# GCV
OpenGL/OpenCL/VAAPI interop demos (aka. run it on the GPU!) using the 4.x branch of OpenCV (https://github.com/opencv/opencv/tree/4.x)

The goal of the demos is to show how to use OpenCL interop in conjunction with OpenCV on Linux to create programs that run mostly (the part the matters) on the GPU. 

The author of the example video (which is also used for the demos videos in this README) is **(c) copyright Blender Foundation | www.bigbuckbunny.org**.

# Hardware requirements
* Support for cl_khr_gl_sharing and cl_intel_va_api_media_sharing OpenCL extensions.
* Support for OpenCL 2.0
* If you are on a recent Intel Platform (Gen8 - Gen12) you probably need to install an alternative [compute-runtime](https://github.com/kallaballa/compute-runtime)

There are currently five demos (**the preview videos are scaled down and highly compressed**):
## tetra-demo
Renders a rainbow tetrahedron on blue background using OpenGL and encodes to VP9

https://user-images.githubusercontent.com/287266/200169105-2bb88288-cb07-49bb-97ef-57ac61a0cfb8.mp4

## video-demo
Renders a rainbow tetrahedron on top of a input-video using OpenGL and encodes to VP9

https://user-images.githubusercontent.com/287266/200169164-231cb4d8-db5c-444b-8aff-55c9f1a822cc.mp4

## nanovg-demo
Renders a color wheel on top of a input-video using nanovg (OpenGL) and encodes to VP9

https://user-images.githubusercontent.com/287266/200169216-1ff25db5-f5e0-49d1-92ba-ab7903168754.mp4

## optflow-demo and optflow_mt-demo
My take on a optical flow visualization on top of a video. Encoded to VP9. "optflow_mt" is an example on how to use threads to maximize use of both GPU and CPU.

https://user-images.githubusercontent.com/287266/200512662-8251cf2c-23b3-4376-b664-d3a85b42d187.mp4

# Instructions
You need to build the most recent 4.x branch of OpenCV.

## Build OpenCV

```bash
git clone --branch 4.x https://github.com/opencv/opencv.git
cd opencv
mkdir build
cd build
cmake -DCMAKE_BUILD_TYPE=Release -DHAVE_EGL_INTEROP=ON -DWITH_OPENGL=ON -DWITH_VA=ON -DWITH_VA_INTEL=ON -DWITH_QT=ON -DBUILD_PERF_TESTS=OFF -DBUILD_TESTS=OFF ..
make -j8
sudo make install
```

## Build demo code

```bash
git clone https://github.com/kallaballa/GCV.git
cd GCV
make -j2
```
## Download the example file
```bash
wget -O bunny.webm https://upload.wikimedia.org/wikipedia/commons/transcoded/f/f3/Big_Buck_Bunny_first_23_seconds_1080p.ogv/Big_Buck_Bunny_first_23_seconds_1080p.ogv.1080p.vp9.webm
```
## Run the tetra-demo:

```bash
src/tetra/tetra-demo
```

## Run the video-demo:

```bash
src/video/video-demo bunny.webm
```

## Run the nanovg-demo:

```bash
src/nanovg/nanovg-demo bunny.webm
```

## Run the optflow-demo:

```bash
src/optflow/optflow-demo bunny.webm
```

## Run the optflow_mt-demo:

```bash
src/optflow_mt/optflow-demo_mt bunny.webm
```