| Copyright | (c) Thomas Tuegel 2011 |
|---|---|
| License | BSD |
| Maintainer | Thomas Tuegel <ttuegel@gmail.com> |
| Stability | experimental |
| Portability | non-portable (Linux only) |
| Safe Haskell | Safe |
| Language | Haskell98 |
Sound.ALSA.Mixer
Description
This library provides bindings to the Advanced Linux Sound Architecture
(ALSA) library API. The portability of this library is limited to
systems with ALSA (i.e., Linux systems). The functions in this library
throw errors of type T on failure.
Synopsis
- data Control = Control {}
- data Mixer
- data Channel
- data PerChannel e
- = Joined {
- getJoined :: IO e
- setJoined :: e -> IO ()
- joinedChannels :: [Channel]
- | PerChannel {
- getPerChannel :: IO [(Channel, e)]
- setPerChannel :: [(Channel, e)] -> IO ()
- perChannels :: [Channel]
- = Joined {
- data Volume = Volume {
- getRange :: IO (CLong, CLong)
- setRange :: (CLong, CLong) -> IO ()
- getRangeDb :: IO (CLong, CLong)
- value :: PerChannel CLong
- dB :: PerChannel CLong
- type Switch = PerChannel Bool
- data CUInt
- data CLong
- controls :: Mixer -> IO [Control]
- withMixer :: String -> (Mixer -> IO a) -> IO a
- getControlByName :: Mixer -> String -> IO (Maybe Control)
- common :: Either a (Maybe a, Maybe a) -> Maybe a
- playback :: Either a (Maybe a, Maybe a) -> Maybe a
- capture :: Either a (Maybe a, Maybe a) -> Maybe a
- channels :: PerChannel e -> [Channel]
- allChannels :: [Channel]
- joined :: PerChannel e -> Bool
- perChannel :: PerChannel e -> Bool
- getChannel :: Channel -> PerChannel x -> IO (Maybe x)
- setChannel :: Channel -> PerChannel x -> x -> IO ()
Types
Control represents one of the controls belonging to an ALSA mixer
element. Each control has a number of playback and capture channels.
The control may also have a switch and/or a volume capability associated
with it. The capability can be common to both playback and capture, or
there can be separate capabilities for each.
Constructors
| Unknown | |
| FrontLeft | |
| SND_MIXER_SCHN_MONO | |
| FrontRight | |
| RearLeft | |
| RearRight | |
| FrontCenter | |
| Woofer | |
| SideLeft | |
| SideRight | |
| RearCenter | |
| Last |
Instances
| Enum Channel # | |
Defined in Sound.ALSA.Mixer.Internal | |
| Eq Channel # | |
| Read Channel # | |
Defined in Sound.ALSA.Mixer.Internal | |
| Show Channel # | |
data PerChannel e #
PerChannel represents a capability that with either a separate value for
each channel or with a common value for all channels.
Constructors
| Joined | |
Fields
| |
| PerChannel | |
Fields
| |
Volume represents a volume capability. There may be a separate value per
channel, but each capability has only one range.
Constructors
| Volume | |
Fields
| |
type Switch = PerChannel Bool #
Switch represents a switch capability for controls and channels that can
be muted and unmuted.
Instances
Instances
Functions
Mixers
withMixer :: String -> (Mixer -> IO a) -> IO a #
Perform an IO action with the named mixer. An exception of type
T will be thrown if the named mixer cannot be
found. A mixer named "default" should always exist.
Controls
common :: Either a (Maybe a, Maybe a) -> Maybe a #
For a given capability, which may be for either playback or capture, or common to both, return the common capability if it exists.
playback :: Either a (Maybe a, Maybe a) -> Maybe a #
For a given capability, which may be for either playback or capture, or common to both, return the playback capability if it exists.
capture :: Either a (Maybe a, Maybe a) -> Maybe a #
For a given capability, which may be for either playback or capture, or common to both, return the capture capability if it exists.
PerChannels
channels :: PerChannel e -> [Channel] #
All channels supported by a PerChannel object.
allChannels :: [Channel] #
joined :: PerChannel e -> Bool #
True if the PerChannel object has a common value for all channels.
perChannel :: PerChannel e -> Bool #
True if the PerChannel object has a separate value for each channel.
getChannel :: Channel -> PerChannel x -> IO (Maybe x) #
Get the value associated with a particular channel, if that channel exists.
setChannel :: Channel -> PerChannel x -> x -> IO () #
Set the value associated with a particular channel, if that channel exists.
Examples
Getting and setting the volume of a Control
This example demonstrates the method of accessing the volume of a Control. The example function reads the volume and increases it by the value supplied.
changeVolumeBy :: CLong -> IO ()
changeVolumeBy i =
withMixer "default" $ \mixer ->
do Just control <- getControlByName mixer "Master"
let Just playbackVolume = playback $ volume control
(min, max) <- getRange playbackVolume
Just vol <- getChannel FrontLeft $ value $ playbackVolume
when ((i > 0 && vol < max) || (i < 0 && vol > min))
$ setChannel FrontLeft (value $ playbackVolume) $ vol + iGetting and setting the switch of a Control
This example demonstrates the method of accessing the switch of a Control. The example function reads the value of the switch and toggles it.
toggleMute :: IO ()
toggleMute =
withMixer "default" $ \mixer ->
do Just control <- getControlByName mixer "Master"
let Just playbackSwitch = playback $ switch control
Just sw <- getChannel FrontLeft playbackSwitch
setChannel FrontLeft playbackSwitch $ not sw