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126 lines
3.6 KiB
Go
126 lines
3.6 KiB
Go
package vorbis
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// https://xiph.org/vorbis/doc/Vorbis_I_spec.html
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// TODO: setup? more audio?
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// TODO: end padding? byte align?
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import (
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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/pkg/decode"
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"github.com/wader/fq/pkg/scalar"
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)
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var vorbisComment decode.Group
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func init() {
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registry.MustRegister(decode.Format{
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Name: format.VORBIS_PACKET,
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Description: "Vorbis packet",
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DecodeFn: vorbisDecode,
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Dependencies: []decode.Dependency{
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{Names: []string{format.VORBIS_COMMENT}, Group: &vorbisComment},
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},
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})
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}
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const (
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packetTypeAudio = 0
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packetTypeIdentification = 1
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packetTypeComment = 3
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packetTypeSetup = 5
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)
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var packetTypeNames = map[uint]string{
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packetTypeAudio: "Audio",
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packetTypeIdentification: "Identification",
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packetTypeComment: "Comment",
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packetTypeSetup: "Setup",
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}
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func vorbisDecode(d *decode.D, in interface{}) interface{} {
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d.Endian = decode.LittleEndian
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packetType := d.FieldUScalarFn("packet_type", func(d *decode.D) scalar.S {
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packetTypeName := "unknown"
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t := d.U8()
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// 4.2.1. Common header decode
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// "these types are all odd as a packet with a leading single bit of ’0’ is an audio packet"
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if t&1 == 0 {
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t = packetTypeAudio
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}
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if n, ok := packetTypeNames[uint(t)]; ok {
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packetTypeName = n
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}
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return scalar.S{Actual: t, Sym: packetTypeName}
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})
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switch packetType {
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case packetTypeIdentification, packetTypeSetup, packetTypeComment:
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d.FieldUTF8("magic", 6, d.AssertStr("vorbis"))
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case packetTypeAudio:
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default:
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d.Fatalf("unknown packet type %d", packetType)
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}
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switch packetType {
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case packetTypeAudio:
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case packetTypeIdentification:
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// 1 1) [vorbis_version] = read 32 bits as unsigned integer
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// 2 2) [audio_channels] = read 8 bit integer as unsigned
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// 3 3) [audio_sample_rate] = read 32 bits as unsigned integer
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// 4 4) [bitrate_maximum] = read 32 bits as signed integer
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// 5 5) [bitrate_nominal] = read 32 bits as signed integer
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// 6 6) [bitrate_minimum] = read 32 bits as signed integer
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// 7 7) [blocksize_0] = 2 exponent (read 4 bits as unsigned integer)
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// 8 8) [blocksize_1] = 2 exponent (read 4 bits as unsigned integer)
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// 9 9) [framing_flag] = read one bit
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d.FieldU32("vorbis_version", d.ValidateU(0))
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d.FieldU8("audio_channels")
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d.FieldU32("audio_sample_rate")
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d.FieldU32("bitrate_maximum")
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d.FieldU32("bitrate_nominal")
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d.FieldU32("bitrate_minimum")
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// TODO: code/comment about 2.1.4. coding bits into byte sequences
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d.FieldUFn("blocksize_1", func(d *decode.D) uint64 { return 1 << d.U4() })
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d.FieldUFn("blocksize_0", func(d *decode.D) uint64 { return 1 << d.U4() })
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// TODO: warning if blocksize0 > blocksize1
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// TODO: warning if not 64-8192
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d.FieldRawLen("padding0", 7, d.BitBufIsZero())
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d.FieldU1("framing_flag", d.ValidateU(1))
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case packetTypeSetup:
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d.FieldUFn("vorbis_codebook_count", func(d *decode.D) uint64 { return d.U8() + 1 })
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d.FieldU24("codecooke_sync", d.ValidateU(0x564342), scalar.Hex)
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d.FieldU16("codebook_dimensions")
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d.FieldU24("codebook_entries")
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// d.SeekRel(7)
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// ordered := d.FieldBool("ordered")
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// if ordered {
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// } else {
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// d.SeekRel(-2)
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// sparse := d.FieldBool("sparse")
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// d.SeekRel(1)
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// if sparse {
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// } else {
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// d.SeekRel(-7)
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// d.FieldU5("length")
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// }
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// }
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case packetTypeComment:
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d.FieldFormat("comment", vorbisComment, nil)
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// note this uses vorbis bitpacking convention, bits are added LSB first per byte
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d.FieldRawLen("padding0", 7, d.BitBufIsZero())
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d.FieldU1("frame_bit", d.ValidateU(1))
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}
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return nil
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}
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