Add text to the end of specific file

I want to add a text (sample) to the end of specific file Before the Extension (in powershell or anything else)

for example:
file1.mp4 => file1(sample).mp4 ///
file2.mkv => file2(sample).mkv ///
and don’t do anything on other formats

tried this

Get-ChildItem *.mp4 | ForEach-Object {
    Rename-Item -Path $_.Name -NewName "$($_.Name) (sample)$($_.extension)" 
}

but it adds an addition file format to the name

>Solution :

Because .Name includes the extension. Try .BaseName which does not, e.g.:

-NewName "$($_.BaseName) (sample)$($_.extension)"