x264 - a free h264/avc encoder

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), Måns Rullgård, Radek Czyz, Christian Heine (asm), Alex Izvorski, Alex Wright and Jason Garrett-Glaser.

It is released under the terms of the GNU GPL.

Development status

8x8 and 4x4 adaptive spatial transform
Adaptive B-frame placement
B-frames as references / arbitrary frame order
CAVLC/CABAC entropy coding
Custom quantization matrices
Intra: all macroblock types (16x16, 8x8, 4x4, and PCM with all predictions)
Inter P: all partitions (from 16x16 down to 4x4)
Inter B: partitions from 16x16 down to 8x8 (including skip/direct)
Interlacing (MBAFF)
Multiple reference frames
Ratecontrol: constant quantizer, constant quality, single or multipass ABR, optional VBV
Scenecut detection
Spatial and temporal direct mode in B-frames, adaptive mode selection
Parallel encoding on multiple CPUs
Predictive lossless mode
Psy optimizations for detail retention (adaptive quantization, psy-RD, psy-trellis)
Zones for arbitrarily adjusting bitrate distribution

The latest x264 source code can always be found by anonymous Git repository:

# git clone git://git.videolan.org/x264.git

You can browse the source on-line.

Unofficial builds for Windows are available from Jarod, techouse, or Sharktooth.

For support information and to ask questions, you have the following possibilities:

A mailing list (x264-devel), a forum (Doom10), and IRC (#x264@freenode).

Please report any bugs to the mailing list. If it is a crash, then compile x264 with `./configure --enable-debug` and follow the ffmpeg bugreporting guidelines.

If you use x264 in another project, let us know !

2005 December 26 -- x264 won Doom9's 2005 codec shoot-out, passing Ateme by a hair.

2005 December 12 -- x264 tied for 1st place (with Ateme) in the second annual MSU MPEG-4 AVC/ H.264 codecs comparison.