Today, Slideshare, the popular on-line presentation hosting site, completed its transition to using HTML5 instead of Flash for its eponymous slide sharing utlity.
Previously, browsers had to have Adobe Flash installed in order to view presentations on their site. However, with the advance of HTML5, and an increasing amount of traffic from (mobile) browsers without Flash support, the transition to HTML5 meant that SlideShare could be ahead of the competitors in terms of the delivery of components for other browsers.
Not only that, but the slides load 30% faster, and works in exactly the same way on both desktop computers as well as mobile devices such as the iPhone and iPad. A presentation, naturally in HTML5, explains more:
According to the engineering blog, there were a number of challenges in making this happen:
- Font conversion: if the browser doesn't support a particular font in the slideshow, it needs to be rasterised on the server and then downloaded to the browser as images.
- Text placement: to place text in exactly the same place involves figuring out where the PDF says it should be, and translating that to the position in the browser. Given the way that both systems handle font locations, getting text to appear in the right place was not an easily implementation.
- Cloud infrastructure: Since slideshare runs on Amazon EC2, instead of having each layer of a service hosted by different machines (potentially with latency for between-machine requests) they co-sited every service on every node, something they refer to as the Netflix "Rambo" architecture.
The blog notes that existing slides are being upgraded to HTML5 in the background, and that any new presentations uploaded will be converted to HTML5 by default. However, they note that this new architecture opens the possibility for interactive presentations (such as audio and video) which wasn't possible before.