Regardless of what parameters I use the video takes up the full width of my page.
Please see virtuemart product page
www.cdswebtest.com/Sample_Site/index.php/shop/folders-inserters/fd-6204-basic-1-folder-inserter-detailhttp://www.cdswebtest.com/Sample_Site/index.php/shop/folders-inserters/fd-6204-basic-1-folder-inserter-detail

This is supposed to be 300 x 225 pixels.

I have also inserted it in Joomla article here
www.cdswebtest.com/Sample_Site/index.php/about-us

Both pages work fine on my phone (responsive).