RASR (RWTH ASR)

RASR is the RWTH Aachen University speech recognition toolkit, developed by the Machine Learning and Human Language Technology Group at the Chair for Computer Science 6, RWTH Aachen University (formerly: Human Language Technology and Pattern Recognition).

It contains tools and libraries for building automatic speech recognition systems, including acoustic-model training, decoding, lattice processing, feature extraction and related speech-processing workflows.
It is primarily intended for research and advanced ASR experimentation.

Requirements

RASR can either be built directly on the host system or inside one of the provided Apptainer images.

For a native build, the following tools and libraries are required:

• CMake >= 3.22
• a C++ compiler with C++20 support, for example GCC or Clang
• Bison
• libxml2
• BLAS/LAPACK, for example OpenBLAS
• zlib
• libsndfile

Depending on the enabled modules and tools, additional dependencies may be required, for example TensorFlow, ONNX Runtime, CUDA, OpenMP, FFmpeg, OpenFST or FLAC, and Python 3, NumPy and pybind11 for LibRASR. Modules and tools can be enabled or disabled through CMake options, see cmake_resources/Modules.cmake.

Apptainer images

For reproducible builds, especially on HPC systems, the repository provides Apptainer definitions in apptainer/. These images contain preconfigured build environments for common RASR setups, including TensorFlow/ONNX-based configurations.

Use one of these images if you do not want to install all build dependencies manually on the host system.

Building

Configure and build RASR with CMake:

cmake -S . -B build

creates the build system in the directory build/.
Useful options:

• -G Ninja to use Ninja as build system (usually faster)
• -DCMAKE_EXPORT_COMPILE_COMMANDS=1 to generate file compile_commands.json which can be used for parsing the project by some LSPs
• -DMODULE_<NAME>=0 to disable a module, for example -DMODULE_TENSORFLOW=0 -DMODULE_LM_TFRNN=0 to disable TensorFlow
• -D<TOOL>=0 to disable a tool, for example -DLibRASR=0 to disable LibRASR
• -DCMAKE_BUILD_TYPE=<type> to select the build type. Supported values are standard, debug and release. For example, use -DCMAKE_BUILD_TYPE=debug to build with debug flags. If unset, RASR uses standard.

cmake --build build

compiles the project. Use the flag --parallel for parallel builds and --target <NAME> for compiling only a certain target and its dependencies.

cmake --install build

installs the executables and libraries in arch/.... The installation prefix can be changed with --prefix.

Documentation

Additional documentation is available in doc/.

License and citation

RASR is distributed under the RWTH ASR license. See RWTH-ASR-License.txt for details. If you publish results obtained with RASR, please cite the publication listed in the license file.

(c) 2000-2026 RWTH Aachen University, Lehrstuhl fuer Informatik 6
http://www-i6.informatik.rwth-aachen.de/rwth-asr/
rwthasr@i6.informatik.rwth-aachen.de