OpenH264 is a codec library which supports H.264 encoding and decoding. It is suitable for use in real time applications such as WebRTC. See http://www.openh264.org/ for more details.

Encoder Features

- Constrained Baseline Profile up to Level 5.2 (4096x2304)

- Arbitrary resolution, not constrained to multiples of 16x16

- Rate control with adaptive quantization, or constant quantization

- Slice options: 1 slice per frame, N slices per frame, N macroblocks per slice, or N bytes per slice

- Multiple threads automatically used for multiple slices

- Temporal scalability up to 4 layers in a dyadic hierarchy

- Spatial simulcast up to 4 resolutions from a single input

- Long Term Reference (LTR) frames

- Memory Management Control Operation (MMCO)

- Reference picture list modification

- Single reference frame for inter prediction

- Multiple reference frames when using LTR and/or 3-4 temporal layers

- Periodic and on-demand Instantaneous Decoder Refresh (IDR) frame insertion

- Dynamic changes to bit rate, frame rate, and resolution

- Annex B byte stream output

- YUV 4:2:0 planar input

Decoder Features

- Constrained Baseline Profile up to Level 5.2 (4096x2304)

- Arbitrary resolution, not constrained to multiples of 16x16

- Single thread for all slices

- Long Term Reference (LTR) frames

- Memory Management Control Operation (MMCO)

- Reference picture list modification

- Multiple reference frames when specified in Sequence Parameter Set (SPS)

- Annex B byte stream input

- YUV 4:2:0 planar output

OS Support

- Windows 64-bit and 32-bit (initial release is only 32-bit, 64-bit will follow soon)

- Mac OS X 64-bit (initial release does not include this target, will follow soon)

- Linux 64-bit and 32-bit (initial release is only 32-bit, 64-bit will follow soon)

- Android 32-bit (initial release does not include this target, will follow soon)

- iOS 64-bit and 32-bit (not supported yet, may be added in the future)

Processor Support

- Intel x86 optionally with MMX/SSE (no AVX yet, help is welcome)

- ARMv7 optionally with NEON (initial release does not include this target, will follow later)

- Any architecture using C/C++ fallback functions

Using the Library

Linux makefiles for 32 bit builds are available:

: build the decoder library and executable via codec/build/linux/dec/makefile

: build the encoder library and executable via codec/build/linux/enc/makefile

: build the encoder shared library via processing/build/linux/makefile

Windows Visual Studio 2008/2010/2012 projects are available:

: build the decoder via the Visual Studio projects in codec/build/win32/dec

: build the encoder via the Visual Studio projects in codec/build/win32/dec

: build the encoder shared library via the Visual Studio projects in processing/build/win32/

NASM needed to be installed for assembly code: workable version 2.07 or above, nasm can downloaded from http://www.nasm.us/

API details to be provided later.

Using the Test App

Linux shell scripts to build the test apps:

: build via testbin/AutoBuild_Linux.sh

: clean via testbin/AutoClean_Linux.sh

Windows batch files to build the test apps:

: Visual Studio 2008 use testbin/AutoBuild_Windows_VS2008.bat

: Visual Studio 2010 use testbin/AutoBuild_Windows_VS2010.bat

: Visual Studio 2012 use testbin/AutoBuild_Windows_VS2012.bat

Usage information can be found in testbin/CmdLineReadMe

Command line options and details to be provided later.

Using the Source

codec - encoder, decoder, console (test app), build (makefile, vcproj)

processing - raw pixel processing (used by encoder)

testbin - autobuild scripts, test app config files, yuv test files

bin - binaries for library and test app

Known Issues

See the issue tracker on https://github.com/cisco/openh264/issues

- Encoder errors when resolution exceeds 3840x2160

- Encoder errors when compressed frame size exceeds half uncompressed size

- Encoder console app only support multiple of 16 width/height for now

- Decoder errors when compressed frame size exceeds 1MB

License

BSD, see LICENSE file for details.