two pass audio normalise ffmpeg powershell

normaliseVideo.ps1

# --- Configuration ---
$inputFile  = "C:\Users\new\Videos\someVideo.mp4"
$outputFile = "C:\Users\new\Videos\someVideoNormalised.mp4"

# --- Target Loudness ---
$target_I   = "-14"
$target_LRA = "7"
$target_TP  = "-1.5"

Write-Host "Running Pass 1 (analysis)..." -ForegroundColor Yellow

# Build filter safely (join with ':')
$filter1 = @(
    "loudnorm=I=$target_I"
    "LRA=$target_LRA"
    "TP=$target_TP"
    "print_format=json"
) -join ':'

# Run ffmpeg pass 1 (use call operator '&' with argument tokens)
$ffmpegOutput = & ffmpeg -hide_banner -i $inputFile -af $filter1 -f null NUL 2>&1

# Extract JSON block
$jsonMatch = [regex]::Match($ffmpegOutput, '(?s)\{.*\}')
if (-not $jsonMatch.Success) {
    Write-Host $ffmpegOutput
    throw "No JSON stats found."
}

# Parse JSON
$stats = $jsonMatch.Value | ConvertFrom-Json
Write-Host ("Measured I  : {0}" -f $stats.input_i)
Write-Host ("Measured TP : {0}" -f $stats.input_tp)
Write-Host ("Measured LRA: {0}" -f $stats.input_lra)

Write-Host "Running Pass 2 (normalising)..." -ForegroundColor Yellow

# Build second-pass filter safely (no concatenation-before-colon issues)
$filter2 = @(
    "loudnorm=I=$target_I"
    "LRA=$target_LRA"
    "TP=$target_TP"
    ("measured_I={0}" -f $stats.input_i)
    ("measured_TP={0}" -f $stats.input_tp)
    ("measured_LRA={0}" -f $stats.input_lra)
    ("measured_thresh={0}" -f $stats.input_thresh)
    ("offset={0}" -f $stats.target_offset)
) -join ':'

# Run ffmpeg pass 2
& ffmpeg -hide_banner -i $inputFile -af $filter2 -c:v copy -c:a aac -y $outputFile
if ($LASTEXITCODE -ne 0) {
    throw "FFmpeg Pass 2 failed."
}

Write-Host "Done. Normalised file saved to: $outputFile" -ForegroundColor Green