x264 Video Codec

x264 Video Codec is a free library for encoding H264 or AVC video streams. The code is written from scratch by Laurent Aimar, Loren Merritt, Eric Petit(OS X), Min Chen (vfw or asm), Justin Clay(vfw), Mans Rullgard, Christian Heine (asm), and Alex Izvorski (asm). Some key features include CAVLC or CABAC, Multi-references, Intra: all macroblock types (16x16, 8x8, and 4x4 with all predictions), Inter P: all partitions (from 16x16 down to 4x4), Inter B: partitions from 16x16 down to 8x8 (including skip or direct), Rate control: optional VBV, single or multipass ABR, constant quantizer, Scene cut detection, Adaptive B-frame placement, B-frames as references or arbitrary frame order, 8x8, and 4x4 adaptive spatial transform, loss-less mode, custom quantization matrices, parallel encoding of multiple slices, and interlacing.