x264 is a free library for encoding H264/AVC video streams. The code is written from scratch by Laurent Aimar, Loren Merritt, Eric Petit(OS X), Min Chen (vfw/asm), Justin Clay(vfw), Mns Rullgrd, Christian Heine (asm), and Alex Izvorski (asm).
Features:
CAVLC/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/direct)
Ratecontrol: optional VBV, single or multipass ABR, constant quantizer
Scene cut detection
Adaptive B-frame placement
B-frames as references / arbitrary frame order
8x8 and 4x4 adaptive spatial transform
Lossless mode
Custom quantization matrices
Parallel encoding of multiple slices
Note: x264 is still in early development stage.
What's New in version r906:
Fix and enable I_PCM macroblock support
In RD mode, always consider PCM as a macroblock mode possibility
Fix bitstream writing for PCM blocks in CAVLC and CABAC, and a few other minor changes to make PCM work.
PCM macroblocks improve compression at very low QPs (1-5) and in lossless mode.
