// ReadHeaders allows to init info and comment from a private codec data payload
// when no Ogg stream is available. Info and comment must be initialised beforehand.
func ReadHeaders(codecPriv []byte, info *vorbis.Info, comment *vorbis.Comment) error {
if len(codecPriv) == 0 {
return errors.New("vorbis decoder: no codec private data")
}
headerSizes := make([]int, 3)
headers := make([][]byte, 3)
p := codecPriv
if p[0] == 0x00 && p[1] == 0x30 {
for i := 0; i < 3; i++ {
headerSizes[i] = int(uint16(p[0])<<8 | uint16(p[1]))
headers[i] = p
p = p[headerSizes[i]:]
}
} else if p[0] == 0x02 {
offset := 1
p = p[1:]
for i := 0; i < 2; i++ {
headerSizes[i] = 0
for (p[0] == 0xFF) && offset < len(codecPriv) {
headerSizes[i] += 0xFF
offset++
p = p[1:]
}
if offset >= len(codecPriv)-1 {
return errors.New("vorbis decoder: header sizes damaged")
}
headerSizes[i] += int(p[0])
offset++
p = p[1:]
}
headerSizes[2] = len(codecPriv) - headerSizes[0] - headerSizes[1] - offset
headers[0] = codecPriv[offset:]
headers[1] = codecPriv[offset+headerSizes[0]:]
headers[2] = codecPriv[offset+headerSizes[0]+headerSizes[1]:]
} else {
return fmt.Errorf("vorbis decoder: initial header len is wrong: %d", p[0])
}
for i := 0; i < 3; i++ {
packet := vorbis.OggPacket{
BOS: b(i == 0),
Bytes: headerSizes[i],
Packet: headers[i],
}
if ret := vorbis.SynthesisHeaderin(info, comment, &packet); ret < 0 {
return fmt.Errorf("vorbis decoder: %d. header damaged", i+1)
}
}
return nil
}
func (d *Decoder) readStreamHeaders(r io.Reader) error {
d.readChunk(r)
// Read the first page
if ret := vorbis.OggSyncPageout(&d.syncState, &d.page); ret != 1 {
return errors.New("vorbis: not a valid Ogg bitstream")
}
// Init the logical bitstream with serial number stored in the page
vorbis.OggStreamInit(&d.streamState, vorbis.OggPageSerialno(&d.page))
vorbis.InfoInit(&d.info)
vorbis.CommentInit(&d.comment)
// Add a complete page to the bitstream
if ret := vorbis.OggStreamPagein(&d.streamState, &d.page); ret < 0 {
return errors.New("vorbis: the supplied page does not belong this Vorbis stream")
}
// Get the first packet
if ret := vorbis.OggStreamPacketout(&d.streamState, &d.packet); ret != 1 {
return errors.New("vorbis: unable to fetch initial Vorbis packet from the first page")
}
// Finally decode the header packet
if ret := vorbis.SynthesisHeaderin(&d.info, &d.comment, &d.packet); ret < 0 {
return fmt.Errorf("vorbis: unable to decode the initial Vorbis header: %d", ret)
}
var headersRead int
forPage:
for headersRead < 2 {
if res := vorbis.OggSyncPageout(&d.syncState, &d.page); res < 0 {
// bytes have been skipped, try to sync again
continue forPage
} else if res == 0 {
// go get more data
if _, err := d.readChunk(r); err != nil {
return errors.New("vorbis: got EOF while reading Vorbis headers")
}
continue forPage
}
// page is synced at this point
vorbis.OggStreamPagein(&d.streamState, &d.page)
for headersRead < 2 {
if ret := vorbis.OggStreamPacketout(&d.streamState, &d.packet); ret < 0 {
return errors.New("vorbis: data is missing near the secondary Vorbis header")
} else if ret == 0 {
// no packets left on the page, go get a new one
continue forPage
}
if ret := vorbis.SynthesisHeaderin(&d.info, &d.comment, &d.packet); ret < 0 {
return errors.New("vorbis: unable to read the secondary Vorbis header")
}
headersRead++
}
}
d.info.Deref()
d.comment.Deref()
d.comment.UserComments = make([][]byte, d.comment.Comments)
d.comment.Deref()
return nil
}