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Implemented OggReadFile() func to get raw data from an OGG file. Also a func OggGetDuration() was implemented that returns duration of a song.

This commit is contained in:
Alexander Andreev 2023-10-02 01:08:24 +04:00
parent aaf14e0c83
commit 17eeebf1f3
Signed by: Arav
GPG Key ID: D22A817D95815393
2 changed files with 96 additions and 0 deletions

View File

@ -6,9 +6,57 @@ for certain tag names ending with an = character, e.g. artist= and title=.
import ( import (
"bytes" "bytes"
"io"
"os"
"strings" "strings"
"time"
) )
const bufferLength = 4096
const OggMagicSequence = "OggS"
const OggVorbisSequence = "vorbis"
// OggReadFile returns a head of an OGG file, and a buffer contains last frame.
func OggReadFile(path string) (buf_start, buf_end []byte, _ error) {
f, err := os.Open(path)
if err != nil {
return nil, nil, err
}
buf_start = make([]byte, bufferLength)
if _, err := f.Read(buf_start); err != nil {
return nil, nil, err
}
buf_end = make([]byte, bufferLength)
if _, err := f.Seek(-bufferLength, io.SeekEnd); err != nil {
return nil, nil, err
}
fst, err := f.Stat()
if err != nil {
return nil, nil, err
}
for offset := int64(bufferLength); offset <= fst.Size(); offset += bufferLength {
if _, err := f.Seek(-offset, io.SeekEnd); err != nil {
return nil, nil, err
}
if _, err := f.Read(buf_end); err != nil {
return nil, nil, err
}
if bytes.Contains(buf_end, []byte(OggMagicSequence)) {
break
}
}
return
}
// OggGetTag is searching for a certain tag in a given buffer buf and returns // OggGetTag is searching for a certain tag in a given buffer buf and returns
// its value. // its value.
// //
@ -29,3 +77,22 @@ func OggGetTag(buf []byte, tag string) string {
valLen := int(buf[tagIdx-4]) - tagNameLen valLen := int(buf[tagIdx-4]) - tagNameLen
return string(buf[valStart : valStart+valLen]) return string(buf[valStart : valStart+valLen])
} }
// OggGetDuration returns song's duration in milliseconds.
func OggGetDuration(buf_start, buf_end []byte) time.Duration {
rateIdx := bytes.Index(buf_start, []byte(OggVorbisSequence)) +
len(OggVorbisSequence) + 5
rateBytes := buf_start[rateIdx : rateIdx+4]
rate := int32(rateBytes[0]) + int32(rateBytes[1])<<8 +
int32(rateBytes[2])<<16 + int32(rateBytes[3])<<24
granuleIdx := bytes.LastIndex(buf_end, []byte(OggMagicSequence)) +
len(OggMagicSequence) + 2
granuleBytes := buf_end[granuleIdx : granuleIdx+8]
granule := int64(granuleBytes[0]) + int64(granuleBytes[1])<<8 +
int64(granuleBytes[2])<<16 + int64(granuleBytes[3])<<24 +
int64(granuleBytes[4])<<32 + int64(granuleBytes[5])<<40 +
int64(granuleBytes[6])<<48 + int64(granuleBytes[7])<<56
return time.Duration(granule*1000/int64(rate)) * time.Millisecond
}

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@ -1,6 +1,7 @@
package oggtag package oggtag
import ( import (
"bytes"
"os" "os"
"testing" "testing"
) )
@ -33,3 +34,31 @@ func BenchmarkOggGetTag(b *testing.B) {
OggGetTag(buf, "artist") OggGetTag(buf, "artist")
} }
} }
func TestOggReadFile(t *testing.T) {
bs, bf, err := OggReadFile(sampleSong)
if err != nil {
t.Error(err)
}
t.Log("bs = ", len(bs), "; bf =", len(bf), "bf(OggS) =", bytes.LastIndex(bf, []byte("OggS")))
}
func BenchmarkOggGetDuration(b *testing.B) {
bs, bf, err := OggReadFile(sampleSong)
if err != nil {
b.Error(err)
}
b.ResetTimer()
for i := 0; i < b.N; i++ {
OggGetDuration(bs, bf)
}
}
func TestOggGetDuration(t *testing.T) {
bs, bf, err := OggReadFile(sampleSong)
if err != nil {
t.Error(err)
}
t.Log(OggGetDuration(bs, bf))
}