Add Ogg Opus metadata support (#69)
Refactor into a ogg demuxer that returns slice of packets and then look for first vorbis comment or opus tags packet. Fixes #64
This commit is contained in:
Mattias Wadman
GitHub
parent
d52dcb253c
commit
77907a30b7
271
ogg.go
271
ogg.go
@ -6,156 +6,163 @@ package tag
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import (
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"bytes"
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"encoding/binary"
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"errors"
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"fmt"
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"io"
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)
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const (
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idType int = 1
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commentType int = 3
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var (
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vorbisCommentPrefix = []byte("\x03vorbis")
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opusTagsPrefix = []byte("OpusTags")
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)
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var oggCRC32Poly04c11db7 = oggCRCTable(0x04c11db7)
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type crc32Table [256]uint32
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func oggCRCTable(poly uint32) *crc32Table {
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var t crc32Table
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for i := 0; i < 256; i++ {
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crc := uint32(i) << 24
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for j := 0; j < 8; j++ {
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if crc&0x80000000 != 0 {
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crc = (crc << 1) ^ poly
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} else {
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crc <<= 1
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}
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}
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t[i] = crc
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}
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return &t
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}
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func oggCRCUpdate(crc uint32, tab *crc32Table, p []byte) uint32 {
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for _, v := range p {
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crc = (crc << 8) ^ tab[byte(crc>>24)^v]
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}
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return crc
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}
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type oggPageHeader struct {
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Magic [4]byte // "OggS"
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Version uint8
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Flags uint8
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GranulePosition uint64
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SerialNumber uint32
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SequenceNumber uint32
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CRC uint32
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Segments uint8
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}
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type oggDemuxer struct {
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packetBufs map[uint32]*bytes.Buffer
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}
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// Read ogg packets, can return empty slice of packets and nil err
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// if more data is needed
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func (o *oggDemuxer) Read(r io.Reader) ([][]byte, error) {
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headerBuf := &bytes.Buffer{}
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var oh oggPageHeader
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if err := binary.Read(io.TeeReader(r, headerBuf), binary.LittleEndian, &oh); err != nil {
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return nil, err
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}
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if bytes.Compare(oh.Magic[:], []byte("OggS")) != 0 {
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// TODO: seek for syncword?
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return nil, errors.New("expected 'OggS'")
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}
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segmentTable := make([]byte, oh.Segments)
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if _, err := io.ReadFull(r, segmentTable); err != nil {
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return nil, err
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}
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var segmentsSize int64
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for _, s := range segmentTable {
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segmentsSize += int64(s)
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}
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segmentsData := make([]byte, segmentsSize)
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if _, err := io.ReadFull(r, segmentsData); err != nil {
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return nil, err
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}
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headerBytes := headerBuf.Bytes()
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// reset CRC to zero in header before checksum
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headerBytes[22] = 0
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headerBytes[23] = 0
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headerBytes[24] = 0
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headerBytes[25] = 0
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crc := oggCRCUpdate(0, oggCRC32Poly04c11db7, headerBytes)
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crc = oggCRCUpdate(crc, oggCRC32Poly04c11db7, segmentTable)
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crc = oggCRCUpdate(crc, oggCRC32Poly04c11db7, segmentsData)
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if crc != oh.CRC {
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return nil, fmt.Errorf("expected crc %x != %x", oh.CRC, crc)
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}
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if o.packetBufs == nil {
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o.packetBufs = map[uint32]*bytes.Buffer{}
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}
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var packetBuf *bytes.Buffer
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continued := oh.Flags&0x1 != 0
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if continued {
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if b, ok := o.packetBufs[oh.SerialNumber]; ok {
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packetBuf = b
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} else {
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return nil, fmt.Errorf("could not find continued packet %d", oh.SerialNumber)
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}
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} else {
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packetBuf = &bytes.Buffer{}
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}
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var packets [][]byte
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var p int
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for _, s := range segmentTable {
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packetBuf.Write(segmentsData[p : p+int(s)])
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if s < 255 {
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packets = append(packets, packetBuf.Bytes())
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packetBuf = &bytes.Buffer{}
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}
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p += int(s)
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}
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o.packetBufs[oh.SerialNumber] = packetBuf
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return packets, nil
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}
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// ReadOGGTags reads OGG metadata from the io.ReadSeeker, returning the resulting
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// metadata in a Metadata implementation, or non-nil error if there was a problem.
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// See http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html
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// and http://www.xiph.org/ogg/doc/framing.html for details.
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func ReadOGGTags(r io.ReadSeeker) (Metadata, error) {
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oggs, err := readString(r, 4)
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if err != nil {
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return nil, err
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}
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if oggs != "OggS" {
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return nil, errors.New("expected 'OggS'")
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}
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// Skip 22 bytes of Page header to read page_segments length byte at position 26
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// See http://www.xiph.org/ogg/doc/framing.html
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_, err = r.Seek(22, io.SeekCurrent)
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if err != nil {
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return nil, err
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}
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nS, err := readInt(r, 1)
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if err != nil {
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return nil, err
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}
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// Seek and discard the segments
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_, err = r.Seek(int64(nS), io.SeekCurrent)
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if err != nil {
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return nil, err
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}
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// First packet type is identification, type 1
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t, err := readInt(r, 1)
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if err != nil {
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return nil, err
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}
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if t != idType {
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return nil, errors.New("expected 'vorbis' identification type 1")
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}
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// Seek and discard 29 bytes from common and identification header
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// See http://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-610004.2
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_, err = r.Seek(29, io.SeekCurrent)
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if err != nil {
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return nil, err
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}
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// Read comment header packet. May include setup header packet, if it is on the
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// same page. First audio packet is guaranteed to be on the separate page.
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// See https://www.xiph.org/vorbis/doc/Vorbis_I_spec.html#x1-132000A.2
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ch, err := readPackets(r)
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if err != nil {
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return nil, err
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}
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chr := bytes.NewReader(ch)
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// First packet type is comment, type 3
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t, err = readInt(chr, 1)
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if err != nil {
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return nil, err
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}
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if t != commentType {
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return nil, errors.New("expected 'vorbis' comment type 3")
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}
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// Seek and discard 6 bytes from common header
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_, err = chr.Seek(6, io.SeekCurrent)
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if err != nil {
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return nil, err
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}
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m := &metadataOGG{
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newMetadataVorbis(),
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}
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err = m.readVorbisComment(chr)
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return m, err
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}
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// readPackets reads vorbis header packets from contiguous ogg pages in ReadSeeker.
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// The pages are considered contiguous, if the first lacing value in second
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// page's segment table continues rather than begins a packet. This is indicated
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// by setting header_type_flag 0x1 (continued packet).
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// See https://www.xiph.org/ogg/doc/framing.html on packets spanning pages.
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func readPackets(r io.ReadSeeker) ([]byte, error) {
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buf := &bytes.Buffer{}
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firstPage := true
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// For Opus see https://tools.ietf.org/html/rfc7845
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func ReadOGGTags(r io.Reader) (Metadata, error) {
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od := &oggDemuxer{}
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for {
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// Read capture pattern
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oggs, err := readString(r, 4)
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bs, err := od.Read(r)
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if err != nil {
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return nil, err
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}
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if oggs != "OggS" {
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return nil, errors.New("expected 'OggS'")
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}
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// Read page header
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head, err := readBytes(r, 22)
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if err != nil {
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return nil, err
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}
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headerTypeFlag := head[1]
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continuation := headerTypeFlag&0x1 > 0
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if !(firstPage || continuation) {
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// Rewind to the beginning of the page
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_, err = r.Seek(-26, io.SeekCurrent)
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if err != nil {
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return nil, err
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for _, b := range bs {
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switch {
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case bytes.HasPrefix(b, vorbisCommentPrefix):
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m := &metadataOGG{
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newMetadataVorbis(),
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}
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err = m.readVorbisComment(bytes.NewReader(b[len(vorbisCommentPrefix):]))
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return m, err
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case bytes.HasPrefix(b, opusTagsPrefix):
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m := &metadataOGG{
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newMetadataVorbis(),
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}
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err = m.readVorbisComment(bytes.NewReader(b[len(opusTagsPrefix):]))
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return m, err
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}
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break
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}
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firstPage = false
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// Read the number of segments
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nS, err := readUint(r, 1)
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if err != nil {
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return nil, err
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}
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// Read segment table
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segments, err := readBytes(r, nS)
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if err != nil {
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return nil, err
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}
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// Calculate remaining page size
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pageSize := 0
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for i := uint(0); i < nS; i++ {
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pageSize += int(segments[i])
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}
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_, err = io.CopyN(buf, r, int64(pageSize))
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if err != nil {
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return nil, err
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}
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}
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return buf.Bytes(), nil
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}
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type metadataOGG struct {
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