TECHNICAL SPECS

Polyglot Payload Extraction Mechanics

Name & Tag Fix uses a hybrid Batch/PowerShell polyglot structure[cite: 1, 2]. When executed, Windows CMD processes the batch header and calls PowerShell to extract the embedded script below the <#START_PS#> marker[cite: 1]:

powershell -NoProfile -Command "(Get-Content -LiteralPath '%~f0' -Raw) -split '<#START_PS#>\r?\n' | Select-Object -Last 1 | Set-Content -LiteralPath '%TempPS1%' -Encoding UTF8"

This allows drag-and-drop support on Windows without requiring users to unblock or run standalone .ps1 script files[cite: 1, 2].

FFprobe Stream Inspection & Selective Codec Skipping

To safely inspect containers and detect audio codecs without parsing errors, the script queries FFprobe in JSON mode[cite: 1]:

$probeJsonRaw = & $ffprobePath -v quiet -show_format -show_streams -print_format json $filePath | Out-String

The script parses both format-level and stream-level metadata blocks, inspecting codec_name to safely skip ALAC .m4a files (preventing FFmpeg MP4 atom stripping) while allowing AAC .m4a files through:

if ($ext -eq '.m4a' -and $codecName -eq 'alac') {
    Write-Host "[SKIP] ALAC .m4a skipped (FFmpeg strips MP4 atoms): $fileName" -ForegroundColor Yellow
    return
}

APEv2 Truncation & ReplayGain Scrubbing

Legacy tagging applications (dBpoweramp, LAME, MP3Gain) frequently attach binary APEv2 footers at the end of MP3 files. Because FFmpeg's stream copy passes trailing binary footers through untouched, Name & Tag Fix natively inspects and truncates APEv2 footers via binary stream seeking prior to FFmpeg processing:

function Strip-ApeTag($file) {
    $fs = [System.IO.File]::Open($file, [System.IO.FileMode]::Open, [System.IO.FileAccess]::ReadWrite, [System.IO.FileShare]::None)
    if ($fs.Length -gt 32) {
        $fs.Seek(-32, [System.IO.SeekOrigin]::End)
        # Checks for 'APETAGEX' header and truncates footer by tag size
        if ($header -eq "APETAGEX") { $fs.SetLength($fs.Length - $tagSize) }
    }
    $fs.Close()
}

Furthermore, all gain-related tags (including replaygain_*, playgain_*, and rg_*) are dynamically filtered out using regular expressions:

if ($key -match 'gain') { continue }

Metadata Normalization Matrix & Base FFmpeg Arguments

Name & Tag Fix normalizes inconsistent tag keys across formats into clean standard metadata[cite: 1]:

Base FFmpeg Flag Execution Engine

$ffmpegArgs = @(
    "-y", "-v", "error", "-i", $filePath, "-c", "copy", "-map", "0:a", 
    "-map_metadata", "-1", "-map_metadata:s:a", "-1", "-fflags", "+bitexact"
)

# Zeroes out container & stream metadata explicitly
$tagsToZeroOut = @('encoder', 'creation_time', 'handler_name', 'vendor_id', 'major_brand', 'minor_version')
foreach ($tZero in $tagsToZeroOut) {
    $ffmpegArgs += "-metadata", "${tZero}="
    $ffmpegArgs += "-metadata:s:a", "${tZero}="
}

• -map_metadata -1 & -map_metadata:s:a -1: Completely wipes global and stream-level container headers[cite: 1].
• -fflags +bitexact: Suppresses writing build timestamp signatures into output files[cite: 1].
• -map 0:v?: Preserves attached cover art streams for non-Opus containers[cite: 1].
• -id3v2_version 3: Enforces ID3v2.3 tag writing for MP3 compatibility[cite: 1].

Collision-Free GUID Processing

To support parallel processing and eliminate race conditions during file renaming, temporary files are tagged with an 8-character unique GUID string[cite: 1]:

$randStr = [guid]::NewGuid().ToString().Substring(0,8)
$tempFile = Join-Path $dir "temp_stripped_${randStr}_$fileName"

Once FFmpeg completes processing, the original file is safely replaced and atomically updated to the target filename[cite: 1].