Safe Haskell	None
Language	Haskell2010

Data.Conduit.Audio

Contents

Types
Generating audio
Combining audio
Editing audio
Utility functions

Description

A high-level functional interface for manipulating streams of audio.

Synopsis

Types

data AudioSource m a Source

An abstraction of a stream of audio. Inside is a Conduit Source which loads or generates smallish chunks of audio on demand. m is the Monad used by the Source to produce audio. a is the type of audio samples, contained in storable vectors (and thus should be Storable). Both (signed) Integral and Fractional sample types are supported.

Constructors

AudioSource

Fields

source :: Source m (Vector a): The stream of audio chunks; samples interleaved by channel. Each chunk can be any positive whole number of frames.
rate :: Rate
channels :: Channels
frames :: Frames: The stated length in frames of this audio stream. Not guaranteed to be exactly frame-accurate; the output of some operations like resampling or time-stretching may store only approximate frame counts.

type Seconds = Double Source

A duration in real time.

type Frames = Int Source

A frame consists of one sample for each audio channel.

type Rate = Double Source

The number of samples per second.

type Channels = Int Source

The number of audio channels (1 = mono, 2 = stereo, etc.)

data Duration Source

Used for functions that accept durations in either real time or audio frames.

Constructors

Seconds Seconds
Frames Frames

Instances

Eq Duration
Ord Duration
Read Duration
Show Duration

Generating audio

silent :: (Monad m, Num a, Storable a) => Duration -> Rate -> Channels -> AudioSource m a Source

Generates a stream of silence with the given parameters.

sine :: (Monad m, Floating a, Storable a) => a -> Duration -> Rate -> AudioSource m a Source

Generates a mono sine wave with the given frequency.

Combining audio

concatenate :: Monad m => AudioSource m a -> AudioSource m a -> AudioSource m a Source

Connects the end of the first audio source to the beginning of the second. The two sources must have the same sample rate and channel count.

mix :: (Monad m, Num a, Storable a) => AudioSource m a -> AudioSource m a -> AudioSource m a Source

Mixes two audio streams together by adding them samplewise. The two streams must have the same sample rate and channel count. It is recommended to only mix floating-point sample types. If you mix integral types and the result goes outside of the type's range, the result will not be a normal "clipping" effect, but will instead overflow, producing glitchy audio.

merge :: (Monad m, Num a, Storable a) => AudioSource m a -> AudioSource m a -> AudioSource m a Source

Combines the channels of two audio streams into a single source with all the channels. The two streams must have the same sample rate, but can have any number of channels.

splitChannels :: (Monad m, Storable a) => AudioSource m a -> [AudioSource m a] Source

Splits an audio stream into several, each providing a single channel of the original stream.

Editing audio

padStart :: (Monad m, Num a, Storable a) => Duration -> AudioSource m a -> AudioSource m a Source

Adds silence to the start of the audio stream.

padEnd :: (Monad m, Num a, Storable a) => Duration -> AudioSource m a -> AudioSource m a Source

Adds silence to the end of the audio stream.

takeStart :: (Monad m, Storable a) => Duration -> AudioSource m a -> AudioSource m a Source

Takes no more than the given duration of audio from the start of the stream.

takeEnd :: (Monad m, Storable a) => Duration -> AudioSource m a -> AudioSource m a Source

Takes no more than the given duration of audio from the end of the stream. This function relies on the frames value stored with the stream.

dropStart :: (Monad m, Storable a) => Duration -> AudioSource m a -> AudioSource m a Source

Drops the given duration of audio from the start of the stream.

dropEnd :: (Monad m, Storable a) => Duration -> AudioSource m a -> AudioSource m a Source

Drops the given duration of audio from the end of the stream. This function relies on the frames value stored with the stream.

fadeIn :: (Monad m, Ord a, Fractional a, Storable a) => AudioSource m a -> AudioSource m a Source

Fades the audio from start (silent) to end (original volume). This function relies on the frames value stored with the stream.

fadeOut :: (Monad m, Ord a, Fractional a, Storable a) => AudioSource m a -> AudioSource m a Source

Fades the audio from start (original volume) to end (silent). This function relies on the frames value stored with the stream.

mapSamples :: (Monad m, Storable a, Storable b) => (a -> b) -> AudioSource m a -> AudioSource m b Source

Applies a function to every sample in the audio stream.

gain :: (Monad m, Num a, Storable a) => a -> AudioSource m a -> AudioSource m a Source

Multiplies all the audio samples by the given scaling factor. It is best to use this function on floating-point sample types, for the same reasons that apply to mix.

Utility functions

vectorFrames :: Storable a => Vector a -> Channels -> Frames Source

Divides the vector length by the channel count to calculate the number of audio frames.

framesToSeconds :: Frames -> Rate -> Seconds Source

Uses the sample rate to convert frames to seconds.

secondsToFrames :: Seconds -> Rate -> Frames Source

Uses the sample rate to convert seconds to frames, rounding if necessary.

chunkSize :: Frames Source

An arbitrary size, in frames, for smallish audio chunks.

deinterleave :: Storable a => Channels -> Vector a -> [Vector a] Source

Given a vector with interleaved samples, like [L0, R0, L1, R1, ...], converts it into [[L0, L1, ...], [R0, R1, ...]].

interleave :: Storable a => [Vector a] -> Vector a Source

Opposite of deinterleave. All the input vectors should have the same length.

integralSample :: (RealFrac a, Integral b, Bounded b) => a -> b Source

Converts fractional samples in the range [-1, 1] to integral samples in a two's-complement type. Fractional samples beyond that range are clamped.

fractionalSample :: (Integral a, Bounded a, Fractional b) => a -> b Source

Converts integral samples in a two's-complement type to fractional samples in the range [-1, 1].