There are two possible implementations of products video in Magento Framework templates:
Video is inserted through the admin panel via product’s option
1. Login to your Magento admin panel.
2. Go to Catalog->Manage Products click a needed product.
3. On General tab you will see Video URL option. Just paste a link to your video.
Video is inserted in code
1. Open the file app\design\frontend\default\themeXXX\template\ajax\catalog\product\view.phtml
2. Scroll to the bottom and find the video link.
3. Open the link with your video and copy the code for Embed button.
4. Paste your video link instead of existing one.
5. Save the file and refresh your website.
Feel free to check the detailed video tutorial below: