r4/radio-stream-recorder
1
0
Fork 0
Code Issues Pull Requests Projects Releases 1 Wiki Activity

Initial commit

Browse Source
This commit is contained in:
r4
2021-06-03 19:07:27 +02:00
parent 308f0429b3
commit 2be4bf1a5e
8 changed files with 662 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

144
vorbis/metadata.go Normal file
View File

@@ -0,0 +1,144 @@
// Minimal 'Vorbis comment' metadata reader oriented around
// https://xiph.org/vorbis/doc/Vorbis_I_spec.html and its reference
// implementation written in C.
package vorbis
import (
"encoding/binary"
"errors"
"io"
"strings"
)
var (
ErrVorbisHeaderType = errors.New("vorbis: header not Vorbis")
ErrVorbisInvalidCommentFormat = errors.New("vorbis: invalid Vorbis comment")
)
type VorbisCommentField struct {
// According to the spec, the key capitalization doesn't matter, which is
// why we're using uppercase letters only in this implementation
// (see `VorbisCommentDecode()`).
Key string
// The value has some restrictions for what characters it can contain, but
// we're ignoring them for now.
Val string
}
// Track metadata represented by a Vorbis comment. The fields should be
// self-explanatory.
type VorbisComment struct {
Vendor string
Fields []VorbisCommentField
}
// Attempts to decode a Vorbis comment, leaving the reader `r` right past the
// data it decoded.
func VorbisCommentDecode(r io.Reader) (VorbisComment, error) {
var ret VorbisComment
// In Vorbis comment, strings are always preceded by a 32-bit length
// specifier.
getNextString := func() ([]byte, error) {
var sz uint32
err := binary.Read(r, binary.LittleEndian, &sz)
if err != nil {
return nil, err
}
content := make([]byte, sz)
_, err = r.Read(content)
if err != nil {
return nil, err
}
return content, nil
}
content, err := getNextString()
if err != nil {
return ret, err
}
ret.Vendor = string(content)
var numCommentFields uint32
err = binary.Read(r, binary.LittleEndian, &numCommentFields)
if err != nil {
return ret, err
}
for i := 0; i < int(numCommentFields); i++ {
content, err := getNextString()
if err != nil {
return ret, err
}
splits := strings.Split(string(content), "=")
if len(splits) != 2 {
return ret, ErrVorbisInvalidCommentFormat
}
var newField VorbisCommentField
newField.Key = strings.ToUpper(splits[0])
newField.Val = splits[1]
ret.Fields = append(ret.Fields, newField)
}
return ret, nil
}
// Field names are searched case insensitively, as specified in the spec.
// `found` is set to false if the field doesn't exist.
func (c *VorbisComment) FieldByName(name string) (val string, found bool) {
// All field names are stored as upper case strings in this implementation.
// That is why we only need to transform the search query string to
// uppercase.
upperName := strings.ToUpper(name)
// Linearly search through field names.
for _, v := range c.Fields {
if v.Key == upperName {
return v.Val, true
}
}
return "", false
}
var (
PackTypeInfo = uint8(0x1)
PackTypeComment = uint8(0x3) // Comment is the only one we really care about here.
PackTypeBooks = uint8(0x5)
)
type VorbisHeader struct {
PackType uint8
Comment *VorbisComment
}
func VorbisHeaderDecode(r io.Reader) (VorbisHeader, error) {
var ret VorbisHeader
err := binary.Read(r, binary.LittleEndian, &ret.PackType)
if err != nil {
return ret, err
}
switch ret.PackType {
case PackTypeComment:
buf := make([]byte, 6)
_, err = r.Read(buf)
if err != nil {
return ret, err
}
if string(buf) != "vorbis" {
return ret, ErrVorbisHeaderType
}
comment, err := VorbisCommentDecode(r)
if err != nil {
return ret, err
}
ret.Comment = &comment
}
return ret, nil
}

202
vorbis/ogg.go Normal file
View File

@@ -0,0 +1,202 @@
// Minimal Ogg decoder according to rfc3533
// (https://www.xiph.org/ogg/doc/rfc3533.txt). Whenever 'the spec' is mentioned,
// it is referring to rfc3533.
package vorbis
import (
"bytes"
"encoding/binary"
"errors"
"io"
)
var (
ErrOggInvalidMagicNumber = errors.New("ogg: invalid magic number")
ErrOggInvalidChecksum = errors.New("ogg: invalid checksum")
)
const (
headerSize = 27
// Uncombined segments are meant here (see Page.Segments or the spec for
// more details about segments).
maxSegments = 255
maxSegmentSize = 255
maxPageSize = headerSize + maxSegments + maxSegments*maxSegmentSize
)
// Using polynomial 0x04c11db7 (see the spec).
var crcLookup = [256]uint32{
0x00000000, 0x04c11db7, 0x09823b6e, 0x0d4326d9,
0x130476dc, 0x17c56b6b, 0x1a864db2, 0x1e475005,
0x2608edb8, 0x22c9f00f, 0x2f8ad6d6, 0x2b4bcb61,
0x350c9b64, 0x31cd86d3, 0x3c8ea00a, 0x384fbdbd,
0x4c11db70, 0x48d0c6c7, 0x4593e01e, 0x4152fda9,
0x5f15adac, 0x5bd4b01b, 0x569796c2, 0x52568b75,
0x6a1936c8, 0x6ed82b7f, 0x639b0da6, 0x675a1011,
0x791d4014, 0x7ddc5da3, 0x709f7b7a, 0x745e66cd,
0x9823b6e0, 0x9ce2ab57, 0x91a18d8e, 0x95609039,
0x8b27c03c, 0x8fe6dd8b, 0x82a5fb52, 0x8664e6e5,
0xbe2b5b58, 0xbaea46ef, 0xb7a96036, 0xb3687d81,
0xad2f2d84, 0xa9ee3033, 0xa4ad16ea, 0xa06c0b5d,
0xd4326d90, 0xd0f37027, 0xddb056fe, 0xd9714b49,
0xc7361b4c, 0xc3f706fb, 0xceb42022, 0xca753d95,
0xf23a8028, 0xf6fb9d9f, 0xfbb8bb46, 0xff79a6f1,
0xe13ef6f4, 0xe5ffeb43, 0xe8bccd9a, 0xec7dd02d,
0x34867077, 0x30476dc0, 0x3d044b19, 0x39c556ae,
0x278206ab, 0x23431b1c, 0x2e003dc5, 0x2ac12072,
0x128e9dcf, 0x164f8078, 0x1b0ca6a1, 0x1fcdbb16,
0x018aeb13, 0x054bf6a4, 0x0808d07d, 0x0cc9cdca,
0x7897ab07, 0x7c56b6b0, 0x71159069, 0x75d48dde,
0x6b93dddb, 0x6f52c06c, 0x6211e6b5, 0x66d0fb02,
0x5e9f46bf, 0x5a5e5b08, 0x571d7dd1, 0x53dc6066,
0x4d9b3063, 0x495a2dd4, 0x44190b0d, 0x40d816ba,
0xaca5c697, 0xa864db20, 0xa527fdf9, 0xa1e6e04e,
0xbfa1b04b, 0xbb60adfc, 0xb6238b25, 0xb2e29692,
0x8aad2b2f, 0x8e6c3698, 0x832f1041, 0x87ee0df6,
0x99a95df3, 0x9d684044, 0x902b669d, 0x94ea7b2a,
0xe0b41de7, 0xe4750050, 0xe9362689, 0xedf73b3e,
0xf3b06b3b, 0xf771768c, 0xfa325055, 0xfef34de2,
0xc6bcf05f, 0xc27dede8, 0xcf3ecb31, 0xcbffd686,
0xd5b88683, 0xd1799b34, 0xdc3abded, 0xd8fba05a,
0x690ce0ee, 0x6dcdfd59, 0x608edb80, 0x644fc637,
0x7a089632, 0x7ec98b85, 0x738aad5c, 0x774bb0eb,
0x4f040d56, 0x4bc510e1, 0x46863638, 0x42472b8f,
0x5c007b8a, 0x58c1663d, 0x558240e4, 0x51435d53,
0x251d3b9e, 0x21dc2629, 0x2c9f00f0, 0x285e1d47,
0x36194d42, 0x32d850f5, 0x3f9b762c, 0x3b5a6b9b,
0x0315d626, 0x07d4cb91, 0x0a97ed48, 0x0e56f0ff,
0x1011a0fa, 0x14d0bd4d, 0x19939b94, 0x1d528623,
0xf12f560e, 0xf5ee4bb9, 0xf8ad6d60, 0xfc6c70d7,
0xe22b20d2, 0xe6ea3d65, 0xeba91bbc, 0xef68060b,
0xd727bbb6, 0xd3e6a601, 0xdea580d8, 0xda649d6f,
0xc423cd6a, 0xc0e2d0dd, 0xcda1f604, 0xc960ebb3,
0xbd3e8d7e, 0xb9ff90c9, 0xb4bcb610, 0xb07daba7,
0xae3afba2, 0xaafbe615, 0xa7b8c0cc, 0xa379dd7b,
0x9b3660c6, 0x9ff77d71, 0x92b45ba8, 0x9675461f,
0x8832161a, 0x8cf30bad, 0x81b02d74, 0x857130c3,
0x5d8a9099, 0x594b8d2e, 0x5408abf7, 0x50c9b640,
0x4e8ee645, 0x4a4ffbf2, 0x470cdd2b, 0x43cdc09c,
0x7b827d21, 0x7f436096, 0x7200464f, 0x76c15bf8,
0x68860bfd, 0x6c47164a, 0x61043093, 0x65c52d24,
0x119b4be9, 0x155a565e, 0x18197087, 0x1cd86d30,
0x029f3d35, 0x065e2082, 0x0b1d065b, 0x0fdc1bec,
0x3793a651, 0x3352bbe6, 0x3e119d3f, 0x3ad08088,
0x2497d08d, 0x2056cd3a, 0x2d15ebe3, 0x29d4f654,
0xc5a92679, 0xc1683bce, 0xcc2b1d17, 0xc8ea00a0,
0xd6ad50a5, 0xd26c4d12, 0xdf2f6bcb, 0xdbee767c,
0xe3a1cbc1, 0xe760d676, 0xea23f0af, 0xeee2ed18,
0xf0a5bd1d, 0xf464a0aa, 0xf9278673, 0xfde69bc4,
0x89b8fd09, 0x8d79e0be, 0x803ac667, 0x84fbdbd0,
0x9abc8bd5, 0x9e7d9662, 0x933eb0bb, 0x97ffad0c,
0xafb010b1, 0xab710d06, 0xa6322bdf, 0xa2f33668,
0xbcb4666d, 0xb8757bda, 0xb5365d03, 0xb1f740b4,
}
type crc32Writer struct {
sum uint32
}
func (w *crc32Writer) Write(p []byte) (n int, err error) {
for _, v := range p {
w.sum = (w.sum << 8) ^ crcLookup[uint8(w.sum>>24)^v]
}
return len(p), nil
}
var (
FHeaderTypeContinuation = uint8(0x1)
FHeaderTypeBOS = uint8(0x2) // Beginning of stream
FHeaderTypeEOS = uint8(0x4) // End of stream
)
// See the spec for more info on the individual fields.
type OggPageHeader struct {
MagicNumber [4]uint8
Version uint8
HeaderType uint8
GranulePosition uint64
BitstreamSerialNum uint32
PageSequenceNum uint32
Checksum uint32
NumSegments uint8 // Number of uncombined segments (see Page.Segments or the spec for more details).
}
type OggPage struct {
Header OggPageHeader
// These are the combined segments. The spec says that when a segment is
// said to have a length of 255, it is to be combined with the next segment,
// which is already done here.
Segments [][]byte
}
// Decodes the given raw Ogg page according to rfc3533
// (https://www.xiph.org/ogg/doc/rfc3533.txt).
// The given reader `r` must be set to start at the beginning of the page, i.e.
// at the magic number "OggS".
// Leaves the reader position at the beginning of the next page (or EOF if
// the decoded page was the last page).
func OggDecode(r io.Reader) (OggPage, error) {
var ret OggPage
checksum := &crc32Writer{}
// Read header into struct and into byte buffer.
var rawHeaderBuf bytes.Buffer
hdrR := io.TeeReader(r, &rawHeaderBuf)
err := binary.Read(hdrR, binary.LittleEndian, &ret.Header)
if err != nil {
return ret, err
}
// Validate magic number.
if string(ret.Header.MagicNumber[:]) != "OggS" {
return ret, ErrOggInvalidMagicNumber
}
// Get raw header bytes, then set the header checksum field to 0 before
// calculating the checksum (see the spec).
rawHeader, err := io.ReadAll(&rawHeaderBuf)
if err != nil {
return ret, err
}
for i := 22; i <= 25; i++ {
rawHeader[i] = 0
}
// Add raw header to checksum.
checksum.Write(rawHeader) // Can't give an error (see implementation).
// From now on, write everything that is read into the checksum.
teeR := io.TeeReader(r, checksum)
// Read the sizes of all segments in the page.
segsizes := make([]byte, ret.Header.NumSegments)
teeR.Read(segsizes)
// Whether to append to the last segment. According to the spec, whenever
// a segment length is specified as being 255, that means the next segment
// should be appended to it.
var app bool
// Parse the segments, respecting combining segments (see the spec).
for _, v := range segsizes {
sz := int(v)
content := make([]byte, sz)
teeR.Read(content)
if app {
lastSeg := &ret.Segments[len(ret.Segments)-1]
*lastSeg = append(*lastSeg, content...)
} else {
ret.Segments = append(ret.Segments, content)
}
app = sz == 255
}
// Verify the checksum.
if checksum.sum != ret.Header.Checksum {
return ret, ErrOggInvalidChecksum
}
return ret, nil
}

96
vorbis/vorbis.go Normal file
View File

@@ -0,0 +1,96 @@
package vorbis
import (
"bytes"
"errors"
"io"
)
var (
ErrNoHeaderSegment = errors.New("no header segment")
ErrNoMetadata = errors.New("no metadata found")
ErrCallReadRestAfterReadMetadata = errors.New("please call vorbis.Decoder.ReadRest() after having called vorbis.Decoder.ReadMetadata()")
ErrReadMetadataCalledTwice = errors.New("cannot call vorbis.Decoder.ReadMetadata() twice on the same file")
)
type Decoder struct {
r io.Reader
hasMetadata bool
}
func NewDecoder(r io.Reader) *Decoder {
return &Decoder{
r: r,
}
}
func (d *Decoder) readPage() (page OggPage, hdr VorbisHeader, err error) {
// Decode page.
page, err = OggDecode(d.r)
if err != nil {
return page, hdr, err
}
// We need to be able to access `page.Segments[0]`.
if len(page.Segments) == 0 {
return page, hdr, ErrNoHeaderSegment
}
// Decode Vorbis header, stored in `page.Segments[0]`.
hdr, err = VorbisHeaderDecode(bytes.NewBuffer(page.Segments[0]))
if err != nil {
return page, hdr, err
}
return page, hdr, nil
}
// Reads the Ogg/Vorbis file until it finds its metadata. Leaves the reader
// right after the end of the metadata. `crc32Sum` gives the crc32 checksum
// of the page containing the metadata. It is equivalent to the page checksum
// used in the Ogg container. Since the page contains more than just metadata,
// the checksum can usually be used as a unique identifier.
func (d *Decoder) ReadMetadata() (metadata *VorbisComment, crc32Sum uint32, err error) {
if d.hasMetadata {
return nil, 0, ErrReadMetadataCalledTwice
}
for {
page, hdr, err := d.readPage()
if err != nil {
return nil, 0, err
}
if (page.Header.HeaderType & FHeaderTypeEOS) > 0 {
// End of stream
return nil, 0, ErrNoMetadata
}
if hdr.PackType == PackTypeComment {
d.hasMetadata = true
return hdr.Comment, page.Header.Checksum, nil
}
}
}
// Must to be called after `ReadMetadata()`. Reads the rest of the Ogg/Vorbis
// file, leaving the reader right after the end of the Ogg/Vorbis file.
func (d *Decoder) ReadRest() error {
if !d.hasMetadata {
return ErrCallReadRestAfterReadMetadata
}
for {
page, _, err := d.readPage()
if err != nil {
return err
}
if (page.Header.HeaderType & FHeaderTypeEOS) > 0 {
// End of stream
break
}
}
return nil
}