l
lorentedford@gmail.com
In CS2, Allstar downloads the
.dem
file (via Valve API or Faceit match endpoints), uses an open-source parser (like
democs
or
manta
) to extract tick events, and queues the demo to headless CS2 game instances to record high-resolution camera angles.
To achieve this exact cloud-render workflow in Fortnite, Allstar would need to adapt to Unreal Engine's replay architecture. Below are the technical specifications you can supply in your feature request.
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### Suggested Details Text
Architecture: Replicating Allstar’s CS2 Pipeline for Fortnite
Allstar’s CS2 pipeline relies on two components:
tick/event parsing
and
cloud headless rendering
. Replicating this for Fortnite requires targeting Unreal Engine's Local File Streamer (
.replay
) format:
1. Automated Demo Ingestion
* Unlike CS2's public match URLs, Fortnite
.replay
files reside locally on the client machine:
%LOCALAPPDATA%\FortniteGame\Saved\Demos\
* The Allstar Desktop Companion should implement an
I/O FileSystemWatcher
to monitor this directory. When the game client releases the file lock after match end (typically 15–30 MB), the agent auto-uploads the binary stream to Allstar’s S3/GCS ingestion bucket.
2. Fast-Path Event Parsing (Without Full NetField Decoding)
* In CS2, parsing tick-by-tick network data is heavy, but reading match headers and user events is fast. Fortnite’s
.replay
file layout functions identically:
*
File Structure:
Replay Header $\rightarrow$ Checkpoints (World baseline snapshots compressed via Oodle) $\rightarrow$ Replay Chunks / Packets $\rightarrow$
Event Metadata Chunks
.
*
Event Extraction:
Fortnite writes discrete, unencrypted event chunks containing user stats, player IDs, and the
Kill Feed
(
PlayerElimination
events) with millisecond timestamps and player GUIDs.
*
Implementation:
Instead of spending compute decompressing Oodle network packets for the entire 20-minute match, Allstar can scan specifically for
Event
chunk headers. If the user’s GUID matches the eliminator or downer, extract the timecode $(t)$ and register a highlight event at $[t - 10s, t + 5s]$.
3. Headless Cloud Playback & Clip Rendering
* CS2 clips are recorded by launching the client with
-insecure -novid +playdemo
. Fortnite provides equivalent Unreal Engine command-line demo tools:
* Running
FortniteClient-Win64-Shipping.exe -demoplay="<replay_name>" -demoscrub=<time_in_seconds> -demopause
allows automated seeking.
* Virtual production / spectator cameras can be bound via standard Unreal console arguments or automation plugins, dumping frames via Unreal's Movie Render Queue / offscreen render target to FFmpeg.
4. Solving the "Engine Version Deprecation" Bottleneck
*
The Problem:
Epic deprecates
.replay
files every bi-weekly game patch due to network protocol updates (
NetworkVersion
mismatch).
*
The Allstar Solution:
  1. Parse event chunks immediately upon upload (under 2 seconds).
  2. Queue the demo in the cloud render farm with priority before Tuesday scheduled patches.
  3. Archive client builds in containerized headless VMs so older replays can still be replayed against their corresponding engine version binaries.