Documentation

Overview

Package audio provides audio players.

The stream format must be 16-bit little endian and 2 channels. The format is as follows:

[data]      = [sample 1] [sample 2] [sample 3] ...
[sample *]  = [channel 1] ...
[channel *] = [byte 1] [byte 2] ...

An audio context (audio.Context object) has a sample rate you can specify and all streams you want to play must have the same sample rate. However, decoders in e.g. audio/mp3 package adjust sample rate automatically, and you don't have to care about it as long as you use those decoders.

An audio context can generate 'players' (audio.Player objects), and you can play sound by calling Play function of players. When multiple players play, mixing is automatically done. Note that too many players may cause distortion.

For the simplest example to play sound, see wav package in the examples.

Index

Constants

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Variables

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Functions

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Types

type Context

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

A Context represents a current state of audio.

At most one Context object can exist in one process. This means only one constant sample rate is valid in your one application.

For a typical usage example, see examples/wav/main.go.

func CurrentContext

func CurrentContext() *Context

CurrentContext returns the current context or nil if there is no context.

func NewContext

func NewContext(sampleRate int) *Context

NewContext creates a new audio context with the given sample rate.

The sample rate is also used for decoding MP3 with audio/mp3 package or other formats as the target sample rate.

sampleRate should be 44100 or 48000. Other values might not work. For example, 22050 causes error on Safari when decoding MP3.

NewContext panics when an audio context is already created.

func (*Context) IsReady

func (c *Context) IsReady() bool

IsReady returns a boolean value indicating whether the audio is ready or not.

On some browsers, user interaction like click or pressing keys is required to start audio.

func (*Context) SampleRate

func (c *Context) SampleRate() int

SampleRate returns the sample rate.

type InfiniteLoop

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

InfiniteLoop represents a looped stream which never ends.

func NewInfiniteLoop

func NewInfiniteLoop(src io.ReadSeeker, length int64) *InfiniteLoop

NewInfiniteLoop creates a new infinite loop stream with a source stream and length in bytes.

func NewInfiniteLoopWithIntro

func NewInfiniteLoopWithIntro(src io.ReadSeeker, introLength int64, loopLength int64) *InfiniteLoop

NewInfiniteLoopWithIntro creates a new infinite loop stream with an intro part. NewInfiniteLoopWithIntro accepts a source stream src, introLength in bytes and loopLength in bytes.

func (*InfiniteLoop) Read

func (i *InfiniteLoop) Read(b []byte) (int, error)

Read is implementation of ReadSeekCloser's Read.

func (*InfiniteLoop) Seek

func (i *InfiniteLoop) Seek(offset int64, whence int) (int64, error)

Seek is implementation of ReadSeekCloser's Seek.

type Player

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

Player is an audio player which has one stream.

Even when all references to a Player object is gone, the object is not GCed until the player finishes playing. This means that if a Player plays an infinite stream, the object is never GCed unless Close is called.

func NewPlayer

func NewPlayer(context *Context, src io.Reader) (*Player, error)

NewPlayer creates a new player with the given stream.

src's format must be linear PCM (16bits little endian, 2 channel stereo) without a header (e.g. RIFF header). The sample rate must be same as that of the audio context.

The player is seekable when src is io.Seeker. Attempt to seek the player that is not io.Seeker causes panic.

Note that the given src can't be shared with other Player objects.

NewPlayer tries to call Seek of src to get the current position. NewPlayer returns error when the Seek returns error.

A Player doesn't close src even if src implements io.Closer. Closing the source is src owner's responsibility.

func NewPlayerFromBytes

func NewPlayerFromBytes(context *Context, src []byte) *Player

NewPlayerFromBytes creates a new player with the given bytes.

As opposed to NewPlayer, you don't have to care if src is already used by another player or not. src can be shared by multiple players.

The format of src should be same as noted at NewPlayer.

func (*Player) Close

func (p *Player) Close() error

Close closes the stream.

When Close is called, the stream owned by the player is NOT closed, even if the stream implements io.Closer.

Close returns error when the player is already closed.

func (*Player) Current

func (p *Player) Current() time.Duration

Current returns the current position in time.

func (*Player) IsPlaying

func (p *Player) IsPlaying() bool

IsPlaying returns boolean indicating whether the player is playing.

func (*Player) Pause

func (p *Player) Pause()

Pause pauses the playing.

func (*Player) Play

func (p *Player) Play()

Play plays the stream.

func (*Player) Rewind

func (p *Player) Rewind() error

Rewind rewinds the current position to the start.

The passed source to NewPlayer must be io.Seeker, or Rewind panics.

Rewind returns error when seeking the source stream returns error.

func (*Player) Seek

func (p *Player) Seek(offset time.Duration) error

Seek seeks the position with the given offset.

The passed source to NewPlayer must be io.Seeker, or Seek panics.

Seek returns error when seeking the source stream returns error.

func (*Player) SetVolume

func (p *Player) SetVolume(volume float64)

SetVolume sets the volume of this player. volume must be in between 0 and 1. SetVolume panics otherwise.

func (*Player) Volume

func (p *Player) Volume() float64

Volume returns the current volume of this player [0-1].

Directories

Path Synopsis
internal/convert
mp3 Package mp3 provides MP3 decoder.
vorbis Package vorbis provides Ogg/Vorbis decoder.
wav Package wav provides WAV (RIFF) decoder.