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liboac is the reference implementation of the Open Audio Codec (OAC) specification.
OAC intends to be the successor to Opus and liboac is based on libopus. Both are works in progress.
This package implements a shared library for encoding and decoding raw OAC bitstreams. It also includes a number of test tools used for testing the correct operation of the library. The bitstreams read/written by these tools should not be used for OAC file distribution: they include additional debugging data and cannot support seeking.
Modifications and additions made to the software by the Alliance for Open Media are licensed as specified in (COPYING)[./COPYING].
See the git commit logs for a list of modifications.
The libopus COPYING file is preserved as (OPUS_LICENSE)[./OPUS_LICENSE].
To build from a distribution tarball, you only need to do the following:
To build from the git repository, the following steps are necessary:
On an Ubuntu or Debian family Linux distribution:
On a Fedora/Redhat based Linux:
Or for older Redhat/Centos Linux releases:
On Apple macOS, install Xcode and brew.sh, then in the Terminal enter:
Clone the repository:
% git clone https://github.com/AOMediaCodec/oac.git % cd oac
Compiling the source
% ./autogen.sh % ./configure % make
On x86, it's a good idea to use a -march= option that allows the use of AVX2.
Install the codec libraries (optional)
% sudo make install
Once you have compiled the codec, there will be a oac_demo executable in the top directory.
input and output are little-endian signed 16-bit PCM files or OAC bitstreams with simple oac_demo custom framing.
This package includes a collection of automated unit and system tests which SHOULD be run after compiling the package especially the first time it is run on a new platform.
To run the integrated tests:
See cmake/README.md or meson/README.md.
This implementation uses floating-point by default but can be compiled to use only fixed-point arithmetic by setting --enable-fixed-point (if using autoconf) or by defining the FIXED_POINT macro (if building manually). The fixed point implementation has somewhat lower audio quality and is slower on platforms with fast FPUs, it is normally only used in embedded environments.
The implementation can be compiled with any compiler supporting C89 or later. While it does not rely on any undefined behavior as defined by C89 or C99, it relies on common implementation-defined behavior for two's complement architectures:
Right shifts of negative values are consistent with two's complement arithmetic, so that a>>b is equivalent to floor(a/(2^b)),
For conversion to a signed integer of N bits, the value is reduced modulo 2^N to be within range of the type,
The result of integer division of a negative value is truncated towards zero, and
The compiler provides a 64-bit integer type (a C99 requirement which is supported by most C89 compilers).