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Set-FFMpegVideoSpeed.ps1

19 Sep 2025

Description

Purpose

Speed up a video file by a configurable percentage while keeping audio and video in sync.

Detailed Description

Set-FFMpegVideoSpeed wraps the ffmpeg setpts and atempo filters to produce a faster version of a video. Provide the full path to the source file and the desired output location, then specify the percentage increase. The function converts that percentage into a factor that ffmpeg uses to adjust both video frames and audio tempo, giving you a sped-up copy without touching the source file.

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Usage

Example 1

Set-FFMpegVideoSpeed -VideoFile "C:\\Media\\Clips\\demo.mp4" -OutputFile "C:\\Media\\Clips\\demo-fast.mp4" -SpeedUpPercentage 150

Creates a copy of the clip at 1.5x speed.

Example 2

Get-ChildItem -Path "C:\\Media\\Highlights" -Filter *.mp4 |
    ForEach-Object {
        $output = Join-Path $_.Directory.FullName ("{0}-fast{1}" -f $_.BaseName, $_.Extension)
        Set-FFMpegVideoSpeed -VideoFile $_.FullName -OutputFile $output -SpeedUpPercentage 200
    }

Batch processes highlight reels, doubling their playback speed while writing new files alongside the originals.

Example 3

Set-FFMpegVideoSpeed -VideoFile "C:\\Media\\Tutorials\\walkthrough.mkv" -OutputFile "C:\\Media\\Tutorials\\walkthrough-condensed.mkv"

Uses the default SpeedUpPercentage value (100) to keep tempo unchanged, which is handy when you only want to re-encode with the preset filters.

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Notes

  • Requires ffmpeg to be installed and present on the system PATH.
  • Ensure the output file extension matches the input container to avoid format issues.
  • For speeds greater than 200% you may need to adjust the atempo filter chain manually, as ffmpeg limits each atempo stage to a factor between 0.5 and 2.

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Script

<#
.SYNOPSIS
Speeds up a video file.

.DESCRIPTION
Speeds up a video file by a specified percentage, adjusting both video and audio to maintain synchronization. Useful for creating condensed versions of media or increasing playback speed for review purposes.

.PARAMETER VideoFile
Input video file. Full path.

.PARAMETER OutputFile
Output video file. Full path, and make sure that the file extension is the same as the input. Might not matter but why risk it?

.PARAMETER SpeedUpPercentage
Percentage to speed up the video by. 100% will be twice as fast, etc. Defaults to 100.

.EXAMPLE
Set-FFMpegVideoSpeed -VideoFile "C:\Users\Rob\OneDrive\Desktop\Black.Mirror.S01E01.720p.HDTV.x264-BiA.avi" -OutputFile "C:\Temp\out.avi" -SpeedUpPercentage 400

#>
function Set-FFMpegVideoSpeed {
    [CmdletBinding()]

    param (
        [Parameter(ValueFromPipeline = $false, HelpMessage = "Input video file. Full path.")]
        [string]$VideoFile,

        [Parameter(ValueFromPipeline = $false, HelpMessage = "Output video file. Full path, and make sure that the file extension is the same as the input. Might not matter but why risk it?")]
        [string]$OutputFile,

        [Parameter(ValueFromPipeline = $false, HelpMessage = "Percentage to speed up the video by. 100% will be twice as fast, etc. Defaults to 100.")]
        [int]$SpeedUpPercentage = 100
    )

    process {
        [decimal] $factor = ($SpeedUpPercentage / 100)

        ffmpeg -i "$VideoFile" -vf "setpts=(PTS-STARTPTS)/$factor" -crf 18 -af atempo=$factor $OutputFile
    }
}

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Download

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