There were many bugs fixed since the 0.9 tag, particularly in rate control and Main10 mode decision. There have been a couple of minor performance improvements.

= Feature changes =

* Experimental support for 4:2:2
* improved profile and level detection
* imported checkasm-a.asm from x264 and fixed the asm bugs it exposed
* lookahead will use a worker thread when beneficial
* Many more motion candidate vectors are passed to motion estimation
* Lambda table improvements for better bitrate response at low QP

= API changes =

* added param.bEnableAccessUnitDelimiters
* removed param.vui.bEnableVuiParametersPresentFlag (now implied)
* removed param.vui.bEnableAspectRatioIdc (now implied)
* removed param.vui.bEnableVuiTimingInfoPresentFlag (always enabled)

= CLI changes =

–aud was added
–vui was removed
–timinginfo was removed (it is always enabled)