Zencoder
Zencoder is the creator of an open-source HTML5 video player, Video.js, built with Javascript, HTML, and CSS. Video.js plays video via native playback in all HTML5 browsers and devices, or through Adobe Flash when HTML5 playback is not available.
Comparison of HTML5 and Flash
"HTML5" in this article sometimes refers not only to the HTML5 specification, which does not itself define ways to do animation and interactivity within web pages, but to HTML5 and related standards like JavaScript or CSS 3. Animation via JavaScript is also possible with HTML 4.