/binary"
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"fmt"
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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/crc"
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"github.com/wader/fq/pkg/decode"
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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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BlockingStrategyFixed = iota
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BlockingStrategyVariable
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)
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var BlockingStrategyNames = map[uint]string{
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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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SubframeConstant = iota
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SubframeVerbatim
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SubframeFixed
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SubframeLPC
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)
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var SubframeTypeNames = map[uint]string{
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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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}
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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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// 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.Invalid("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.FlacMetadatablockStreamInfo
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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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var channels uint64
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sampleSize := 0
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blockSize := 0
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channelAssignment := -1
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sideChannelIndex := -1
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d.FieldStructFn("header", func(d *decode.D) {
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// <14> 11111111111110
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d.FieldValidateUFn("sync", 0b11111111111110, d.U14)
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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.FieldValidateUFn("reserved0", 0, d.U1)
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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.FieldUFn("blocking_strategy", func() (uint64, decode.DisplayFormat, string) {
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switch d.U1() {
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case 0:
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return BlockingStrategyFixed, decode.NumberDecimal, BlockingStrategyNames[BlockingStrategyFixed]
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default:
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return BlockingStrategyVariable, decode.NumberDecimal, BlockingStrategyNames[BlockingStrategyVariable]
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}
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})
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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 blockSizeBits uint64
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blockSize = int(d.FieldUFn("block_size", func() (uint64, decode.DisplayFormat, string) {
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blockSizeBits = d.U4()
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switch blockSizeBits {
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case 0b0000:
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return 0, decode.NumberDecimal, "reserved"
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case 0b0001:
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return 192, decode.NumberDecimal, ""
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case 0b0010, 0b0011, 0b0100, 0b0101:
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return 576 * (1 << (blockSizeBits - 2)), decode.NumberDecimal, ""
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case 0b0110:
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return 0, decode.NumberDecimal, "end of header (8 bit)"
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case 0b0111:
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return 0, decode.NumberDecimal, "end of header (16 bit)"
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default:
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return 256 * (1 << (blockSizeBits - 8)), decode.NumberDecimal, ""
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}
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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 sampleRateBits uint64
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d.FieldUFn("sample_rate", func() (uint64, decode.DisplayFormat, string) {
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sampleRateBits = d.U4()
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switch sampleRateBits {
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case 0:
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if inStreamInfo == nil {
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d.Invalid("streaminfo required for sample rate")
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}
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return inStreamInfo.SampleRate, decode.NumberDecimal, "streaminfo"
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case 0b0001:
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return 88200, decode.NumberDecimal, ""
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case 0b0010:
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return 176000, decode.NumberDecimal, ""
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case 0b0011:
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return 19200, decode.NumberDecimal, ""
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case 0b0100:
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return 800, decode.NumberDecimal, ""
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case 0b0101:
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return 1600, decode.NumberDecimal, ""
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case 0b0110:
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return 22050, decode.NumberDecimal, ""
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case 0b0111:
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return 44100, decode.NumberDecimal, ""
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case 0b1000:
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return 32000, decode.NumberDecimal, ""
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case 0b1001:
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return 44100, decode.NumberDecimal, ""
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case 0b1010:
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return 48000, decode.NumberDecimal, ""
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case 0b1011:
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return 96000, decode.NumberDecimal, ""
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case 0b1100:
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return 0, decode.NumberDecimal, "end of header (8 bit*1000)"
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case 0b1101:
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return 0, decode.NumberDecimal, "end of header (16 bit)"
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case 0b1110:
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return 0, decode.NumberDecimal, "end of header (16 bit*10)"
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default:
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return 0, decode.NumberDecimal, "invalid"
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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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channels = d.FieldUFn("channel_assignment", func() (uint64, decode.DisplayFormat, string) {
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ca, u, disp := func() (uint64, uint64, string) {
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v := d.U4()
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switch v {
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case 0:
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return v, 1, "mono"
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case 1:
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return v, 2, "left, right"
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case 2:
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return v, 3, "left, right, center"
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case 3:
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return v, 4, "front left, front right, back left, back right"
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case 4:
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return v, 5, "front left, front right, front center, back/surround left, back/surround right"
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case 5:
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return v, 6, "front left, front right, front center, LFE, back/surround left, back/surround right"
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case 6:
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return v, 7, "front left, front right, front center, LFE, back center, side left, side right"
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case 7:
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return v, 8, "front left, front right, front center, LFE, back left, back right, side left, side right"
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case 0b1000:
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sideChannelIndex = 1
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return v, 2, "left/side"
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case 0b1001:
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sideChannelIndex = 0
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return v, 2, "side/right"
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case 0b1010:
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sideChannelIndex = 1
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return v, 2, "mid/side"
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default:
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return v, 0, "reserved"
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}
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}()
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channelAssignment = int(ca)
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if sideChannelIndex != -1 {
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d.FieldUFn("side_channel_index", func() (uint64, decode.DisplayFormat, string) {
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return uint64(sideChannelIndex), decode.NumberDecimal, ""
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})
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}
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return u, decode.NumberDecimal, disp
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})
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if channels == 0 {
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d.Invalid("unknown number of channels")
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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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sampleSize = int(d.FieldUFn("sample_size", func() (uint64, decode.DisplayFormat, string) {
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switch d.U3() {
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case 0b000:
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if inStreamInfo == nil {
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d.Invalid("streaminfo required for bit per sample")
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}
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return inStreamInfo.BitPerSample, decode.NumberDecimal, "streaminfo"
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case 0b001:
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return 8, decode.NumberDecimal, ""
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case 0b010:
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return 12, decode.NumberDecimal, ""
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case 0b011:
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return 0, decode.NumberDecimal, "reserved"
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case 0b100:
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return 16, decode.NumberDecimal, ""
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case 0b101:
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return 20, decode.NumberDecimal, ""
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case 0b110:
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return 24, decode.NumberDecimal, ""
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case 0b111:
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return 0, decode.NumberDecimal, "reserved"
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}
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panic("unreachable")
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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.FieldValidateUFn("reserved1", 0, d.U1)
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d.FieldStructFn("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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switch blockingStrategy {
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case BlockingStrategyVariable:
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d.FieldUFn("sample_number", func() (uint64, decode.DisplayFormat, string) {
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return utf8Uint(d), decode.NumberDecimal, ""
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})
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case BlockingStrategyFixed:
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d.FieldUFn("frame_number", func() (uint64, decode.DisplayFormat, string) {
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return utf8Uint(d), decode.NumberDecimal, ""
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})
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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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switch blockSizeBits {
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case 0b0110:
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blockSize = int(d.FieldUFn("block_size", func() (uint64, decode.DisplayFormat, string) {
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return d.U8() + 1, decode.NumberDecimal, ""
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}))
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case 0b0111:
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blockSize = int(d.FieldUFn("block_size", func() (uint64, decode.DisplayFormat, string) {
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return d.U16() + 1, decode.NumberDecimal, ""
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}))
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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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switch sampleRateBits {
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case 0b1100:
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d.FieldUFn("sample_rate", func() (uint64, decode.DisplayFormat, string) {
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return d.U8() * 1000, decode.NumberDecimal, ""
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})
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case 0b1101:
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d.FieldUFn("sample_rate", func() (uint64, decode.DisplayFormat, string) {
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return d.U16(), decode.NumberDecimal, ""
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})
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case 0b1110:
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d.FieldUFn("sample_rate", func() (uint64, decode.DisplayFormat, string) {
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return d.U16() * 10, decode.NumberDecimal, ""
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})
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case 0b1111:
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// TODO: reserved?
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}
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})
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headerCRC := &crc.CRC{Bits: 8, Table: crc.ATM8Table}
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decode.MustCopy(d, headerCRC, d.BitBufRange(frameStart, d.Pos()-frameStart))
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d.FieldChecksumLen("crc", 8, headerCRC.Sum(nil), decode.BigEndian)
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})
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var channelSamples [][]int64
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d.FieldArrayFn("subframes", func(d *decode.D) {
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for channelIndex := 0; channelIndex < int(channels); channelIndex++ {
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d.FieldStructFn("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.FieldValidateUFn("zero_bit", 0, d.U1)
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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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var lpcOrder int
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subframeType := d.FieldUFn("subframe_type", func() (uint64, decode.DisplayFormat, string) {
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u, disp := func() (uint64, string) {
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bits := d.U6()
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switch bits {
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case 0b000000:
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return SubframeConstant, SubframeTypeNames[SubframeConstant]
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case 0b000001:
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return SubframeVerbatim, SubframeTypeNames[SubframeVerbatim]
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case 0b001000, 0b001001, 0b001010, 0b001011, 0b001100:
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lpcOrder = int(bits & 0x7)
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return SubframeFixed, SubframeTypeNames[SubframeFixed]
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default:
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if bits&0x20 > 0 {
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lpcOrder = int((bits & 0x1f) + 1)
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} else {
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return 0, "reserved"
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}
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return SubframeLPC, SubframeTypeNames[SubframeLPC]
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}
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}()
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d.FieldUFn("lpc_order", func() (uint64, decode.DisplayFormat, string) {
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return uint64(lpcOrder), decode.NumberDecimal, ""
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})
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return u, decode.NumberDecimal, disp
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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.FieldUFn("wasted_bits_k", func() (uint64, decode.DisplayFormat, string) {
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return d.Unary(0) + 1, decode.NumberDecimal, ""
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}))
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}
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subframeSampleSize := sampleSize - wastedBitsK
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if subframeSampleSize < 0 {
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d.Invalid(fmt.Sprintf("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.Invalid("decodeWarmupSamples outside block size")
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}
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d.FieldArrayFn("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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riceBits := int(d.FieldUFn("residual_coding_method", func() (uint64, decode.DisplayFormat, string) {
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switch d.U2() {
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case 0b00:
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riceEscape = 0b1111
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return 4, decode.NumberDecimal, "rice"
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case 0b01:
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riceEscape = 0b11111
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return 5, decode.NumberDecimal, "rice2"
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default:
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d.Invalid("unknown residual_coding_method")
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return 0, 0, ""
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}
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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.FieldArrayFn("partitions", func(d *decode.D) {
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for i := 0; i < ricePartitions; i++ {
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d.FieldStructFn("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:
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// if the partition order is zero, n = frame's blocksize - predictor order
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// else if this is not the first partition of the subframe, n = (frame's blocksize / (2^partition order))
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// else n = (frame's blocksize / (2^partition order)) - predictor order
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var count int
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if partitionOrder == 0 {
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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.Invalid("decodeResiduals outside block size")
|
|
}
|
|
|
|
if riceParameter == riceEscape {
|
|
escapeSampleSize := int(d.FieldU5("escape_sample_size"))
|
|
d.FieldBitBufLen("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.FieldBitBufRange("samples", samplesStart, samplesStop-samplesStart)
|
|
}
|
|
})
|
|
}
|
|
})
|
|
}
|
|
|
|
// 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 subframeType {
|
|
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.FieldBitBufRange("samples", d.Pos(), int64(blockSize*subframeSampleSize))
|
|
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.FieldUFn("precision", func() (uint64, decode.DisplayFormat, string) {
|
|
return d.U4() + 1, decode.NumberDecimal, ""
|
|
}))
|
|
// <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.Invalid(fmt.Sprintf("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.FieldArrayFn("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.FieldValidateUFn("byte_align", 0, func() uint64 { return d.U(d.ByteAlignBits()) })
|
|
// <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 := &crc.CRC{Bits: 16, Table: crc.ANSI16Table}
|
|
decode.MustCopy(d, footerCRC, d.BitBufRange(frameStart, d.Pos()-frameStart))
|
|
d.FieldChecksumLen("footer_crc", 16, footerCRC.Sum(nil), decode.BigEndian)
|
|
|
|
streamSamples := len(channelSamples[0])
|
|
for j := 0; j < len(channelSamples); j++ {
|
|
if streamSamples > len(channelSamples[j]) {
|
|
d.Invalid(fmt.Sprintf("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: int(channels),
|
|
BitsPerSample: outSampleSize,
|
|
}
|
|
}
|