# Building Open RV on CentOS 7

## Summary

- [Summary](#summary)
- [Install Basics](#install-basics)
- [Install devtoolset-9](#install-devtoolset-9)
- [Install tools and build dependencies](#install-tools-and-build-dependencies)
  - [Install the python requirements](#install-the-python-requirements)
- [Install CMake](#install-cmake)
- [Install nasm](#install-nasm)
- [Install Qt](#install-qt)

## Install Basics

Make sure we have some basic tools available on the workstation:

```bash
sudo yum install sudo wget git
```

## Install devtoolset-9

By default the CentOS 7.9 built-in tools won't match the requirements we have to build RV. Install devtoolset-9 to remedy the situation.

```bash
sudo yum install centos-release-scl
sudo yum-config-manager --enable rhel-server-rhscl-7-rpms
sudo yum install devtoolset-9

# Note that you have to activate this all of the time (or add it to shell user initialization (e.g.: .bashrc))
scl enable devtoolset-9 $SHELL
```

## Install tools and build dependencies

Most of the build requirements can be installed using the following command:

```bash
sudo yum install alsa-lib-devel autoconf automake avahi-compat-libdns_sd-devel bison bzip2-devel cmake-gui curl-devel flex glew-devel libXcomposite libXi-devel libaio-devel libffi-devel ncurses-devel libtool libudev-devel libxkbcommon openssl-devel patch pulseaudio-libs pulseaudio-libs-glib2 mesa-libOSMesa mesa-libOSMesa-devel ocl-icd opencl-headers python3 python3-devel qt5-qtbase-devel readline-devel sqlite-devel tcl-devel tk-devel yasm zlib-devel
```

### Install the python requirements

Some of the RV build scripts requires extra python packages. They can be installed using the requirements.txt at the root of the repository.

```bash
python3 -m pip install -r requirements.txt 
```

## Install CMake

You need CMake version 3.24+ to build RV. The yum-installable version is not quite recent enough, you'll need to build and install CMake from source.

```bash
wget https://github.com/Kitware/CMake/releases/download/v3.24.0/cmake-3.24.0.tar.gz
tar -zxvf cmake-3.24.0.tar.gz
cd cmake-3.24.0
./bootstrap --parallel=32  # 32 or whatever your machine allows
make -j 32  # 32 or whatever your machine allows
sudo make install

cmake --version  # confirm the version of you're newly installed version of CMake
cmake version 3.24.0
```

## Install nasm

The `nasm` tool is required to build the `libdav1d` and `ffmpeg` dependencies.
The yum-provided version is slightly too old and you'll required building from sources.
Fortunately, building `nasm` from source is as easy as it gets:

```bash
wget https://www.nasm.us/pub/nasm/releasebuilds/2.15.05/nasm-2.15.05.tar.gz
tar xf nasm-2.15.05.tar.gz
cd nasm-2.15.05
scl enable devtoolset-9 "$SHELL -c './configure'" 
scl enable devtoolset-9 "$SHELL -c 'make -j'" 
sudo make install
```

## Install Qt

Download the last version of Qt 5.15.x that you can get using the online installer on the [Qt page](https://www.qt.io/download-open-source). Logs, Android, iOS and WebAssembly are not required to build OpenRV.

WARNING: If you fetch Qt from another source, make sure to build it with SSL support, that it contains everything required to build PySide2, and that the file structure is similar to the official package.