Currently Youtube and Vimeo do not support Dolby Digital Plus. We are working with both companies to allow users to upload content that includes a Dolby Digital Plus audio stream. Once this is available, we will let you know.
In the meantime, we've partnered up with online other video services that will play back Dolby Digital Plus to supported browsers, one of the benefits of this is if the input file is in 5.1 multichannel, these services will downstream a Dolby Digital Plus 5.1 to supported browsers
Check out the following URL http://vid.ly