OBS Studio Livestreaming Setup

CastSprint was engineered from day one for esports livestreamers. Instead of introducing buggy third-party OBS plugins or virtual webcams that drop frames, CastSprint integrates directly with OBS Studio using native OS graphics capture APIs for zero-copy GPU memory sharing and discrete game audio isolation.

Direct GPU Memory Sharing (Zero CPU Readback)

On Windows 10/11, CastSprint utilizes Windows Graphics Capture (WGC). On macOS, it leverages ScreenCaptureKit. In both cases:

• Video frames pass directly from GPU VRAM to OBS without copying back to CPU RAM.
• Zero tearing, smooth 60 FPS pacing, and less than 1% CPU utilization in OBS.
• Other windows can overlap CastSprint on your desktop without obstructing the stream.

Step-by-Step Video Capture Setup

1. Launch CastSprint and start your mobile mirroring session.
2. In OBS Studio, locate the Sources dock and click the + button.
3. Select Window Capture and name it Mobile Game Stream.
4. Configure the properties:
   • Window: Select [castsprint_receiver.exe]: CastSprint — Gaming View (Windows) or [CastSprint]: CastSprint (Mac).
   • Capture Method: Select Windows 10 (1903 and up) on Windows.
   • Window Match Priority: Match title, otherwise find window of same executable.
   • Capture Cursor: Unchecked (prevents desktop mouse pointer from overlaying phone touch controls).
5. Click OK.

Gaming View & Borderless F11

To ensure your stream captures only the pristine mobile game feed:

• Press F11 in CastSprint to toggle borderless fullscreen.
• Alternatively, switch to the Gaming View tab in the desktop receiver.
• All navigation headers, sidebars, and diagnostic controls disappear, leaving a clean edge-to-edge mobile stream.

Isolated Game Audio Capture

To stream mobile game sound without capturing Discord calls, Spotify music, or desktop notification chimes:

1. In OBS Sources dock, click + and select Application Audio Capture (BETA).
2. Name the source Game Audio (CastSprint).
3. In the Window dropdown, select [castsprint_receiver.exe]: CastSprint.
4. Click OK.

Aspect Ratio & Canvas Alignment

Modern smartphones use ultrawide aspect ratios like 20:9 or 19.5:9 (e.g. 2400×1080 or 2796×1290), whereas YouTube and Twitch use 16:9 (1920×1080).

• In OBS, right-click the game source > Transform > Fit to screen (Ctrl+F or Cmd+F).
• This centers your mobile gameplay with clean letterboxing / pillarboxing.
• Place your webcam overlay, stream chat, and sponsor logos in the side margins!

Hardware AV Sync & Calibration

CastSprint incorporates monotonic hardware clock alignment (AvSynchronizer). If your audio output equipment (e.g., Bluetooth headphones or virtual mixers) introduces latency:

• Press [ to decrease audio delay by 10 ms.
• Press ] to increase audio delay by 10 ms.
• Current offset displays on the Stream Settings tab.

Stream Encoder & Bitrate Settings