How to improve this Powershell script? - powershell

Question

I wrote a powershell script that merges go pro video files if they have multiple files. It works when the videos are at the root drive i.e. C:, but otherwise not. The mergevideos.txt file is not created if I run the script from a different directory. Or the txt is created but it's empty. Not sure what's going on when run from a different directory.
So is there a way to fix these issues and refactor this code to make it better? Ideally I want the script to automatically look at the directory it's in or allows me to specify the directory it should work in so I can just call it from the same location but the videos can be anywhere.
$path = "C:/NewVideos/"
$oldvids = Get-ChildItem -Path $path *.mp4
foreach ($oldvid in $oldvids) {
$curpath = $oldvid.DirectoryName
$name = [System.IO.Path]::GetFileNameWithoutExtension($oldvid)
$ext = [System.IO.Path]::GetExtension($oldvid)
if ($name.StartsWith("GX01") -and !($name.EndsWith("_merged")))
{
$newvid = $curpath + $name + "_merged" + $ext
if ([System.IO.File]::Exists($newvid))
{
Write-Output "$name | ALREADY MERGED"
continue
}
$count = 1
for ($num = 2; $num -lt 10; $num++)
{
$nextpart = $name.Replace("GX01", "GX0" + $num)
if ([System.IO.File]::Exists($curpath + "/" + $nextpart + $ext))
{
$count = $num
}
}
if ($count -eq 1)
{
Write-Output "$name | SINGLE VIDEO"
continue
}
$mergefile = $curpath + "mergevideos.txt"
if (!(Test-Path $mergefile))
{
New-Item -path $curpath -name mergevideos.txt -type "file"
}
Clear-Content $mergefile
for ($num = 1; $num -le $count; $num++)
{
$nextpart = $name.Replace("GX01", "GX0" + $num)
$videofilename = "file '" + $nextpart + $ext + "'"
Add-Content $mergefile $videofilename
}
Write-Output "$name | MERGING $count VIDEOS"
ffmpeg -f concat -safe 0 -i $mergefile -c copy $newvid
}
}