如何从跨平台的Haskell代码播放音频文件

问题描述

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

I’m writing a Haskell command line application that runs on Linux, Windows and OS X. I now have to play audio files (.wav, .ogg and .mp3) from it. How would I go about implementing a function

playAudioFile :: FilePath -> IO ()

甚至更好

playAudio :: ByteString -> IO ()

在所有系统上都能正常工作吗?

that simply works on all system?

(我很高兴调用常见的命令行工具，并且不介意将它们捆绑到Windows发行版中.)

(I’m happy to invoke common command line tools and also don’t mind bundling them for the Windows distribution.)

推荐答案

这是我使用SDL-1.2想到的代码:

This is the code I came up with, using 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

该程序最终运行良好，但是

The program in the end works fine, but

• 在Windows下编译SDL绑定非常棘手.我遵循了关于此操作的很好的解释
• 似乎未维护SDL-1.2的SDL绑定，并且不会甚至可以使用GHC-7.8或更高版本进行编译.起初我没有注意到，因为我的发行版(Debian)围绕此类问题进行了修补，但这意味着我的用户不再容易cabal install依赖项.
• 有SDL-2的绑定，但没有SDL_mixer的绑定，我在这里需要(我相信).

• compiling the SDL bindings under Windows is tricky. I followed this nice explanation on how to do it
• the SDL bindings for SDL-1.2 seem to be unmaintained and do not even compile with GHC-7.8 or newer. I didn’t notice at first, because my distribution (Debian) patches around such issues, but it means that my users cannot easily cabal install the dependencies any more.
• there are bindings for SDL-2, but none for the SDL_mixer, which I need here (I believe).

所以我会很高兴阅读更好的答案.

So I’ll happily read better answers.

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