bash – yt-dlp — how to add ffmpeg conversion after download

I’m using a rather long yt-dlp command to download and convert the downloaded files into mp4 format. However, the resulting mp4 files sometimes cause problems. That’s why I would like to add a ffmpeg conversion directly after download. At the moment, I am using the following command:

alias ytdl="cd ~/Desktop; function _ytdl(){ yt-dlp -o "%(upload_date>%Y-%m-%d)s %(title)+.100U [%(id)s]" --download-archive /Users/admin/Documents/bin/ytdl_archive.txt --merge-output-format mp4 --no-check-certificates $1;};_ytdl"

The --merge-output-format mp4 option may not be necessary anymore. Instead I would like to add something like this:

... | ffmpeg -i nnn.nnn nnn.mp4

Is there any way to combine this into an alias, while keeping the elaborate filename?

Thanks a lot for any help,