how can i get the content length before piping

i want to get the length of the stream file before piping it to the writable stream.
`let video = ytdl(url,{filter: 'videoonly', quality:itag})`
i want to get the exact content length of the video that is selected by this code, the length we will get when we use 'progess' event.
`video.on('progess', (_, _, totalsize)=> console.log(totalsize))`