In the meantime, there's no really reliable standard, cross-platform and cross-browser way to play back audio or video in the browser as major browser vendors still cannot agree on a single codec that would work everywhere.
That magical method of playing audio or video has never existed, though. The elimination of the Silverlight plugin (and mobile Flash!), neither of which were reliable cross platform/cross-browser, should speed up the efforts put in to finding such a perfect solution.
