# gpu screen recorder
This is a screen recorder that has minimal impact on system performance by recording a window using the GPU only,
similar to shadowplay on windows. This is the fastest screen recording tool for Linux.
This screen recorder can be used for recording your desktop offline, for live streaming and for nvidia-like instant replay,
where only the last few seconds are saved.
Might now work when using a compositor such as picom when using the glx backend. Using the xrender backend with picom fixes this issue.\
Does not work when using gtk client side decorations (such as on Pop OS). Either disable those (if possible), install gtk-nocsd or record the whole monitor/screen if you have NvFBC.\
NvFBC doesn't work with PRIME, so if you are using PRIME then you can't record the monitor/screen, you have to record a single window.\
If you are using a variable refresh rate monitor, then choose to record "screen-direct". This will allow variable refresh rate to work when recording fullscreen applications. Note that some applications such as mpv will not work in fullscreen mode. A fix is being developed for this.
When recording Legend of Zelda Breath of the Wild at 4k, fps drops from 30 to 7 when using OBS Studio + nvenc, however when using this screen recorder the fps remains at 30.\
When recording GTA V at 4k on highest settings, fps drops from 60 to 23 when using obs-nvfbc + nvenc, however when using this screen recorder the fps only drops to 55.\
It is recommended to save the video to a SSD because of the large file size, which a slow HDD might not be fast enough to handle.
If you are running an Arch Linux based distro, then you can find gpu screen recorder on aur under the name gpu-screen-recorder-git (`yay -S gpu-screen-recorder-git`).\
If you are running an Ubuntu based distro then run `install_ubuntu.sh` as root: `sudo ./install_ubuntu.sh`.\
On other distros you need to install dependencies manually and run `build.sh`. Dependencies: `glew glfw3 cuda ffmpeg libx11 libxcomposite libpulse-simple`.\
Recording monitors requires a gpu with NvFBC support (note: this is not required when recording a single window!). Normally only tesla and quadro gpus support this, but by using [nvidia-patch](https://github.com/keylase/nvidia-patch) or [nvlax](https://github.com/illnyang/nvlax) you can do this on all gpus that support nvenc as well (gpus as old as the nvidia 600 series), provided you are not using outdated gpu drivers.
# How to use
Run `interactive.sh` or run gpu-screen-recorder directly, for example: `gpu-screen-recorder -w $(xdotool selectwindow) -c mp4 -f 60 -a "$(pactl get-default-sink).monitor" -o test_video.mp4`\
Then stop the screen recorder with Ctrl+C, which will also save the recording.\
Send signal SIGUSR1 (`killall -SIGUSR1 gpu-screen-recorder`) to gpu-screen-recorder when in replay mode to save the replay. The paths to the saved files is output to stdout after the recording is saved.\
There is also a gui for the gpu-screen-recorder called [gpu-screen-recorder-gtk](https://git.dec05eba.com/gpu-screen-recorder-gtk/).
[![Click here to watch a demo video on youtube](https://img.youtube.com/vi/n5tm0g01n6A/0.jpg)](https://www.youtube.com/watch?v=n5tm0g01n6A)
## How is this different from using OBS with nvenc?
OBS only uses the gpu for video encoding, but the window image that is encoded is sent from the GPU to the CPU and then back to the GPU. These operations are very slow and causes all of the fps drops when using OBS. OBS only uses the GPU efficiently on Windows 10 and Nvidia.\
This gpu-screen-recorder keeps the window image on the GPU and sends it directly to the video encoding unit on the GPU by using CUDA. This means that CPU usage remains at around 0% when using this screen recorder.
## How is this different from using FFMPEG with x11grab and nvenc?
FFMPEG only uses the GPU with CUDA when doing transcoding from an input video to an output video, and not when recording the screen when using x11grab. So FFMPEG has the same fps drop issues that OBS has.
* Support AMD and Intel, using VAAPI. cuda and vaapi should be loaded at runtime using dlopen instead of linking to those
libraries at compile-time.
* Clean up the code!
* Fix segfault in debug mode (happens because audio codec becomes NULL?)
* Dynamically change bitrate/resolution to match desired fps. This would be helpful when streaming for example, where the encode output speed also depends on upload speed to the streaming service.
* Show cursor when recording. Currently the cursor is not visible when recording a window and it's disabled when recording screen-direct to allow direct nvfbc capture for fullscreen windows, which allows for better performance and variable refresh rate monitors to work.
* Implement opengl injection to capture texture. This fixes composition issues and (VRR) without having to use NvFBC direct capture.
* Always use direct capture with NvFBC once the capture issue in mpv fullscreen has been resolved.