Open Broadcaster Software is free and open source software for video recording and live streaming. Supported features include:
Encoding using H264 (x264) and AAC.
Support for Intel Quick Sync Video (QSV) and NVENC.
Unlimited number of scenes and sources.
Live RTMP streaming to Twitch, YouTube, DailyMotion, Hitbox and more.
File output to MP4 or FLV.
GPU-based game capture for high performance game streaming.
DirectShow capture device support (webcams, capture cards, etc).
Windows 8 high speed monitor capture support.
Bilinear or lanczos3 resampling.
OBS MultiPlatform is a complete rewrite of the original OBS from the ground up, with the main goals of course being multiplatform support, a more thorough feature set, and a much more powerful API. A very early and simple release is currently available for Mac.
OBS MultiPlatform will eventually support many of the advanced requested features not present in the original OBS, such as multiple stream outputs and scene previewing. It does not have these features in this release.