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我正在尝试使用 hsndfile（libsndfile 的 Haskell 绑定）来生成一个 .wav 文件，但我又遇到了一个无法克服的难题。以下代码引发错误“格式错误”。（如 openWavHandle 中所写）。我已经尝试了我认为存在的所有字节顺序与 HeaderFormatWav 和 SampleFormatPcm16 的组合，但无济于事。有谁知道如何解决这一问题？

import qualified Sound.File.Sndfile as Snd
import qualified Graphics.UI.SDL.Mixer.Channels as SDLC
import qualified Graphics.UI.SDL.Mixer.General as SDLG
import qualified Graphics.UI.SDL.Mixer.Samples as SDLS

import Control.Applicative
import Foreign.Marshal.Array
import Data.List.Split (splitOn)
import Data.Word (Word16)
import System.IO (hGetContents, Handle, openFile, IOMode(..))

a4 :: Double
a4 = 440.0

frameRate :: Int
frameRate = 16000

noteLength :: Double
noteLength = 5.0

volume = maxBound `div` 2 :: Word16

noteToFreq :: (String, Int) -> Double
noteToFreq (note, octave) =
    if octave >= -1 && octave < 10 && n /= 12.0
    then a4 * 2 ** ((o - 4.0) + ((n - 9.0) / 12.0))
    else undefined
    where o = fromIntegral octave :: Double
          n = case note of
                "B#" -> 0.0
                "C"  -> 0.0
                "C#" -> 1.0
                "Db" -> 1.0
                "D"  -> 2.0
                "D#" -> 3.0
                "Eb" -> 3.0
                "E"  -> 4.0
                "Fb" -> 4.0
                "E#" -> 5.0
                "F"  -> 5.0
                "F#" -> 6.0
                "Gb" -> 6.0
                "G"  -> 7.0
                "G#" -> 8.0
                "Ab" -> 8.0
                "A"  -> 9.0
                "A#" -> 10.0
                "Bb" -> 10.0
                "B"  -> 11.0
                "Cb" -> 11.0
                _    -> 12.0

notesToFreqs :: [(String, Int)] -> [Double]
notesToFreqs = map noteToFreq 

noteToSample :: Double -> [Word16]
noteToSample freq =
    take (round $ noteLength * fromIntegral frameRate) $
    map ((round . (* fromIntegral volume)) . sin) 
    [0.0, (freq * 2 * pi / fromIntegral frameRate)..]

notesToSamples :: [Double] -> [Word16]
notesToSamples = concatMap noteToSample 

getFileName :: IO FilePath
getFileName = putStr "Enter the name of the file: " >> getLine

openMFile :: FilePath -> IO Handle
openMFile fileName = openFile fileName ReadMode

getNotesAndOctaves :: IO String
getNotesAndOctaves = getFileName >>= openMFile >>= hGetContents 

noteValuePairs :: String -> [(String, Int)]
noteValuePairs = pair . splitOn " "
    where pair (x:y:ys) = (x, read y) : pair ys
          pair []       = []

getWavSamples :: IO [Word16]
getWavSamples = (notesToSamples . notesToFreqs . noteValuePairs) <$>
                getNotesAndOctaves 

extendNotes :: [Word16] -> [Word16]
extendNotes = concatMap (replicate 1000)

format :: Snd.Format
format = Snd.Format Snd.HeaderFormatWav Snd.SampleFormatPcm16 Snd.EndianBig

openWavHandle :: [Word16] -> IO Snd.Handle
openWavHandle frames =
    let info = Snd.Info (length frames) frameRate 1 format 1 False
    in if Snd.checkFormat info
       then Snd.openFile "temp.wav" Snd.WriteMode info
       else error "Bad format."

writeWav :: [Word16] -> IO Snd.Count
writeWav frames = openWavHandle frames >>= \h ->
                  newArray frames >>= \ptr ->
                  Snd.hPutBuf h ptr (length frames) >>= \c ->
                  return c

makeWavFile :: IO ()
makeWavFile = getWavSamples >>= \s ->
              writeWav s >>= \c ->
              putStrLn $ "Frames written: " ++ show c
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2 回答 2

1

安德鲁，

我是 libsndfile 的主要作者，也是一个 Haskell 黑客。我已经看过了，就我而言，下面的最小示例代码应该可以工作。

import qualified Sound.File.Sndfile as Snd
import Control.Applicative
import Foreign.Marshal.Array
import Data.Word (Word16)
import System.IO (hGetContents, Handle, openFile, IOMode(..))

format :: Snd.Format
format = Snd.Format Snd.HeaderFormatWav Snd.SampleFormatPcm16 Snd.EndianFile

openWavHandle :: [Word16] -> IO Snd.Handle
openWavHandle frames =
    let info = Snd.Info (length frames) 441000 1 format 1 False
    in Snd.openFile "temp.wav" Snd.WriteMode info

writeWav :: [Word16] -> IO Snd.Count
writeWav frames = openWavHandle frames >>= \h ->
              newArray frames >>= \ptr ->
              Snd.hPutBuf h ptr (length frames) >>= \c ->
              return c

makeWavFile :: IO ()
makeWavFile = writeWav [1..256] >>= \c ->
          putStrLn $ "Frames written: " ++ show c


main :: IO ()
main = makeWavFile

事实上它并没有暗示 hsndfile 中有问题。为了证明这一点，我将 C 源代码破解到 libsndfile 以打印出 SF_INFO 结构（hsndfile 调用 Info）的值，然后执行以下操作：

samplerate : 1
channels   : 65538
format     : 0x1

这显然是错误的。

我看过 hsndfile 的 Interface.hsc 代码。格式字段的值实际上以通道字段结束，通道字段以采样率字段结束。

我弄乱了这段代码，但我没有得到任何地方。我将 ping 上游 hsndfile 维护者。

于 2011-05-07T05:30:58.590 回答
1

感谢 Erik，这个错误在 Hackage 的 0.5.1 版本中得到修复。

由于 Linux 上缺少包含sndfile.h，Haskell 绑定生成器无法确定样本计数的大小sf_count_t应该是 64 位，因此Info当转换为 C 表示时结构会出现乱码。

请将有关此问题的后续行动直接发送到hsndfile 跟踪器。

于 2011-05-11T09:43:30.633 回答