我是网络开发的新手，我的问题是，据我所理解的以下代码，它将打开Chrome Video Player，该视频播放器还有一个下载按钮，可以下载视频。
如何获取以mp4扩展名结尾的视频的真实网址？
<video loop muted playsinline autoplay="autoplay" preload width="640" height="360">
<source src="https://r4---sn-nv47lney.googlevideo.com/videoplayback?lmt=1517456704789231&key=cms1&dur=386.240&ipbits=0&requiressl=yes&mime=video%2Fmp4&source=youtube&pl=20&itag=18&ei=hudyXP-4OIXlwQHBsaOwAw&gir=yes&expire=1551055847&ratebypass=yes&c=WEB&fvip=4&id=o-AHZWBPA4mUtFjI305r97oXdDZELtWbNS5dJeuwGAqirn&clen=23249888&ip=2600%3A3c00%3A%3Af03c%3A91ff%3Afe52%3Af0d3&sparams=clen,dur,ei,expire,gir,id,ip,ipbits,ipbypass,itag,lmt,mime,mip,mm,mn,ms,mv,pl,ratebypass,requiressl,source&signature=41173E731E2CFF1D3BB61936B8A78716C9515442.358D2657A715DA85E175DB497BC6D211489DA79E&title=Very+Powerful+Motivational+Video+For+Medical+Students.+Goosebumps+Guaranteed!!!&redirect_counter=1&rm=sn-q4fels76&req_id=4c1bf6c1b1eb36e2&cms_redirect=yes&ipbypass=yes&mip=192.123.1.4&mm=31&mn=sn-nv47lney&ms=au&mt=1551034152&mv=m#t=0.9" type="video/mp4" />
</video>