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PYCABAC

[Easy|Educational|Extensible|Experimental] CABAC

A Python port to the VTM CABAC engine

Prerequisites

Linux, macOS

  • Compiler with C++11 support
  • CMake >= 2.8.12

Windows

  • Visual Studio 2015
  • CMake >= 3.1

Installation

Just clone this repository and install via pip. Note the --recursive option which is needed for the pybind11 submodule:

git clone --recursive https://github.com/IENT/PyCabac.git
pip install .

With the setup.py file included in this example, the pip install . command will invoke CMake and build the pybind11 module as specified in CMakeLists.txt.

Note: We recommend the usage of a virtual environment:

python3 -m venv venv
source venv/bin/activate

Note: Uninstall via:

pip uninstall pycabac

In order to be able to run the unit tests, numpy is required:

pip install numpy

Demo

We expect that you are familiar with the concept of binary arithmetic coding. Hence, from a user perspective, it is most probably sufficient to understand how you can encode a binary sequence with PyCabac. For demos, check the Python scripts in either the demo or the tests folder:

  • demo/tracing.py demonstrates how to trace the encoding process of a binary sequence. Both the MPS and the probability of the current context can be extracted for each context.
  • tests/test_cabac.py shows how to encode integer symbols given a specific binarization or encode binary sequences directly.
  • tests/test_cabac_timing.py shows different ways of encoding an integer sequence and measures encoding/decoding time for comparison.
  • tests/test_cabac_sequence.py shows how to encode an integer sequence given a specific binarization and a predefined context set.

For a more technical/scientific description of the probability modelling in CABAC, you may want to have a look at:

H. Schwarz et al., "Quantization and Entropy Coding in the Versatile Video Coding (VVC) Standard," in IEEE Transactions on Circuits and Systems for Video Technology, doi: 10.1109/TCSVT.2021.3072202.

Pybind11 Example

import pybind11_example
pybind11_example.add(1, 2)

Python Unit Tests

Python unit tests are done using Python's built-in unittest module. Note that numpy is required. Python unit tests live in the tests folder. As long as all of your files match 'test*.py', unittest will automatically discover them. Run python3 -m unittest discover [--verbose] to run all unit tests.

C++ Unit Tests

C++ unit tests are done using Catch2 (https://github.com/catchorg/Catch2). C++ unit tests live in the tests folder. The tests executable can be built with CMake. On Linux/macOS use the following commands to build the tests executable:

mkdir build
cd build
cmake .. -DCMAKE_BUILD_TYPE=Release
make --jobs

This will leave the tests executable under build/tests/tests.

Citation

If you use this software, please cite it as below.

@inproceedings{RoMeScVo23,
  author = {Rohlfing, Christian and Meyer, Thibaut and Schneider, Jens and Voges, Jan},
  title = {Python Wrapper for Context-based Adaptive Binary Arithmetic Coding},
  booktitle = {Visual Communications and Image Processing {VCIP}~'23},
  address = {Jeju, South Korea},
  year = {2023},
  month = dec,
  doi = {10.1109/VCIP59821.2023.10402639},
  publisher = {{IEEE}, Piscataway}
}

Who do I talk to?

Jan Voges <[email protected]>

Christian Rohlfing <[email protected]>

Jens Schneider <[email protected]>