x264 - a free h264/avc encoder

x264 is a free software library and application for encoding video streams into the H.264/MPEG-4 AVC format, and is is released under the terms of the GNU GPL.

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.

x264 Overview

It provides best-in-class performance, compression, and features.
Performance-wise, x264 can encode 4 or more 1080p streams in realtime on a single consumer-level computer.
Quality-wise, x264 has the world's most advanced psychovisual optimizations and has won many awards, .
Feature-wise, x264 supports features necessary for many different applications, such as television broadcast, Blu-ray, low-latency video applications, and web video.

x264 forms the core of many web video services, such as Youtube, Facebook, Vimeo, and Hulu. It is also used in television broadcast by companies such as Avail Media.

Development status

Encoder features

• 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

Getting x264

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

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

Or grab a daily tarball.

You can browse the source on-line.

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

Support

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

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

Bugs

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.

Software using x264

• Avidemux
• ELDER
• ffdshow
• ffmpeg
• GordianKnot
• Handbrake: a multi-platform, multithreaded DVD to MPEG-4 ripper/converter.
• LiVES
• MeGUI
• MEncoder
• pspVideo9
• RealAnime
• StaxRip
• TCVP
• VLC media player: a cross-platform video player and streaming solution.

People using x264

• Bits on the Run
• Google Video
• MobileASL
• Speed Demos Archive
• TASvideos

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

Awards

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.