269 lines
12 KiB
PowerShell
269 lines
12 KiB
PowerShell
<#
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.SYNOPSIS
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Detects scenes in a video file with ffmpeg and extracts each scene as a separate video clip file.
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.DESCRIPTION
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Analyzes the input video with ffmpeg scene-change detection, using the -Scene threshold, and computes
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the first and last frame (0-based) of each detected scene. Each scene is then extracted by calling
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Create-Clip.ps1 (located in the same directory as this script) with the scene frame range, which in
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turn calls Clone-Video.ps1.
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Clip files are always saved in the same directory as the input video. The clip filename is the input
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video filename plus the scene suffix, with the scene number starting at 1
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(ex: P01.mp4 scene 1 becomes P01-Scene-01.mp4). For sources carrying a .skip marker, the marker stays
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last, as handled by Create-Clip.ps1 (ex: P01.skip.mp4 becomes P01-Scene-01.skip.mp4).
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Encoding is performed by Clone-Video.ps1: by default each clip keeps the resolution, frame rate and
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compression characteristics of the input video, unless overridden with extra parameters (ex: -Size,
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-FPS, -CRF) forwarded to Create-Clip.ps1.
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The list of scenes (index, start frame, end frame, frame count, start time, end time) is always displayed.
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If no scene change is detected, the whole video is treated as a single scene.
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Unless -List is specified, existing scene clip files from a previous run (same directory, same source
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name, same suffix pattern and same extension) are deleted before the new clips are created. Existing
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files are always replaced.
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Scene detection and the scene list are read-only: they always run, including with -List and -WhatIf.
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Only the deletion and the creation of files are subject to -WhatIf and -Confirm. Both switches are
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also forwarded to Create-Clip.ps1.
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.PARAMETER Video
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Path to the input video file. Can be absolute or relative to current directory. If the path has no
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extension, .mp4, .webm and .mkv are tried in turn.
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.PARAMETER Scene
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Threshold value between 0 and 1.0 to determine scene changes. Lower values mean more sensitive
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detection (more scenes). Default is 0.3.
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.PARAMETER Suffix
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Scene suffix to use for the output video clip files. Must contain a printf-style number placeholder
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such as %02d, which is replaced by the scene number starting at 1. By default, "-Scene-%02d" is used.
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.PARAMETER List
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Only displays the list of scenes. No video clip file is created and no existing file is deleted.
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.PARAMETER ExtraArgs
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Additional parameters passed as-is to Create-Clip.ps1 and from there to Clone-Video.ps1
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(ex: -Size 720p -NoAudio -CRF 18 -LTX). The parameters -Video, -Frames, -Suffix and -Target are
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managed by this script and must not be repeated.
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.EXAMPLE
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.\Create-Scenes.ps1 -Video P01.mp4 -Scene 0.4 -List
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Lists the scenes detected in P01.mp4 without creating or deleting any file.
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.EXAMPLE
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.\Create-Scenes.ps1 -Video P01 -Scene 0.3 -Size 720p -NoAudio
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Creates P01-Scene-01.mp4, P01-Scene-02.mp4, ... scaled to 720p and without audio.
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.EXAMPLE
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.\Create-Scenes.ps1 -Video P01.mp4 -Suffix "-Shot-%03d" -WhatIf
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Shows which files would be deleted and created, without changing anything.
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#>
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[CmdletBinding(SupportsShouldProcess, ConfirmImpact = 'Medium')]
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param(
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[Parameter(Mandatory = $true, Position = 0)]
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[ValidateNotNullOrEmpty()]
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[string]$Video,
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[Parameter(Mandatory = $false)]
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[ValidateRange(0.0, 1.0)]
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[double]$Scene = 0.3,
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[Parameter(Mandatory = $false)]
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[ValidateNotNullOrEmpty()]
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[ValidatePattern('%0?\d*d')]
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[string]$Suffix = '-Scene-%02d',
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[switch]$List,
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[Parameter(ValueFromRemainingArguments)]
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[object[]]$ExtraArgs
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)
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Set-StrictMode -Version Latest
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$ErrorActionPreference = 'Stop'
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$invariant = [Globalization.CultureInfo]::InvariantCulture
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function Resolve-VideoPath {
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param([string]$Path)
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$candidates = @($Path) + @('.mp4', '.webm', '.mkv' | ForEach-Object { "$Path$_" })
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$found = $candidates | Where-Object { Test-Path -LiteralPath $_ -PathType Leaf } | Select-Object -First 1
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if (-not $found) { throw "Video file not found: $Path" }
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(Resolve-Path -LiteralPath $found).Path
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}
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function ConvertTo-Number {
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param([string]$Text)
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# Parses plain numbers and ffprobe rationals (e.g. "30000/1001"). Returns $null for N/A or invalid values.
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$parts = $Text -split '/'
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$num = 0.0
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$den = 1.0
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if ($parts.Count -gt 2 -or -not [double]::TryParse($parts[0], [Globalization.NumberStyles]::Float, $invariant, [ref]$num)) { return $null }
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if ($parts.Count -eq 2 -and (-not [double]::TryParse($parts[1], [Globalization.NumberStyles]::Float, $invariant, [ref]$den) -or $den -eq 0)) { return $null }
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$num / $den
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}
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function Get-VideoInfo {
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param([string]$Path)
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$ffArgs = @('-hide_banner', '-v', 'error', '-count_frames', '-select_streams', 'v:0',
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'-show_entries', 'stream=avg_frame_rate,r_frame_rate,start_time,nb_read_frames,nb_frames,duration',
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'-of', 'default=noprint_wrappers=1', $Path)
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Write-Verbose ('ffprobe ' + ($ffArgs -join ' '))
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$lines = & ffprobe @ffArgs
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if ($LASTEXITCODE -ne 0) { throw "ffprobe failed to read $Path" }
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$fields = @{}
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foreach ($line in $lines) {
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if ("$line" -match '^(\w+)=(.*)$') { $fields[$Matches[1]] = $Matches[2] }
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}
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$fps = ConvertTo-Number $fields['avg_frame_rate']
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if (-not $fps) { $fps = ConvertTo-Number $fields['r_frame_rate'] }
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if (-not $fps) { throw "Cannot read the frame rate of $Path" }
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$startTime = ConvertTo-Number $fields['start_time']
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if ($null -eq $startTime) { $startTime = 0.0 }
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$frames = ConvertTo-Number $fields['nb_read_frames']
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if ($null -eq $frames) { $frames = ConvertTo-Number $fields['nb_frames'] }
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if ($null -eq $frames) { $frames = [Math]::Round((ConvertTo-Number $fields['duration']) * $fps) }
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if ($frames -lt 1) { throw "Cannot determine the frame count of $Path" }
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[pscustomobject]@{ Fps = $fps; StartTime = $startTime; TotalFrames = [int][Math]::Round($frames) }
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}
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function Get-SceneChangeTime {
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param([string]$Path, [double]$Threshold)
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$filter = "select='gt(scene,{0})',showinfo" -f $Threshold.ToString($invariant)
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$ffArgs = @('-hide_banner', '-nostats', '-loglevel', 'info', '-i', $Path, '-vf', $filter, '-an', '-f', 'null', '-')
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Write-Verbose ('ffmpeg ' + ($ffArgs -join ' '))
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$output = & ffmpeg @ffArgs 2>&1 | Out-String
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if ($LASTEXITCODE -ne 0) { throw "ffmpeg scene detection failed on $Path" }
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[regex]::Matches($output, 'pts_time:([\d.]+)') | ForEach-Object { [double]::Parse($_.Groups[1].Value, $invariant) }
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}
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function Format-SceneSuffix {
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param([string]$Template, [int]$Number)
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# Replaces only the first printf-style placeholder (%d, %2d, %02d, %003d) with the zero-padded number.
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$placeholder = [regex]::Match($Template, '%0*(\d*)d')
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$width = [Math]::Max(1, [int]('0' + $placeholder.Groups[1].Value))
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$Template.Substring(0, $placeholder.Index) + $Number.ToString('D' + $width, $invariant) +
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$Template.Substring($placeholder.Index + $placeholder.Length)
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}
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function Get-SceneList {
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param($Info, [double[]]$ChangeTimes, [string]$Template)
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# pts_time * fps is exact only for constant frame rate videos; with variable frame rate,
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# scene boundaries can be off by one frame.
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$boundaries = @($ChangeTimes | ForEach-Object { [int][Math]::Round(($_ - $Info.StartTime) * $Info.Fps) } |
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Where-Object { $_ -gt 0 -and $_ -lt $Info.TotalFrames } | Sort-Object -Unique)
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$starts = @(0) + $boundaries
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for ($i = 0; $i -lt $starts.Count; $i++) {
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$start = [int]$starts[$i]
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$end = if ($i + 1 -lt $starts.Count) { $starts[$i + 1] - 1 } else { $Info.TotalFrames - 1 }
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[pscustomobject]@{
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Index = $i + 1
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StartFrame = $start
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EndFrame = $end
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Frames = $end - $start + 1
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StartTime = [Math]::Round($start / $Info.Fps, 3)
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EndTime = [Math]::Round($end / $Info.Fps, 3)
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Suffix = Format-SceneSuffix -Template $Template -Number ($i + 1)
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}
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}
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}
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function Get-SceneFilePattern {
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param([string]$VideoPath, [string]$Template)
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# Regex matching the clip files this script creates for this source; used to find files of previous runs.
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$ext = [IO.Path]::GetExtension($VideoPath)
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$stem = [IO.Path]::GetFileNameWithoutExtension($VideoPath)
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$skipMarker = ''
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if ($stem -match '^(.*)(\.skip)$') {
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$stem = $Matches[1]
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$skipMarker = '\.skip'
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}
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$placeholder = [regex]::Match($Template, '%0*\d*d')
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$suffixPattern = [regex]::Escape($Template.Substring(0, $placeholder.Index)) + '\d+' +
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[regex]::Escape($Template.Substring($placeholder.Index + $placeholder.Length))
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'^' + [regex]::Escape($stem) + $suffixPattern + $skipMarker + [regex]::Escape($ext) + '$'
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}
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function Remove-ExistingScene {
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[CmdletBinding(SupportsShouldProcess)]
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param([string]$VideoPath, [string]$Pattern)
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$directory = [IO.Path]::GetDirectoryName($VideoPath)
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$existing = Get-ChildItem -LiteralPath $directory -File |
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Where-Object { $_.Name -match $Pattern -and $_.FullName -ne $VideoPath }
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foreach ($file in $existing) {
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if ($PSCmdlet.ShouldProcess($file.FullName, 'Delete existing scene file')) {
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Remove-Item -LiteralPath $file.FullName
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}
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}
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}
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function ConvertTo-ClipArgument {
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param([object[]]$Tokens)
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# Validates the extra arguments: every value must follow a parameter name, and parameter names without a value are switches.
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$params = @{}
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$pending = $null
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foreach ($token in $Tokens) {
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if ($token -is [string] -and $token -match '^-([A-Za-z]\w*)(:(.*))?$') {
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if ($pending) { $params[$pending] = $true }
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$pending = $Matches[1]
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if ($Matches[2]) {
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$params[$pending] = $Matches[3]
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$pending = $null
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}
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}
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elseif ($pending) {
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$params[$pending] = $token
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$pending = $null
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}
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else {
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throw "Unexpected argument '$token'. Extra parameters must be passed by name (e.g. -Size 720p)."
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}
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}
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if ($pending) { $params[$pending] = $true }
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$params
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}
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foreach ($tool in 'ffmpeg', 'ffprobe') {
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if (-not (Get-Command $tool -ErrorAction SilentlyContinue)) { throw "$tool was not found in PATH." }
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}
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$createClipPath = Join-Path $PSScriptRoot 'Create-Clip.ps1'
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if (-not (Test-Path -LiteralPath $createClipPath -PathType Leaf)) {
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throw "Create-Clip.ps1 was not found next to this script: $createClipPath"
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}
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$videoPath = Resolve-VideoPath -Path $Video
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[object[]]$tokens = @()
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if ($null -ne $ExtraArgs) { $tokens = @($ExtraArgs) }
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$extraParams = ConvertTo-ClipArgument -Tokens $tokens
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foreach ($reserved in 'Video', 'Frames', 'Suffix', 'Target') {
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if ($extraParams.ContainsKey($reserved)) {
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throw "-$reserved is managed by Create-Scenes.ps1 and must not be passed as an extra parameter."
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}
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}
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$info = Get-VideoInfo -Path $videoPath
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$changeTimes = @(Get-SceneChangeTime -Path $videoPath -Threshold $Scene)
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$scenes = @(Get-SceneList -Info $info -ChangeTimes $changeTimes -Template $Suffix)
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$scenes | Format-Table -AutoSize | Out-Host
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if ($List) { return }
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$confirm = [bool]$PSBoundParameters['Confirm']
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$pattern = Get-SceneFilePattern -VideoPath $videoPath -Template $Suffix
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Remove-ExistingScene -VideoPath $videoPath -Pattern $pattern -WhatIf:$WhatIfPreference -Confirm:$confirm
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$failures = 0
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foreach ($clipScene in $scenes) {
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$frames = '{0}-{1}' -f $clipScene.StartFrame, $clipScene.EndFrame
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Write-Verbose ('Scene {0}: frames {1}, suffix {2}' -f $clipScene.Index, $frames, $clipScene.Suffix)
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# Extra parameters are forwarded as the original token array, not as the hashtable: Create-Clip.ps1
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# collects unknown parameters through ValueFromRemainingArguments and parses them itself, while a
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# hashtable splat would hand it '-Name:value' tokens it does not understand.
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try {
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& $createClipPath -Video $videoPath -Frames $frames -Suffix $clipScene.Suffix -WhatIf:$WhatIfPreference -Confirm:$confirm @tokens
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if ($LASTEXITCODE -ne 0) { throw "Create-Clip.ps1 exited with code $LASTEXITCODE" }
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}
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catch {
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Write-Warning ('Scene {0} failed: {1}' -f $clipScene.Index, $_.Exception.Message)
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$failures++
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}
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}
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if ($failures -gt 0) { throw "$failures scene(s) failed to create." }
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