Question

我正在编写一个在Linux，Windows和OS X上运行的Haskell命令行应用程序。我现在必须从中播放音频文件（.wav，.ogg和.mp3）。我将如何实现一个功能

playAudioFile :: FilePath -> IO ()

甚至更好

playAudio :: ByteString -> IO ()

只适用于所有系统？

（我很高兴调用常见的命令行工具，也不介意将它们捆绑为Windows发行版。）

Answer 1

这是我提出的代码，使用SDL-1.2：

module PlaySound (withSound, playSound) where

import Control.Monad
import System.IO
import System.Directory
import Data.Foldable
import Control.Exception
import qualified Data.ByteString.Lazy as B
import Foreign.ForeignPtr

import Graphics.UI.SDL as SDL
import Graphics.UI.SDL.Mixer as Mix

withSound :: IO a -> IO a
withSound = bracket_ init cleanup
  where
    init = do
        SDL.init [SDL.InitAudio]
        getError >>= traverse_ putStrLn
        ok <- Mix.tryOpenAudio Mix.defaultFrequency Mix.AudioS16LSB 2  4096
        unless ok $
            putStrLn "Failed to open SDL audio device"

    cleanup = do
        Mix.closeAudio
        SDL.quit

playSound :: B.ByteString -> IO ()
playSound content = do
        dir <- getTemporaryDirectory
        (tmp, h) <- openTempFile dir "sdl-input"
        B.hPutStr h content
        hClose h

        mus <- Mix.loadMUS tmp
        Mix.playMusic mus 1
        wait

        -- This would double-free the Music, as it is also freed via a
        -- finalizer
        --Mix.freeMusic mus
        finalizeForeignPtr mus
        removeFile tmp

wait :: IO ()
wait = do
    SDL.delay 50
    stillPlaying <- Mix.playingMusic
    when stillPlaying wait

该程序最终工作正常，但

在Windows下编译SDL绑定很棘手。我跟着this nice explanation on how to do it
SDL-1.2的SDL绑定似乎没有维护，do not even compile with GHC-7.8 or newer。起初我没有注意到，因为我的发行版（Debian）修补了这些问题，但这意味着我的用户不能轻易地cabal install依赖项。
SDL-2有绑定，但SDL_mixer没有绑定，我需要（我相信）。

所以我很乐意阅读更好的答案。

如何从跨平台的Haskell代码播放音频文件

1 个答案: