如果你是一名音樂發(fā)燒友，那么應該知道Flac這種常見的無損音樂格式。Flac音樂文件支持metadata，用戶可以編輯metadata，讓音樂文件帶有藝術家、所屬專輯、音軌等等信息。

通常來說，metadata和音頻數(shù)據(jù)并不相關，修改metadata并不會影響音頻本身。

但是，近日微軟官方公布了Win10中存在一個Bug，在Win10中用資源管理器修改Flac文件的metadata，竟會導致音頻的損壞!

根據(jù)Windows Latest的報道，微軟最新發(fā)布的一份支持文件披露，如果在Win10的2004或者更高版本中，使用文件資源管理器修改Flac音樂文件的metadata，就會損耗Flac音頻文件。

這個Bug在Win10專業(yè)版、家庭版、企業(yè)版、工作站版乃至其他版本的Win10中均有出現(xiàn)。

根據(jù)微軟本月早些時候發(fā)布的支持文件，Win10的文件資源管理器導致了這個錯誤，它破壞了Flac文件頭包含的ID3框架也就是metadata，而這個ID3框架負責存儲音頻的注釋，例如音樂標題、藝術家、專輯、曲目編號等。

在Win10上，F(xiàn)lac的處理程序忽視了ID3框架，該程序認為Flac文件在使用4字節(jié)的文件頭，當Flac文件被Win10編輯的時候，ID3框架被覆蓋了，導致沒有了開始代碼，導致了音樂播放器無法識別被修改后的文件。

因此，在Win10中，如果你直接用文件資源管理器修改Flac音樂文件的標題、藝術家等metadata，會導致該文件無法播放。

幸運的是，微軟已經確定了Bug的根本原因，用戶可以通過Windows Update升級KB5003214補丁進行修復。

在KB5003214補丁中，微軟確認了上文提到的錯誤已經被修復，修改了Flac的標題、藝術家等metadata后，F(xiàn)lac不會再變得無法播放。

而對于已經損壞了的Flac文件，微軟則發(fā)布了一個PowerShell腳本來進行修復，運行該腳本后Flac文件即可重新播放，不過已經從ID3框架中丟失了的metadata信息并不能恢復。

下面是利用PowerShell腳本修復Flac文件的具體方法。

1、開啟記事本;

2、復制以下字符，粘貼到記事本中：

# Copyright 2021 Microsoft

# This script will repair a FLAC file that has been corrupted by Media Foundation in reference to KB5003430.

# Refer to KB5003430 for further information

param(

[parameter(Mandatory=$true,

HelpMessage="The path to the FLAC file that has been corrupted by Media Foundation",

ValueFromRemainingArguments=$true)]

[ValidateScript({ -not [String]::IsNullOrEmpty($_) -and (Test-Path $_) })]

[String]$File

)

# We need to back up the current file incase we have any errors

$FileDirectory = Split-Path -Resolve $File

$Filename = Split-Path -Leaf -Resolve $File

$FullPath = Join-Path -Resolve $FileDirectory $Filename

$Filename = [String]::Format("Backup_{0:yyyyMMdd_hhmmss}_{1}", [DateTime]::Now, $Filename)

$BackupLocation = Join-Path $FileDirectory $Filename

Write-Output "Microsoft FLAC Repair Tool. This tool will repair a FLAC audio file that was corrupted when editing its details."

Write-Output "Affected File: $FullPath"

Write-Output "A backup of the file will be made: $BackupLocation"

Write-Output "Do you wish to continue?"

$choice=$host.ui.PromptForChoice("Fixing FLAC Script", "Do you wish to continue", ('&Yes', '&No'), 1)

function ParseStreamInfoMetadataBlock([System.IO.FileStream]$stream)

{

$blockType = $stream.ReadByte()

$lastBlock = ($blockType -shr 7) -ne 0

$blockType = $blockType -band 0x7F

if ($blockType -ne 0)

{

return $false

}

$blockSize = (($stream.ReadByte() -shl 16) -bor ($stream.ReadByte() -shl 8) -bor $stream.ReadByte())

if ($blockSize -lt 34)

{

return $false

}

$minAudioBlockSize = ($stream.ReadByte() -shl 8) -bor $stream.ReadByte()

$maxAudioBlockSize = ($stream.ReadByte() -shl 8) -bor $stream.ReadByte()

if ($minAudioBlockSize -lt 16 -or $maxAudioBlockSize -lt 16)

{

return $false

}

$minFrameSize = (($stream.ReadByte() -shl 16) -bor ($stream.ReadByte() -shl 8) -bor $stream.ReadByte())

$maxFrameSize = (($stream.ReadByte() -shl 16) -bor ($stream.ReadByte() -shl 8) -bor $stream.ReadByte())

$sampleInfo = (($stream.ReadByte() -shl 24) -bor ($stream.ReadByte() -shl 16) -bor ($stream.ReadByte() -shl 8) -bor $stream.ReadByte())

$sampleRate = $sampleInfo -shr 12

$channelCount = (($sampleInfo -shr 9) -band 0x7) + 1

$bitsPerSample = (($sampleInfo -shr 4) -band 0x1F) + 1

[UInt64]$sampleCount = (($stream.ReadByte() -shl 24) -bor ($stream.ReadByte() -shl 16) -bor ($stream.ReadByte() -shl 8) -bor $stream.ReadByte())

$sampleCount = (([UInt64]$sampleInfo -band 0xF) -shl 32) -bor $sampleCount

$MD5HashBytes = New-Object byte[] 16

$stream.Read($MD5HashBytes, 0, $MD5HashBytes.Length)

$MD5Hash = [Guid]($MD5HashBytes)

if ($sampleRate -eq 0)

{

return $false

}

# Passing these checks means that we likely have a stream info header and can rebuild the file

Write-Output "File Stream Information"

Write-Output "Sample Rate: $sampleRate"

Write-Output "Audio Channels: $channelCount"

Write-Output "Sample Depth: $bitsPerSample"

Write-Output "MD5 Audio Sample Hash: $MD5Hash"

return $true

}

if ($choice -eq 0)

{

Copy-Item $FullPath -Destination $BackupLocation -Force

$stream = [System.IO.File]::Open($FullPath, [System.IO.FileMode]::Open)

$stream.Seek(4, [System.IO.SeekOrigin]::Begin)

while ($stream.ReadByte() -eq 0) {}

# We now need to figure out where a valid FLAC metadata frame begins

# We are likely pointing to the last byte of the size member so we'll seek back 4 bytes and retry

$flacDataStartPosition = $stream.Position - 4

$stream.Seek($flacDataStartPosition, [System.IO.SeekOrigin]::Begin)

while (-not(ParseStreamInfoMetadataBlock($stream)))

{

$flacDataStartPosition = $flacDataStartPosition + 1

$stream.Seek($flacDataStartPosition, [System.IO.SeekOrigin]::Begin)

}

# Insert the start code

$stream.Seek($flacDataStartPosition, [System.IO.SeekOrigin]::Begin)

if (Test-Path "$FullPath.tmp")

{

Remove-Item "$FullPath.tmp"

}

$fixedStream = [System.IO.File]::Open("$FullPath.tmp", [System.IO.FileMode]::CreateNew)

[byte[]]$startCode = [char[]]('f', 'L', 'a', 'C');

$fixedStream.Write($startCode, 0, $startCode.Length)

$stream.CopyTo($fixedStream)

$stream.Close()

$fixedStream.Close()

Move-Item -Force "$FullPath.tmp" $FullPath

}

3、保存文件，在“另存為”對話框中，將目錄定位到你想要保存PowerShell腳本的位置;

4、在文件名輸入框中，輸入“FixFlacFiles.ps1”，將另存為文件的類型更改為Text Documents (*.txt);

5、進入到你保存該PowerShell腳本的目錄;

6、右鍵點擊剛剛保存的腳本，然后選擇“使用PowerShell運行”;

7、出現(xiàn)提示時，輸入無法播放的Flac文件的文件名，然后按下回車鍵。

微軟建議大家安裝本月推送的可選累積更新，以避免修改Flac文件metadata出現(xiàn)的問題。