ReplaySorcery

An open-source, instant-replay solution for Linux.

Back when I used to use windows I used AMD ReLive alot. It, and the nVidia version ShadowPlay Instant Replay, will constantly record the screen without using too much computer resources and at the press of a keycombo will save the last 30 seconds.

I wanted something like this for Linux...

I got tired waiting for someone else to do it.

What is wrong with OBS?

A lot of people online suggest using OBS's replay buffer feature. However this requires opening OBS and start recording. I do not know when something will happen that I want to share. Might not even happen while playing a game. I just want something in the background (like a systemd service) so that whenever something happens I can record it.

Why JPEG? Why not hardware-accelerated encoding?

You might notice that this uses JPEG to encode frames. Initially the plan was to use hardware-accelerated encoding. However, since there is currently no way to grab frames directly on the GPU, sending frames to the GPU and encoded packets back became a huge bottleneck that limited me to no more than ~40-50 FPS and lagged basically any game I tried playing. I changed plan of attack based on the idea that:

• most of the frames will probably get discarded so why bother working hard on them?
• we can reencode them properly when we need to save
• the inital encoding of the frames can be cheap and is more a form a memory-compression
• turns out that an image format from 1992 is very easy for modern computers

Thus, this program does use JPEG (specifically libjpeg-turbo) for encoding frames, but then switches to x264 when you want to save it.

Documentation

Installing

Arch

Sergey A. has setup an AUR package called replay-sorcery-git.

Building from Source

This project needs cmake, make and nasm (used by x264) for compiling. All dependencies (other than X11 development files) are built as part of the binary and statically linked in. Don't @ me it makes distribution easier.

$ git submodule update --init
$ cmake -B bin -DCMAKE_BUILD_TYPE=Release
$ make -C bin
$ sudo make -C bin install

Running

It can be enabled as a user systemd service:

$ systemctl --user enable --now replay-sorcery

Once it is running, just press Ctrl+Super+R to save the last 30 seconds.

You can also use systemd to look at the output:

$ journalctl --user -fu replay-sorcery

Configuration

The config files use the XDG base directory specification with a filename of replay-sorcery.conf. If you do not know what that means you can probably assume that the program will look for configuration files in the following spots:

• /etc/xdg/replay-sorcery.conf
• ~/.config/replay-sorcery.conf
• ./replay-sorcery.conf

The configuration files themselves are simple <key> = <value> # <optional comment> pairs. The available options are:

Key	Description	Default
offsetX	This, along with offsetY, width and height specify the rectangle of the display to read frames from.	0
offsetY	See offsetX	0
width	See offsetX	1920
height	See offsetX	1080
framerate	The framerate in which to record frames.	30
duration	The duration to record when saving, in seconds.	30
compressQuality	A value from 0-100 specifying the quality to use for JPEG compression	70
outputFile	The output file path to save to. Uses strftime formatting.	~/Videos/ReplaySorcery_%F_%H-%M-%S.mp4
preOutputCommand	A command to run before generating the output video. Can be empty for no command.
postOutputCommand	A command to run after generating the output video.	notify-send ReplaySorcery :Video saved!"

As an example configuration, here is the configuration I use (my primary monitor is a 1440p monitor which is to the right of a 1080p monitor):

offsetX = 1920
width = 2560
height = 1440
outputFile = ~/Videos/ReplaySorcery/%F_%H-%M-%S.mp4

Issues

• Code is a bit of a mess <_<

TODO

• Document code better
• Add audio support
  • For my personal requirements it would need to support hot plugging (I use a bluetooth headset).
  • Alot of the time visuals alone are enough to tell a story.
  • (not crossing it out entirely just might take time).
• Cross-platform support
  • Doubt there is any demand though
  • Maybe for Intel devices if they are fast enough?
• Smaller tweaks:
  • Add sound effect for when it saves
  • Add configuration option for changing hotkey
  • Allow downscaling before saving