The MediaRecorder API enables you to record audio and video from a web app. It's available now in Firefox and in Chrome for Android and desktop.
From Chrome 48 on desktop and Android, VP9 will be an optional video codec for video calls using WebRTC.
Media Source Extensions (MSE) provide extended buffering and playback control for the HTML5 audio and video elements. While originally developed to facilitate Dynamic Adaptive Streaming over HTTP (DASH) based video players, MSE can be used for audio; specifically for gapless playback.
Hardware video support brings efficient decoding to plugins as well as HTML5 video. Flash users should switch from the old style Video to the StageVideo object.