There's x264 for H.264 video encoding, but now an "x265" project has been started to ship an open-source library for H.265/HEVC video encoding.
MultiCoreWare has published the initial code to x265, an open-source project forming around the H.265 / HEVC video codec
that was approved back in January. H.265 High Efficiency Video Codec is the H.264 successor and is intended to accomodate larger screen resolutions with 8K UHD resolutions up to 8192 x 4320 and it also doubles the data compression ratio of H.264.
There's now an x265.org
web-site for the open-source project forming around this codec while MultiCoreWare has published their initial code for the open-source video encoder to BitBucket.org