mp3

Documentation

Index

• Constants
• Variables
• type ApeTag
• type AudioFrame
• type ID3v2Tag
• type MP3Info
  • func InspectFile(path string) (*MP3Info, error)
• type MPEGLayer
• type MPEGVersion
• type Scanner
  • func NewMP3Scanner(f io.ReadSeeker) (*Scanner, error)
  • func NewScanner(f io.ReadSeeker, version MPEGVersion, layer MPEGLayer) (*Scanner, error)
  • func (s *Scanner) NextFrame() (*AudioFrame, uint64, error)

Constants

const (
	STEREO         = iota
	JOINT_STEREO   // stereo
	DUAL_CHANNE    // two mono chans
	SINGLE_CHANNEL // mono
)

Variables

var APEHeader = []byte{'A', 'P', 'E', 'T'}

var BitrateLookupTable = [][][]uint64{
	MPEG2BitrateTable,
	{ZeroedBitrates, ZeroedBitrates, ZeroedBitrates, ZeroedBitrates},
	MPEG2BitrateTable,
	MPEG1BitrateTable,
}

Lookup by Version, Layer, and Bitrate Index

var ID3v1Header = []byte{'T', 'A', 'G'}

var ID3v1Size = 128

var ID3v2Header = []byte{'I', 'D', '3'}

var MPEG1BitrateTable = [][]uint64{
	ZeroedBitrates,
	{0, 32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 0},
	{0, 32, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 0},
	{0, 32, 64, 96, 128, 160, 192, 224, 256, 288, 320, 352, 384, 416, 448, 0},
}

var MPEG2BitrateTable = [][]uint64{
	ZeroedBitrates,
	MPEG2L2L3Bitrates,
	MPEG2L2L3Bitrates,
	MPEG2L1Bitrates,
}

var MPEG2L1Bitrates = []uint64{0, 32, 48, 56, 64, 80, 96, 112, 128, 144, 160, 176, 192, 224, 256, 0}

var MPEG2L2L3Bitrates = []uint64{0, 8, 16, 24, 32, 40, 48, 56, 64, 80, 96, 112, 128, 144, 160, 0}

var SamplerateLookupTable = [][]uint64{
	{11025, 12000, 8000, 0},
	{0, 0, 0, 0},
	{22050, 24000, 16000, 0},
	{44100, 48000, 32000, 0},
}

Lookup by Version, Samplerate Index

var SamplesLookupTable = [][]uint64{
	{0, 576, 1152, 384},
	{0, 0, 0, 0},
	{0, 576, 1152, 384},
	{0, 1152, 1152, 384},
}

Lookup by Version, Layer

var ZeroedBitrates = []uint64{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}

Types

type ApeTag

type ApeTag struct {
	Version  uint32
	Size     uint32
	NumItems uint32
	Flags    uint32
}

type AudioFrame

type AudioFrame struct {
	Version         MPEGVersion
	Layer           MPEGLayer
	CRC             bool
	BitrateIndex    uint8
	SamplerateIndex uint8
	Padding         uint8
	Private         bool
	Mode            uint8
	ModeExt         uint8
	Copyright       bool
	Original        bool
	Emphasis        uint8

	Bitrate    uint64
	Samplerate uint64

	Size uint64
}

information about one mp3 audio frame

type ID3v2Tag

type ID3v2Tag struct {
	Version  uint8
	Revision uint8
	Flags    uint16
	Size     uint32
}

type MP3Info

type MP3Info struct {
	Bitrate       uint64
	IsVBR         bool
	HasXingHeader bool
	HasVBRiHeader bool

	Samplerate uint64

	Duration time.Duration

	HasID3v1 bool
	ID3v2    *ID3v2Tag
	Ape      *ApeTag

	FoundLayer1 bool
	FoundLayer2 bool
	FoundLayer3 bool

	FoundMPEG1  bool
	FoundMPEG2  bool
	FoundMPEG25 bool

	UnknownBytes uint64

	FrameCount   int
	StartGarbage int64
}

func InspectFile

func InspectFile(path string) (*MP3Info, error)

type MPEGLayer

type MPEGLayer int

const (
	LAYER_RESERVED MPEGLayer = iota
	LAYER3
	LAYER2
	LAYER1
)

type MPEGVersion

type MPEGVersion int

const (
	MPEG25 MPEGVersion = iota
	MPEG_RESERVED
	MPEG2
	MPEG1
)

type Scanner

type Scanner struct {
	FrameCount int

	Info *MP3Info
	// contains filtered or unexported fields
}

func NewMP3Scanner

func NewMP3Scanner(f io.ReadSeeker) (*Scanner, error)

func NewScanner

func NewScanner(f io.ReadSeeker, version MPEGVersion, layer MPEGLayer) (*Scanner, error)

func (*Scanner) NextFrame

func (s *Scanner) NextFrame() (*AudioFrame, uint64, error)