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fq/format/vorbis/vorbis_packet.go

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package vorbis
// https://xiph.org/vorbis/doc/Vorbis_I_spec.html
// TODO: setup? more audio?
// TODO: end padding? byte align?
import (
"fmt"
"github.com/wader/fq/format"
"github.com/wader/fq/format/registry"
"github.com/wader/fq/pkg/decode"
)
var vorbisComment []*decode.Format
func init() {
registry.MustRegister(&decode.Format{
Name: format.VORBIS_PACKET,
Description: "Vorbis packet",
DecodeFn: vorbisDecode,
Dependencies: []decode.Dependency{
{Names: []string{format.VORBIS_COMMENT}, Formats: &vorbisComment},
},
})
}
const (
packetTypeAudio = 0
packetTypeIdentification = 1
packetTypeComment = 3
packetTypeSetup = 5
)
var packetTypeNames = map[uint]string{
packetTypeAudio: "Audio",
packetTypeIdentification: "Identification",
packetTypeComment: "Comment",
packetTypeSetup: "Setup",
}
func vorbisDecode(d *decode.D, in interface{}) interface{} {
packetType := d.FieldUFn("packet_type", func() (uint64, decode.DisplayFormat, string) {
packetTypeName := "unknown"
t := d.U8()
// 4.2.1. Common header decode
// "these types are all odd as a packet with a leading single bit of 0 is an audio packet"
if t&1 == 0 {
t = packetTypeAudio
}
if n, ok := packetTypeNames[uint(t)]; ok {
packetTypeName = n
}
return t, decode.NumberDecimal, packetTypeName
})
switch packetType {
case packetTypeIdentification, packetTypeSetup, packetTypeComment:
d.FieldValidateUTF8("magic", "vorbis")
case packetTypeAudio:
default:
d.Invalid(fmt.Sprintf("unknown packet type %d", packetType))
}
switch packetType {
case packetTypeAudio:
case packetTypeIdentification:
// 1 1) [vorbis_version] = read 32 bits as unsigned integer
// 2 2) [audio_channels] = read 8 bit integer as unsigned
// 3 3) [audio_sample_rate] = read 32 bits as unsigned integer
// 4 4) [bitrate_maximum] = read 32 bits as signed integer
// 5 5) [bitrate_nominal] = read 32 bits as signed integer
// 6 6) [bitrate_minimum] = read 32 bits as signed integer
// 7 7) [blocksize_0] = 2 exponent (read 4 bits as unsigned integer)
// 8 8) [blocksize_1] = 2 exponent (read 4 bits as unsigned integer)
// 9 9) [framing_flag] = read one bit
d.FieldValidateUFn("vorbis_version", 0, d.U32LE)
d.FieldU8("audio_channels")
d.FieldU32LE("audio_sample_rate")
d.FieldU32LE("bitrate_maximum")
d.FieldU32LE("bitrate_nominal")
d.FieldU32LE("bitrate_minimum")
// TODO: code/comment about 2.1.4. coding bits into byte sequences
d.FieldUFn("blocksize_1", func() (uint64, decode.DisplayFormat, string) {
return 1 << d.U4(), decode.NumberDecimal, ""
})
d.FieldUFn("blocksize_0", func() (uint64, decode.DisplayFormat, string) {
return 1 << d.U4(), decode.NumberDecimal, ""
})
// TODO: warning if blocksize0 > blocksize1
// TODO: warning if not 64-8192
d.FieldValidateZeroPadding("padding0", 7)
d.FieldValidateUFn("framing_flag", 1, d.U1)
case packetTypeSetup:
d.FieldUFn("vorbis_codebook_count", func() (uint64, decode.DisplayFormat, string) {
return d.U8() + 1, decode.NumberDecimal, ""
})
d.FieldValidateUFn("codecooke_sync", 0x564342, d.U24LE)
d.FieldU16LE("codebook_dimensions")
d.FieldU24LE("codebook_entries")
// d.SeekRel(7)
// ordered := d.FieldBool("ordered")
// if ordered {
// } else {
// d.SeekRel(-2)
// sparse := d.FieldBool("sparse")
// d.SeekRel(1)
// if sparse {
// } else {
// d.SeekRel(-7)
// d.FieldU5("length")
// }
// }
case packetTypeComment:
d.FieldFormat("comment", vorbisComment, nil)
// note this uses vorbis bitpacking convention, bits are added LSB first per byte
d.FieldValidateZeroPadding("padding0", 7)
d.FieldValidateUFn("frame_bit", 1, d.U1)
}
return nil
}