tf_crnn uses tensorflow-gpu package, which needs CUDA and CuDNN libraries for GPU support. Tensorflow GPU support page lists the requirements.

Using Anaconda

When using Anaconda (or Miniconda), conda will install automatically the compatible versions of CUDA and CuDNN

conda env create -f environment.yml

From this page:

When the GPU accelerated version of TensorFlow is installed using conda, by the command “conda install tensorflow-gpu”, these libraries are installed automatically, with versions known to be compatible with the tensorflow-gpu package. Furthermore, conda installs these libraries into a location where they will not interfere with other instances of these libraries that may have been installed via another method. Regardless of using pip or conda-installed tensorflow-gpu, the NVIDIA driver must be installed separately.