audio

package module
v1.0.0 Latest Latest
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 Go to latest Published: Oct 13, 2018 License: Apache-2.0 Imports: 2 Imported by: 219

README

audio

GoDoc

audio is a generic Go package designed to define a common interface to analyze and/or process audio data.

At the heart of the package is the Buffer interface and its implementations:

  • FloatBuffer
  • Float32Buffer
  • IntBuffer

Decoders, encoders, processors, analyzers and transformers can be written to accept or return these types and share a common interface.

The idea is that audio libraries can define this interface or its implementations as input and return an audio.Buffer interface allowing all audio libraries to be chainable.

Performance

The buffer implementations are designed so a buffer can be reused and mutated avoiding allocation penalties.

It is recommended to avoid using Float32Buffer unless performance is critical. The major drawback of using float32s is that the Go stdlib was designed to work with float64 and therefore the access to standard packages is limited.

Usage

Examples of how to use this interface is available under the go-audio organization.

Documentation

Overview

Package audio defines a common interface to analyze and/or process audio data.

At the heart of the package is the Buffer interface and its implementations: FloatBuffer and IntBuffer. Decoders, encoders, processors, analyzers and transformers can be written to accept or return these types and share a common interface.

Index

Constants

This section is empty.

Variables

View Source 
var (

	// FormatMono22500 is mono 22.5kHz format.
	FormatMono22500 = &Format{
		NumChannels: 1,
		SampleRate:  22500,
	}
	// FormatMono44100 is mono 8bit 44.1kHz format.
	FormatMono44100 = &Format{
		NumChannels: 1,
		SampleRate:  44100,
	}
	// FormatMono48000 is mono 48kHz format.
	FormatMono48000 = &Format{
		NumChannels: 1,
		SampleRate:  48000,
	}
	// FormatMono96000 is mono 96kHz format.
	FormatMono96000 = &Format{
		NumChannels: 1,
		SampleRate:  96000,
	}

	// FormatStereo22500 is stereo 22.5kHz format.
	FormatStereo22500 = &Format{
		NumChannels: 2,
		SampleRate:  22500,
	}
	// FormatStereo44100 is stereo 8bit 44.1kHz format.
	FormatStereo44100 = &Format{
		NumChannels: 2,
		SampleRate:  44100,
	}
	// FormatStereo48000 is stereo 48kHz format.
	FormatStereo48000 = &Format{
		NumChannels: 2,
		SampleRate:  48000,
	}
	// FormatStereo96000 is stereo 96kHz format.
	FormatStereo96000 = &Format{
		NumChannels: 2,
		SampleRate:  96000,
	}
)
View Source 
var (
	// ErrInvalidBuffer is a generic error returned when trying to read/write to an invalid buffer.
	ErrInvalidBuffer = errors.New("invalid buffer")
)

Functions

func IEEEFloatToInt 

func IEEEFloatToInt(b [10]byte) int

IEEEFloatToInt converts a 10 byte IEEE float into an int.

func Int24BETo32 

func Int24BETo32(bytes []byte) int32

Int24BETo32 converts an int24 value from 3 bytes into an int32 value

func Int24LETo32 

func Int24LETo32(bytes []byte) int32

Int24LETo32 converts an int24 value from 3 bytes into an int32 value

func Int32toInt24BEBytes 

func Int32toInt24BEBytes(n int32) []byte

Int32toInt24BEBytes converts an int32 into a big endian 3 byte int24 representation

func Int32toInt24LEBytes 

func Int32toInt24LEBytes(n int32) []byte

Int32toInt24LEBytes converts an int32 into a little endian 3 byte int24 representation

func IntMaxSignedValue 

func IntMaxSignedValue(b int) int

IntMaxSignedValue returns the max value of an integer based on its memory size

func IntToIEEEFloat 

func IntToIEEEFloat(i int) [10]byte

IntToIEEEFloat converts an int into a 10 byte IEEE float.

func Uint24to32 

func Uint24to32(bytes []byte) uint32

Uint24to32 converts a 3 byte uint23 into a uint32 BigEndian!

func Uint32toUint24Bytes 

func Uint32toUint24Bytes(n uint32) []byte

Uint32toUint24Bytes converts a uint32 into a 3 byte uint24 representation

Types

type Buffer 

type Buffer interface {
	// PCMFormat is the format of buffer (describing the buffer content/format).
	PCMFormat() *Format
	// NumFrames returns the number of frames contained in the buffer.
	NumFrames() int
	// AsFloatBuffer returns a float 64 buffer from this buffer.
	AsFloatBuffer() *FloatBuffer
	// AsFloat32Buffer returns a float 32 buffer from this buffer.
	AsFloat32Buffer() *Float32Buffer
	// AsIntBuffer returns an int buffer from this buffer.
	AsIntBuffer() *IntBuffer
	// Clone creates a clean clone that can be modified without
	// changing the source buffer.
	Clone() Buffer
}

Buffer is the representation of an audio buffer.

type Float32Buffer 

type Float32Buffer struct {
	// Format is the representation of the underlying data format
	Format *Format
	// Data is the buffer PCM data as floats
	Data []float32
	// SourceBitDepth helps us know if the source was encoded on
	// 8, 16, 24, 32, 64 bits.
	SourceBitDepth int
}

Float32Buffer is an audio buffer with its PCM data formatted as float32.

func (*Float32Buffer) AsFloat32Buffer 

func (buf *Float32Buffer) AsFloat32Buffer() *Float32Buffer

AsFloat32Buffer implements the Buffer interface and returns itself.

func (*Float32Buffer) AsFloatBuffer 

func (buf *Float32Buffer) AsFloatBuffer() *FloatBuffer

AsFloatBuffer implements the Buffer interface and returns a float64 version of itself.

func (*Float32Buffer) AsIntBuffer 

func (buf *Float32Buffer) AsIntBuffer() *IntBuffer

AsIntBuffer returns a copy of this buffer but with data truncated to Ints. It is usually recommended to apply a transforms when going from a 24bit source to an int (16bit destination). Look at transforms.PCMScaleF32() for instance

func (*Float32Buffer) Clone 

func (buf *Float32Buffer) Clone() Buffer

Clone creates a clean clone that can be modified without changing the source buffer.

func (*Float32Buffer) NumFrames 

func (buf *Float32Buffer) NumFrames() int

NumFrames returns the number of frames contained in the buffer.

func (*Float32Buffer) PCMFormat 

func (buf *Float32Buffer) PCMFormat() *Format

PCMFormat returns the buffer format information.

type FloatBuffer 

type FloatBuffer struct {
	// Format is the representation of the underlying data format
	Format *Format
	// Data is the buffer PCM data as floats
	Data []float64
}

FloatBuffer is an audio buffer with its PCM data formatted as float64.

func (*FloatBuffer) AsFloat32Buffer 

func (buf *FloatBuffer) AsFloat32Buffer() *Float32Buffer

AsFloat32Buffer implements the Buffer interface and returns a float 32 version of itself.

func (*FloatBuffer) AsFloatBuffer 

func (buf *FloatBuffer) AsFloatBuffer() *FloatBuffer

AsFloatBuffer implements the Buffer interface and returns itself.

func (*FloatBuffer) AsIntBuffer 

func (buf *FloatBuffer) AsIntBuffer() *IntBuffer

AsIntBuffer returns a copy of this buffer but with data truncated to Ints.

func (*FloatBuffer) Clone 

func (buf *FloatBuffer) Clone() Buffer

Clone creates a clean clone that can be modified without changing the source buffer.

func (*FloatBuffer) NumFrames 

func (buf *FloatBuffer) NumFrames() int

NumFrames returns the number of frames contained in the buffer.

func (*FloatBuffer) PCMFormat 

func (buf *FloatBuffer) PCMFormat() *Format

PCMFormat returns the buffer format information.

type Format 

type Format struct {
	// NumChannels is the number of channels contained in the data
	NumChannels int
	// SampleRate is the sampling rate in Hz
	SampleRate int
}

Format is a high level representation of the underlying data.

type IntBuffer 

type IntBuffer struct {
	// Format is the representation of the underlying data format
	Format *Format
	// Data is the buffer PCM data as ints
	Data []int
	// SourceBitDepth helps us know if the source was encoded on
	// 8, 16, 24, 32, 64 bits.
	SourceBitDepth int
}

IntBuffer is an audio buffer with its PCM data formatted as int.

func (*IntBuffer) AsFloat32Buffer 

func (buf *IntBuffer) AsFloat32Buffer() *Float32Buffer

AsFloat32Buffer returns a copy of this buffer but with data converted to float 32.

func (*IntBuffer) AsFloatBuffer 

func (buf *IntBuffer) AsFloatBuffer() *FloatBuffer

AsFloatBuffer returns a copy of this buffer but with data converted to floats.

func (*IntBuffer) AsIntBuffer 

func (buf *IntBuffer) AsIntBuffer() *IntBuffer

AsIntBuffer implements the Buffer interface and returns itself.

func (*IntBuffer) Clone 

func (buf *IntBuffer) Clone() Buffer

Clone creates a clean clone that can be modified without changing the source buffer.

func (*IntBuffer) NumFrames 

func (buf *IntBuffer) NumFrames() int

NumFrames returns the number of frames contained in the buffer.

func (*IntBuffer) PCMFormat 

func (buf *IntBuffer) PCMFormat() *Format

PCMFormat returns the buffer format information.

type PCMBuffer 

type PCMBuffer struct {
	// Format describes the format of the buffer data.
	Format *Format
	// I8 is a store for audio sample data as integers.
	I8 []int8
	// I16 is a store for audio sample data as integers.
	I16 []int16
	// I32 is a store for audio sample data as integers.
	I32 []int32
	// F32 is a store for audio samples data as float64.
	F32 []float32
	// F64 is a store for audio samples data as float64.
	F64 []float64
	// DataType indicates the primary format used for the underlying data.
	// The consumer of the buffer might want to look at this value to know what store
	// to use to optimaly retrieve data.
	DataType PCMDataFormat
	// SourceBitDepth helps us know if the source was encoded on
	// 1 (int8), 2 (int16), 3(int24), 4(int32), 8(int64) bytes.
	SourceBitDepth uint8
}

PCMBuffer encapsulates uncompressed audio data and provides useful methods to read/manipulate this PCM data. It's a more flexible buffer type allowing the developer to handle different kind of buffer data formats and convert between underlying types.

func (*PCMBuffer) AsF32 

func (b *PCMBuffer) AsF32() (out []float32)

AsF32 returns the buffer's samples as float32 sample values. If the buffer isn't in this format, a copy is created and converted. Note that converting might result in unexpected truncations.

func (*PCMBuffer) AsF64 

func (b *PCMBuffer) AsF64() (out []float64)

AsF64 returns the buffer's samples as float64 sample values. If the buffer isn't in this format, a copy is created and converted. Note that converting might result in unexpected truncations.

func (*PCMBuffer) AsFloat32Buffer 

func (b *PCMBuffer) AsFloat32Buffer() *Float32Buffer

AsFloat32Buffer implements the Buffer interface and returns a float 32 version of itself.

func (*PCMBuffer) AsFloatBuffer 

func (b *PCMBuffer) AsFloatBuffer() *FloatBuffer

AsFloatBuffer returns a copy of this buffer but with data converted to floats.

func (*PCMBuffer) AsI16 

func (b *PCMBuffer) AsI16() (out []int16)

AsI16 returns the buffer's samples as int16 sample values. If the buffer isn't in this format, a copy is created and converted. Note that converting might result in loss of resolution.

func (*PCMBuffer) AsI32 

func (b *PCMBuffer) AsI32() (out []int32)

AsI32 returns the buffer's samples as int32 sample values. If the buffer isn't in this format, a copy is created and converted. Note that converting a float to an int might result in unexpected truncations.

func (*PCMBuffer) AsI8 

func (b *PCMBuffer) AsI8() (out []int8)

AsI8 returns the buffer's samples as int8 sample values. If the buffer isn't in this format, a copy is created and converted. Note that converting might result in loss of resolution.

func (*PCMBuffer) AsInt 

func (b *PCMBuffer) AsInt() (out []int)

AsInt returns the buffer content as integers (int32s). It's recommended to avoid this method since it creates an extra copy of the buffer content.

func (*PCMBuffer) AsIntBuffer 

func (b *PCMBuffer) AsIntBuffer() *IntBuffer

AsIntBuffer returns a copy of this buffer but with data truncated to Ints.

func (*PCMBuffer) Clone 

func (b *PCMBuffer) Clone() Buffer

Clone creates a clean clone that can be modified without changing the source buffer.

func (*PCMBuffer) Len 

func (b *PCMBuffer) Len() int

Len returns the length of the underlying data.

func (*PCMBuffer) NumFrames 

func (b *PCMBuffer) NumFrames() int

NumFrames returns the number of frames contained in the buffer.

func (*PCMBuffer) PCMFormat 

func (b *PCMBuffer) PCMFormat() *Format

PCMFormat returns the buffer format information.

func (*PCMBuffer) SwitchPrimaryType 

func (b *PCMBuffer) SwitchPrimaryType(t PCMDataFormat)

SwitchPrimaryType is a convenience method to switch the primary data type. Use this if you process/swap a different type than the original type. Notes that conversion might be lossy if you switch to a lower resolution format.

type PCMDataFormat 

type PCMDataFormat uint8

PCMDataFormat is an enum type to indicate the underlying data format used. 

const (
	// DataTypeUnknown refers to an unknown format
	DataTypeUnknown PCMDataFormat = iota
	// DataTypeI8 indicates that the content of the audio buffer made of 8-bit integers.
	DataTypeI8
	// DataTypeI16 indicates that the content of the audio buffer made of 16-bit integers.
	DataTypeI16
	// DataTypeI32 indicates that the content of the audio buffer made of 32-bit integers.
	DataTypeI32
	// DataTypeF32 indicates that the content of the audio buffer made of 32-bit floats.
	DataTypeF32
	// DataTypeF64 indicates that the content of the audio buffer made of 64-bit floats.
	DataTypeF64
)

Source Files

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