# FastCarPlay
This is C++ implementation of carplay receiver for "Autobox" dongles. 
The purpose of the project was to make application lightweight to run on Raspberry PI Zero 2W and use hardware decoding.

# Dongles
The dongles are readily available from Amazon or Aliexpress labeled by !["Carlinkit"](https://www.carlinkit.com/).
Devices might have different vendor and product id's. Check your with lsusb and update settings if necessary.

# Setup
## Dependencies
The project is based on SDL2, FFMPEG, LIBUSB. It use XXD for resource embedding.
```
sudo apt install build-essential xxd libsdl2-dev libsdl2-ttf-dev libavformat-dev libavcodec-dev libavutil-dev libswscale-dev libusb-1.0-0-dev
```
To run the application you also need to install runtime
```
sudo apt install ffmpeg libsdl2-2.0-0 libsdl2-ttf-2.0-0 libavformat59 libavcodec61 libavutil57 libswscale7 libusb-1.0-0
```

## Build and run
The application can be started with settings file. Sample of the settings file can be found in settings.txt
The project is using make. From the repository root run following
```
make clean
make release
./out/app ./settings.txt
```

## Customisation
You can change font and background images by replacing files in ./src/resource
- background.bmp for background image. Use BMP format only.
- font.ttf for font. Use TTF fdrmat only

The names of the file need to be exactly same. Resources are embedded in executable, remake the project to regenerate resources
```
make clean
make release
```

## Keys
The following keys have been mapped:
- Left - navigate left
- Right - navigate right
- Enter - select active item
- Backspace - Go back
- f - toggle fullscreen mode

# Status
What is working:
- Video
- Audio (multiple channels)
- Key navigation
- Simple touch

What is not working:
- Multi touch - i have no means to test it
- Microphone - that's next step for me to figure out how to feed sound
- Telephone - the listening part will work, but because there is no mic implementation you can't speak

## Notes
Regardless the resolution there are 2 types of settings
- source-width source-height source-fps - defines what video parameters will be requested from device
- width height fps - defines video drawing resolution and fps

The SDL will anyway scale the image to your screen/window size using internal HW scaling, so ideally you should use same values for width and height.
If the source parameters will be different the scaling will be applied, however that scaling is not hardware accelerated and can consume a lot of CPU.
You can set the 'scaler' in setting to define scaling algorithm. On my Raspbery Pi Zero 2W even easiest algorithm loads CPU to 100% and cause fram drop.

Increasing FPS above Source-FPS will cause app to run UI loop with less delays and do more event polling. This can increase responsivenes of the system, but also will make X11 to use more resources.

## Next plans
- Implement direct buffer transfer from video decoder to renderer (should reduce amount of memory copies and CPU load)
- Control audio buffers better (now system use 3 decoding threads but in reality only 2 required)
- Reduce music volume when there is navigation messages
- Add abilities to run script on device connect and device disconnect

# Acknowledgement
The project is inspired and based on great work done by other developers:
- ![pycarplay by electric-monk](https://github.com/electric-monk/pycarplay)
- ![carplay-receiver by harrylepotter](https://github.com/harrylepotter/carplay-receiver)
- ![react-carplay by rhysmorgan134](https://github.com/rhysmorgan134/react-carplay)

The project is licenced under GPL-3 licence. See LICENCE for details.
The project is using ![Open Sans](https://fonts.google.com/specimen/Open+Sans) font. See FONT_LICENCE for details.

# Finally
If you have any questions, suggestions or you find problems running this feel free to open issue.