Batch Convert WAV to AAC with PowerShell and FFmpeg

Converting multiple uncompressed WAV audio files into high-efficiency AAC files on Windows can save significant disk space while maintaining high audio quality. This guide provides a ready-to-run PowerShell script that utilizes FFmpeg to automatically scan a directory, convert every WAV file to an AAC format, and output the encoded files cleanly to a specified folder.

Prerequisites

Before running the script, ensure you have FFmpeg installed on your system. You can verify this by opening a PowerShell prompt and running:

ffmpeg -version

If the command is not recognized, download FFmpeg, extract it, and add its bin folder to your Windows system's Environment Variables (PATH).

The Batch Conversion Script

Open a text editor (such as Notepad or VS Code), paste the following script, and modify the $sourceDir and $targetDir paths to match your folder locations:

# Define source and destination directories
$sourceDir = "C:\Audio\WAV_Files"
$targetDir = "C:\Audio\AAC_Files"
$bitrate   = "192k"

# Create target directory if it does not exist
if (-not (Test-Path -Path $targetDir)) {
    New-Item -ItemType Directory -Path $targetDir -Force | Out-Null
}

# Fetch all WAV files in the source directory
$wavFiles = Get-ChildItem -Path $sourceDir -Filter *.wav -File

if ($wavFiles.Count -eq 0) {
    Write-Host "No WAV files found in $sourceDir" -ForegroundColor Yellow
    exit
}

# Loop through each WAV file and convert to AAC
foreach ($file in $wavFiles) {
    $outputPath = Join-Path -Path $targetDir -ChildPath "$($file.BaseName).m4a"

    Write-Host "Converting: $($file.Name) -> $($file.BaseName).m4a" -ForegroundColor Cyan

    # Run FFmpeg conversion
    & ffmpeg -hide_banner -loglevel error -stats -i $file.FullName -c:a aac -b:a $bitrate -y $outputPath
}

Write-Host "Batch conversion completed successfully." -ForegroundColor Green

Script Breakdown

  • Get-ChildItem -Filter *.wav -File: Scans the source folder specifically for files ending with .wav. To include subdirectories recursively, add the -Recurse flag.
  • $file.BaseName: Extracts the file name without the .wav extension, allowing the script to append the appropriate container extension.
  • .m4a Extension: AAC streams are typically wrapped in an MP4/M4A container for maximum player compatibility on Windows and macOS. If you require raw ADTS AAC streams, change the extension to .aac.
  • -c:a aac: Specifies the native FFmpeg AAC audio encoder.
  • -b:a 192k: Sets the target audio bitrate to 192 kbps. You can adjust this value (e.g., 128k, 256k, or 320k) based on your quality requirements.
  • -hide_banner -loglevel error -stats: Suppresses unnecessary FFmpeg licensing information and limits the output to errors and progress updates.
  • -y: Overwrites output files automatically if they already exist.

How to Run the Script

  1. Save the file with a .ps1 extension, such as convert-wav-to-aac.ps1.

  2. Open PowerShell and navigate to the directory where the script is saved.

  3. If running scripts is restricted on your system, allow execution for the current session by running:

    Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass

  4. Execute the script:

    .\convert-wav-to-aac.ps1