aio

package module
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 Go to latest Published: Dec 29, 2022 License: MIT Imports: 15 Imported by: 2

README

aio

A simple Audio I/O library written in Go. This library relies on FFmpeg, FFProbe and FFPlay which must be downloaded before usage and added to the system path.

For Video I/O using FFmpeg. see the Vidio project.

Installation

go get github.com/AlexEidt/aio

Buffers

aio uses byte buffers to transport raw audio data. Audio data can take on many forms, including floating point, unsigned integer and signed integer. These types may be larger than a byte and would have to be split. Valid formats are u8, s8, u16, s16, u24, s24, u32, s32, f32, and f64. These represent u unsigned integers, s signed integers and f floating point numbers.

As an example, if there is stereo sound (two channels) encoded in the s16 (signed 16 bit integers) format with a sampling rate of 44100 Hz, one second of audio would be

44100 * 2 (channels) * 2 (bytes per sample) = 176400 bytes

Continuing on with this example, since this is stereo audio with 2 channels, one frame of audio is represented by 2 consecutive integers, one for each channel. Each integer is 16 bits, which means one frame of audio would be represented by 4 consecutive bytes.

Options

The Options struct is used to specify optional parameters for Audio I/O.

type Options struct {
	Stream     int    // Audio Stream Index to use.
	SampleRate int    // Sample rate in Hz.
	Channels   int    // Number of channels.
	Bitrate    int    // Bitrate in bits/s.
	Format     string // Format of audio.
	Codec      string // Audio Codec.
	StreamFile string // File path for extra stream data.
}

The Options.StreamFile parameter is intended for users who wish to alter an audio stream from a video. Instead of having to process the audio and store in a file and then combine with the video later, the user can simply pass in the original video file path via the Options.StreamFile parameter. This will combine the audio with all other streams in the given video file (Video, Subtitle, Data, and Attachments Streams) and will cut all streams to be the same length. Note that aio is not a audio/video editing library.

This means that adding extra stream data from a file will only work if the filename being written to is a container format, i.e attempting to add video streams to a wav file will result in undefined behavior.

Audio

Audio is used to read audio from files. It can also be used to gather audio metadata from a file. By default, the audio buffer has a length of

sample rate * channels * bytes per sample

which corresponds to 1 second of audio data.

The user may pass in options to set the desired sampling rate, format and channels of the audio. If options is nil, then the channels and sampling rate from the file will be used, with a default format of s16.

The Read() function fills the internal byte buffer with the next batch of audio samples. Once the entire file has been read, Read() will return false and close the Audio struct.

Note that the Samples() function is only present for convenience. It casts the raw byte buffer into the given audio data type determined by the Format() such that the underlying data buffers are the same. The s24 and u24 formats are not supported by the Samples() function since there is no type equivalent. Calling the Samples() function on 24-bit audio will return the raw byte buffer.

The return value of the Samples() function will have to be cast into an array of the desired type (e.g. audio.Samples().([]float32))

aio.NewAudio(filename string, options *aio.Options) (*aio.Audio, error)
aio.NewAudioStreams(filename string, options *aio.Options) ([]*aio.Audio, error)

FileName() string
SampleRate() int
Channels() int
Bitrate() int
BitsPerSample() int
Stream() int
Total() int
Duration() float64
Format() string
Codec() string
HasStreams() bool
Buffer() []byte
MetaData() map[string]string
Samples() interface{}
SetBuffer(buffer []byte) error

Read() bool
Close()

AudioWriter

AudioWriter is used to write audio to files from a buffer of audio samples. It comes with an Options struct that can be used to specify certain metadata of the output audio file. If options is nil, the defaults used are a sampling rate of 44100 Hz, with 2 channels in the s16 format.

aio.NewAudioWriter(filename string, options *aio.Options) (*aio.AudioWriter, error)

FileName() string
StreamFile() string
SampleRate() int
Channels() int
Bitrate() int
Format() string
Codec() string

Write(samples interface{}) error
Close()

Microphone

Microphone is similar to the Audio struct, the only difference being that it reads audio from the microphone. The stream parameter is used to specify the microphone stream index, which will differ depending on the platform. For Windows (dshow) and MacOS (avfoundation), find the stream index by entering the following command

ffmpeg -f [dshow | avfoundation] -list_devices true -i dummy

and selecting the desired stream. For linux, see this page on the FFmpeg Wiki.

Additionally, an options parameter may be passed to specify the format, sampling rate and audio channels the microphone should record at. Any other options are ignored.

aio.NewMicrophone(stream int, options *aio.Options) (*aio.Microphone, error)

Name() string
SampleRate() int
Channels() int
BitsPerSample() int
Format() string
Buffer() []byte
Samples() interface{}
SetBuffer(buffer []byte) error

Read() bool
Close()

Player

Player is used to play audio from a buffer of audio samples.

aio.NewPlayer(channels, samplerate int, format string) (*aio.Player, error)

SampleRate() int
Channels() int
Format() string
Play(samples interface{}) error
Close()

Examples

Copy input.wav to output.mp3.

audio, _ := aio.NewAudio("input.wav", nil)

options := aio.Options{
	SampleRate: audio.SampleRate(),
	Channels:   audio.Channels(),
	Bitrate:    audio.Bitrate(),
	Format:     audio.Format(),
}

writer, _ := aio.NewAudioWriter("output.mp3", &options)
defer writer.Close()

for audio.Read() {
	writer.Write(audio.Buffer())
}

Capture 10 seconds of audio from the microphone. Audio is recorded at 44100 Hz stereo and is in signed 16 bit format.

micOptions := aio.Options{Format: "s16", Channels: 2, SampleRate: 44100}
mic, _ := aio.NewMicrophone(0, &micOptions)
defer mic.Close()

writerOptions := aio.Options{
	SampleRate: mic.SampleRate(),
	Channels:   mic.Channels(),
	Format:     mic.Format(),
}

writer, _ := aio.NewAudioWriter("output.wav", &writerOptions)
defer writer.Close()

seconds := 0
for mic.Read() && seconds < 10 {
	writer.Write(mic.Buffer())
	seconds++
}

Play all audio tracks from input.mp4 sequentially.

streams, _ := aio.NewAudioStreams("input.mp4", nil)

for _, stream := range streams {
	player, _ := aio.NewPlayer(stream.Channels(), stream.SampleRate(), stream.Format())
	for stream.Read() {
		player.Play(stream.Buffer())
	}
	player.Close()
}

Play input.mp4.

audio, _ := aio.NewAudio("input.mp4", nil)
player, _ := aio.NewPlayer(audio.Channels(), audio.SampleRate(), audio.Format())
defer player.Close()

for audio.Read() {
	player.Play(audio.Buffer())
}

Read input.wav and process the audio samples.

audio, _ := aio.NewAudio("input.wav", nil)

for audio.Read() {
	samples := audio.Samples().([]int16)
	for i := range samples {
		// audio processing...
	}
}

Combine sound.wav and movie.mov into output.mp4.

audio, _ := aio.NewAudio("sound.wav", nil)

options := aio.Options{
	SampleRate: audio.SampleRate(),
	Channels:   audio.Channels(),
	Bitrate:    audio.Bitrate(),
	Format:     audio.Format(),
	Codec:      "aac",
	StreamFile: "movie.mov",
}

writer, _ := aio.NewAudioWriter("output.mp4", &options)
defer writer.Close()

for audio.Read() {
	writer.Write(audio.Buffer())
}

Play Microphone audio. Use default microphone settings for recording.

mic, _ := aio.NewMicrophone(0, nil)
defer mic.Close()

player, _ := aio.NewPlayer(mic.Channels(), mic.SampleRate(), mic.Format())
defer player.Close()

for mic.Read() {
	player.Play(mic.Buffer())
}

Documentation

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type Audio 

type Audio struct {
	// contains filtered or unexported fields
}

func NewAudio 

func NewAudio(filename string, options *Options) (*Audio, error)

func NewAudioStreams added in v1.3.0 

func NewAudioStreams(filename string, options *Options) ([]*Audio, error)

Read all audio streams from the given file.

func (*Audio) Bitrate 

func (audio *Audio) Bitrate() int

Audio Bitrate in bits/s.

func (*Audio) BitsPerSample 

func (audio *Audio) BitsPerSample() int

func (*Audio) Buffer 

func (audio *Audio) Buffer() []byte

func (*Audio) Channels 

func (audio *Audio) Channels() int

func (*Audio) Close 

func (audio *Audio) Close()

Closes the pipe and stops the ffmpeg process.

func (*Audio) Codec 

func (audio *Audio) Codec() string

func (*Audio) Duration 

func (audio *Audio) Duration() float64

Audio Duration in seconds.

func (*Audio) FileName 

func (audio *Audio) FileName() string

func (*Audio) Format 

func (audio *Audio) Format() string

func (*Audio) HasStreams added in v1.4.0 

func (audio *Audio) HasStreams() bool

Returns true if file has any video, subtitle, data or attachment streams.

func (*Audio) MetaData added in v1.3.0 

func (audio *Audio) MetaData() map[string]string

Raw Metadata from ffprobe output for the audio file.

func (*Audio) Read 

func (audio *Audio) Read() bool

Reads the next frame of audio and stores it in the buffer. If the last audio frame has been read, returns false, otherwise true.

func (*Audio) SampleRate 

func (audio *Audio) SampleRate() int

Audio Sample Rate in Hz.

func (*Audio) Samples added in v1.1.0 

func (audio *Audio) Samples() interface{}

Casts the values in the byte buffer to those specified by the audio format.

func (*Audio) SetBuffer 

func (audio *Audio) SetBuffer(buffer []byte) error

Sets the buffer to the given byte array. The length of the buffer must be a multiple of (bytes per sample * audio channels).

func (*Audio) Stream added in v1.3.0 

func (audio *Audio) Stream() int

Returns the zero-indexed audio stream index.

func (*Audio) Total added in v1.2.3 

func (audio *Audio) Total() int

Returns the total number of audio samples in the file in bytes.

type AudioWriter 

type AudioWriter struct {
	// contains filtered or unexported fields
}

func NewAudioWriter 

func NewAudioWriter(filename string, options *Options) (*AudioWriter, error)

func (*AudioWriter) Bitrate 

func (writer *AudioWriter) Bitrate() int

Audio Bitrate in bits/s.

func (*AudioWriter) Channels 

func (writer *AudioWriter) Channels() int

func (*AudioWriter) Close 

func (writer *AudioWriter) Close()

Closes the pipe and stops the ffmpeg process.

func (*AudioWriter) Codec 

func (writer *AudioWriter) Codec() string

func (*AudioWriter) FileName 

func (writer *AudioWriter) FileName() string

func (*AudioWriter) Format 

func (writer *AudioWriter) Format() string

func (*AudioWriter) SampleRate 

func (writer *AudioWriter) SampleRate() int

Audio Sample Rate in Hz.

func (*AudioWriter) StreamFile added in v1.4.0 

func (writer *AudioWriter) StreamFile() string

File used to fill in extra stream data.

func (*AudioWriter) Write 

func (writer *AudioWriter) Write(samples interface{}) error

Writes the given samples to the audio file.

type Microphone 

type Microphone struct {
	// contains filtered or unexported fields
}

func NewMicrophone 

func NewMicrophone(stream int, options *Options) (*Microphone, error)

func (*Microphone) BitsPerSample 

func (mic *Microphone) BitsPerSample() int

func (*Microphone) Buffer 

func (mic *Microphone) Buffer() []byte

func (*Microphone) Channels 

func (mic *Microphone) Channels() int

func (*Microphone) Close 

func (mic *Microphone) Close()

Closes the pipe and stops the ffmpeg process.

func (*Microphone) Format 

func (mic *Microphone) Format() string

func (*Microphone) Name 

func (mic *Microphone) Name() string

func (*Microphone) Read 

func (mic *Microphone) Read() bool

Reads the next frame from of audio and stores it in the buffer. If the last frame has been read, returns false, otherwise true.

func (*Microphone) SampleRate 

func (mic *Microphone) SampleRate() int

Audio Sample Rate in Hz.

func (*Microphone) Samples added in v1.1.0 

func (mic *Microphone) Samples() interface{}

func (*Microphone) SetBuffer 

func (mic *Microphone) SetBuffer(buffer []byte) error

Sets the buffer to the given byte array. The length of the buffer must be a multiple of (bytes per sample * audio channels).

type Options 

type Options struct {
	Stream     int    // Audio Stream Index to use.
	SampleRate int    // Sample rate in Hz.
	Channels   int    // Number of channels.
	Bitrate    int    // Bitrate in bits/s.
	Format     string // Format of audio.
	Codec      string // Audio Codec.
	StreamFile string // File path for extra stream data.
}

type Player 

type Player struct {
	// contains filtered or unexported fields
}

func NewPlayer 

func NewPlayer(channels, samplerate int, format string) (*Player, error)

func (*Player) Channels added in v1.2.1 

func (player *Player) Channels() int

func (*Player) Close 

func (player *Player) Close()

Closes the pipe and stops the ffplay process.

func (*Player) Format added in v1.2.1 

func (player *Player) Format() string

func (*Player) Play 

func (player *Player) Play(samples interface{}) error

func (*Player) SampleRate added in v1.2.1 

func (player *Player) SampleRate() int

Source Files

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