SplitBy-Chapters.ps1

# PowerShell script to split MKV file by chapters using ffmpeg and ffprobe

param(
    [string]$InputFile,
    [string]$OutputPrefix = "Chapter"
)

# Get chapter information from the file in JSON format
# ffprobe extracts metadata; we're specifically requesting chapter information
$chapterJson = ffprobe -v quiet -print_format json -show_chapters $InputFile | ConvertFrom-Json

# Check if chapters were found
if ($null -eq $chapterJson.chapters -or $chapterJson.chapters.Count -eq 0) {
    Write-Host "No chapters found in the file!"
    exit
}

Write-Host "Found $($chapterJson.chapters.Count) chapters. Starting extraction..."

$chapterNum = 1

# Loop through each chapter
foreach ($chapter in $chapterJson.chapters) {
    
    # Format chapter number with leading zeros (e.g., 01, 02, 03)
    $chapterNumFormatted = "{0:D2}" -f $chapterNum
    
    # Get start and end times for this chapter
    $startTime = $chapter.start_time
    $endTime = $chapter.end_time
    
    # Create output filename
    $outputFile = "$($OutputPrefix)_$($chapterNumFormatted).mkv"
    
    # Display progress
    Write-Host "Extracting Chapter $chapterNum ($startTime to $endTime) -> $outputFile"
    
    # Run ffmpeg to extract this chapter
    # -i: input file
    # -c copy: copy streams without re-encoding (fast!)
    # -ss: start time
    # -to: end time

    ffmpeg -i $InputFile -c copy -ss $startTime -to $endTime $outputFile

    $chapterNum += 1
}

Write-Host "Done! Extracted $($chapterJson.chapters.Count) chapters."