Game capture and 2D replay for Echo Arena.

For record.py you need:

• aiohttp

For replay.py you need:

• pygame

Requires Python >= 3.6.

record.py [-h] [-f FRAMERATE] [-c CONCURRENCY] [-m MINSAVETIME]

This will start recording the current game immediately. It saves games when the current game ends and Echo VR switches to a different game. If you hit ^C at any time it will save what it has captured and then quit.

-f - target frame capture rate. Because the API is tied to the game loop, hitting this value will usually require tweaking various things. See the section on this below.

   Note that the capture rate recorded in the save file is the actual
   achieved rate, not the target rate.

-c - number of concurrent API requests to make. Adjusting this has counterintuitive effects. See the section on this below.

-m - minimum number of seconds that must be captured for a save file to be written to disk. Default 5.

A variety of factors influence the achieved capture rate.

• GPU vsync - if this is on, for various reasons Echo, and consequently your API capture, will usually end up locked to the desktop display refresh rate. Turn it off in your GPU settings if you want to capture above that rate.
• GPU perf - Echo's maximum framerate is determined by how good your GPU is.
• Concurrency - concurrent API requests will increase frame times for the game itself. 64 concurrent requests drop it to below 30fps on my R7 1800x / 1080ti.
• Num. CPU cores - can't tweak this, but it impacts what various -c values do.

The best thing to do is to keep -f fixed, start with -c 2, and increase it by 2 until the desired rate is reached. Keep in mind that the achieved rate does not vary linearly with -c value, e.g. -f 90 -c 2 may yield 60fps, -f 90 -c 4 30fps, and -f 90 -c 6 90fps.

The save format is very simple. It is a gzipped plaintext JSON file, UTF-8 encoded. The JSON has the following format:

{
    "caprate": <float>,
    "nframes": <int>,
    "frames": [
        <frame0>,
        <frame1>,
        ...
        <frameN>
    ]
}

Each frame is exactly as it was retrieved from the Echo VR API. The frames array is time-ordered.

• caprate is the capture rate of the save
• nframes is the length of the frames array
• frameN is the complete Nth API response

Loading the save file is trivial, e.g in Python:

import gzip

with gzip.open("mysavefile.json.gz", "r") as f:
    savedgame = json.load(f)

./replay.py SAVEFILE

This should open a pygame window with a cute 2D replay of the captured game.

Possession is indicated with a green circle inside the possessing player's circle. Goal positions are approximate.

Currently probably broken.