x264 is a free software library for encoding video streams into the H.264/MPEG-4 AVC format rv30: RealVideo 8, suspected to based largely on an early draft of H.264 (included with RealPlayer 8) rv40: RealVideo 9, suspected to be based on H.264 (included with RealPlayer 9) H.264/AVC/MPEG-4 Part 10 (Advanced Video Coding) is a standard for video compression