SubtitleTools

1.0.0

Public/ASS/Convert-AssToSrt.ps1

                                function Convert-AssToSrt {

    <#

    .SYNOPSIS

        Converts an ASS/SSA SubtitleFile to SRT format.

    .DESCRIPTION

        Strips all ASS override tags and converts the entries to SrtEntry objects.

        ASS line-break tokens (\N, \n) become real line breaks in the SRT output.

        HTML-style tags (<b>, <i>) in ASS text are preserved as SRT HTML tags.

    .PARAMETER InputObject

        A SubtitleFile with Format 'ASS' or 'SSA'.

    .PARAMETER StripFormatting

        Remove all formatting tags (both ASS override tags and HTML tags).

    .EXAMPLE

        Import-SubtitleFile 'anime.ass' | Convert-AssToSrt | Export-SubtitleFile -Path 'anime.srt'

    .EXAMPLE

        Import-SubtitleFile 'anime.ass' | Convert-AssToSrt -StripFormatting

    #>

    [CmdletBinding()]

    [OutputType('SubtitleFile')]

    param(

        [Parameter(Mandatory, ValueFromPipeline)]

        [SubtitleFile] $InputObject,

        [switch] $StripFormatting

    )

    process {

        $srtFile         = [SubtitleFile]::new()

        $srtFile.Format  = 'SRT'

        $srtFile.Encoding = 'UTF-8'

        $srtFile.Path    = $InputObject.Path -replace '\.(ass|ssa)$', '.srt'

        $i = 1

        foreach ($entry in $InputObject.Entries) {

            $srt             = [SrtEntry]::new()

            $srt.Index       = $i

            $srt.BlockNumber = $i

            $srt.Start       = $entry.Start

            $srt.End         = $entry.End

            $text = $entry.RawText

            # Convert ASS override tags to SRT HTML where possible, or strip them

            if ($StripFormatting) {

                $text = $text -replace '\{[^}]*\}', ''

            } else {

                # Map common ASS tags to SRT HTML equivalents

                $text = $text -replace '\{\\b1\}',  '<b>'

                $text = $text -replace '\{\\b0\}',  '</b>'

                $text = $text -replace '\{\\i1\}',  '<i>'

                $text = $text -replace '\{\\i0\}',  '</i>'

                $text = $text -replace '\{\\u1\}',  '<u>'

                $text = $text -replace '\{\\u0\}',  '</u>'

                # Strip remaining unmapped tags

                $text = $text -replace '\{[^}]*\}', ''

            }

            # Convert ASS line breaks

            $text = $text -replace '\\N', "`n"

            $text = $text -replace '\\n', "`n"

            $text = $text -replace '\\h', ' '

            $lines         = $text -split "`n"

            $srt.Lines     = $lines

            $srt.RawText   = $lines -join "`n"

            $srt.HasHtmlTags = $text -match '<(b|i|u)\b'

            $srtFile.Entries += $srt

            $i++

        }

        return $srtFile

    }

}