Overview

ProteaAudio-SDL is a stereo audio mixer/playback library for SDL (platform independent).

Supported audio formats:

• Wav
• Ogg
• Mp3
• Raw linear PCM

Samples can be loaded from file or memory.

Setup

On Linux you need to install the SDL2 library:

sudo apt install libsdl2-dev

Build

Stack

stack setup
stack build

Nix:

stack --nix build

Example

import Control.Monad
import System.Environment
import System.FilePath
import qualified Data.ByteString as SB
import Control.Concurrent

import Sound.ProteaAudio.SDL

waitPlayback = do
  n <- soundActiveAll
  when  (n > 0) $ do
    threadDelay oneSec
    waitPlayback

oneSec :: Int
oneSec = 1000000 -- micro seconds

main = do
  args <- getArgs
  filename <- case args of
    a : _ -> pure a
    _ -> fail "usage: proteaaudio-play SAMPLE_FILE_NAME"

  result <- initAudio 64 44100 1024 -- max channels, mixing frequency, mixing buffer size
  unless result $ fail "failed to initialize the audio system"

  -- (A) load sample from file
  sampleA <- sampleFromFile filename 1.0 -- volume

  -- start two sound tracks with shared sample data
  sndTrkA <- soundPlay sampleA 1 1 0 1 -- left volume, right volume, time difference between left and right, pitch factor for playback
  threadDelay oneSec -- wait 1 sec
  sndTrkB <- soundPlay sampleA 1 1 0 1 -- left volume, right volume, time difference between left and right, pitch factor for playback
  soundActive sndTrkB >>= print
  -- play 3 sec
  threadDelay $ 3 * oneSec
  soundStop sndTrkB
  soundActive sndTrkB >>= print

  soundUpdate sndTrkA True 1 1 0 1
  putStrLn "pause sound, press enter to continue"
  getLine
  soundUpdate sndTrkA False 1 1 0 1

  -- wait sndTrkA to finish
  waitPlayback

  -- (B) load from memory buffer
  buffer <- SB.readFile filename
  sampleB <- case takeExtension filename of
    ".ogg" -> sampleFromMemoryOgg buffer 1.0
    ".wav" -> sampleFromMemoryWav buffer 1.0
    ".mp3" -> sampleFromMemoryMp3 buffer 1.0

  soundPlay sampleB 1 1 0 1 -- left volume, right volume, time difference between left and right, pitch factor for playback
  waitPlayback

  sampleDestroy sampleB
  soundPlay sampleB 1 1 0 1 -- we have invalidated the handle; nothing should happen now
  waitPlayback

  finishAudio